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H.M. HasaneanMeteorology Department, Faculty of Meteorology, Environment and Arid Land Agriculture, King Abdulaziz University

Key Words: Middle East Meteorology, Arid and sub arid climate, Dust storm, Climate change, Circulation systems.

Contents

1. Introduction1.1 Middle East Definition1.2 Overview of the Middle East climate2. Regional climate in the Middle East climate 2.1 Climate of Egypt 2.2 Climate of the Arabian Peninsula an overview 2.2.1 Climate of Kingdom of Saudi Arabia 2.2.2 Climate of Oman 2.2.3 Climate of the United Arab Emirates 2.2.4 Climate of Qatar 2.2.5 Climate of Bahrain 2.2.6 Climate of Kuwait 2.2.7 Climate of Yemen 2.3 Climate of Syria 2.4 Climate of Lebanon 2.5 Climate of Jordan 2.6 Climate of Israel and Palestine 2.7 Climate of Cyprus 2.8 Climate of Iraq 2.9 Climate of Turkey 2.10 Climate of Iran3. Dust storms over the Middle East 3.1 Types of dust storm 3.2 Synoptic analysis of dust storm in the Middle East4. Climate change over the Middle East climate 5. Climate change impacts on water resources in Middle East6. Circulation systems affect the climate of the Middle East 6.1 Impact of the North Atlantic (NAO) on the Middle East climate 6.2 Impact of the El Nino Southern Oscillation (ENSO) on Middle East climate 6.3 The role of highs pressure (Siberian and Subtropical high pressure) and Indian Monsoon Low pressure on Middle East Climate 6.4 The role of Jets streams on Middle East climate7. Conclusion

Summary

MIDDLE EAST METEOROLOGY

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The Middle East is a region that spans southwestern Asia, western Asia, and northeastern Africa. Although much of the Middle East region has a Mediterranean climate type, i.e. Csa in the widely used Koeppen classification with wet winters and dry summers. Middle Eastern climatic conditions vary greatly, depending on the season and the geography. Although the hot arid, or desert, climate predominates in the region, the well-watered highlands of Turkey and the mountains of Iran and Ethiopia are important as sources of the region's major rivers.

The Middle East is as one of the regions most affected by dust, in the world, next to Africa. Dust or sand storms are caused by the outflow from low-pressure cells passing through a desert area from west to east. Sand storms can occur throughout the year in the Middle East, but the prime months are May-September.

The results of many researchers showed a linear warming across the Middle East. The maximum warming is occurring in the spring, and the minimum warming is occurring in the winter. Local and regional warming signal may be associated with human-induced desertification and overgrazing. The results of model in the 21st century show widespread warming, with a maximum in interior Iran during summer. It also found some cooling in the southeast Black Sea region during spring and summer that is related to increases in snowfall in the region. The results also show widespread decreases in precipitation over the eastern Mediterranean and Turkey, and increases were found over the southeast Black Sea, southwest Caspian Sea, and Zagros mountain regions during all seasons except summer. While the Saudi desert region receives increases during summer and autumn.

The variability of atmospheric circulation is the most important factor determining changes in spatial distribution of temperature, cloudiness, precipitation and other climatic elements. The North Atlantic Oscillation (NAO) atmospheric circulation pattern appears to exhibit a clear influence on the climate of the region on inter-annual and decadal timescales. Drier-than-average conditions prevail over parts of the Middle East during high NAO index winters. There is recent evidence that the El Niño/Southern Oscillation (ENSO) has influence on the climate of the Middle East in recent decades. El Niño conditions weaken the Indian monsoon and warm the Arabian Sea thus weakening the pressure gradient and reducing the wind speed. La Niña conditions make the pressure gradient stronger thus bringing more rainfall in the region. Anomalous temperature variations over the Middle East (cooling) associated with the stronger clockwise flow around the subtropical Atlantic high-pressure center. The oscillation and strength of Asiatic monsoon low pressure and subtropical high pressure play an important role in rainfall over the River Nile. The annual migration of the ITCZ and seasonal development of the monsoon winds are key-components of the climatology in the Indian Ocean and the surrounding areas.

Tropical Easterly jet stream was weakened in El Nino year and enhanced in La Nina year accompanying with the dry and wet condition respectively. Subtropical jet stream has affect on temperature and rainfall over Arabian Peninsula, where the core of the subtropical jet is stronger during the winter than the other seasons and located near 27.5oN, while it’s weaker during the summer and shifted north ward to appear at 43oN.The interaction between the polar front jet stream (PFJ) and subtropical jet stream (SJS) and its role in the surface cyclogenesis has been affected not only over the North African region but also over other subtropical regions.

1. Introduction1.1 Middle East Definition

The Middle East borders are not well established. The boundaries of this region change with changing topics. A different approach in defining the area is used in politics, geography, history, environment, economics, and so on. The term "Middle East" was popularized around 1900 in the United Kingdom (http://en.wikipedia.org/wiki/Middle_East#cite_note-1). The Middle East (or, formerly more common, the Near East (http://en.wikipedia.org/wiki/Middle_East#cite_note-0) is a

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region that spans southwestern Asia, western Asia, and northeastern Africa. The term refers collectively to the Asian countries of Bahrain, Cyprus, Iran, Iraq, Palestine, Israel, Lebanon, Oman, Qatar, Saudi Arabia, Syria, Turkey, the United Arab Emirates, and Yemen, and the African country of Egypt. Much of the Middle East is arid, and the region's topography features extensive desert areas, rugged mountains, and dry plateaus.  Water is in short supply, and agriculture often depends on expensive irrigation systems.  The Middle East map (Figure 1) identifies the primary countries of the Middle East and shows their national boundaries.

1.2 Overview of the Middle East climate In the Middle East, investigations of long-term variations and trends in temperature data are not

suffer serious environmental, agricultural and water resources problems, receiving enough attention even though, these countries. The Middle East is interesting for several reasons. The landscape has been massively altered by developing human activity over the last 8000 years, including forest removal, rangeland degradation by grazing and trampling, and watercourse damming and diversion. Due to rapid population growth, political conflict and water scarcity are common throughout the area, rendering it sensitive to changes in climate. A significant impact on the history of the region may be due to climate change. Although much of the Middle East region has a Mediterranean climate type, i.e. Csa in the widely used Koeppen classification (Oliver and Hidore, 1984) with wet winters and dry summers, the spatial gradients in climate are far sharper than in the broad prototype Csa region to the west. For example, along the 40°N meridian, the northward transition from desert (BWh) through steppe (BSh) to cool highland climate (H) occurs within 400 km. Elsewhere in the region, numerous coastlines and mountain ranges modify the local climates (Oliver and Hidore, 1984).

Middle Eastern climatic conditions vary greatly, depending on the season and the geography. The basic climate of the Middle East can be characterized in two words: hot and dry, although winters are mild with some rain. The exception is the mountains, where desert turns to steppe in northern Iraq, northern Iran and eastern Turkey. Winters here can be severe. The Arabian Peninsula has among the hottest and driest conditions found anywhere in the world. The hot desert conditions induce a strong seasonal wind pattern in the region, known as the monsoon. Although we often associate "monsoon" with flooding rains, it comes from an Arabic word meaning "season". During the summer, winds blow unabated toward the hot interior of the Arabian Peninsula, whereas in winter, the winds are in the south and blow off the land. In northern regions, continental winds usher in cold Siberian air which wrings some rain and snow out of the sky along the coasts. Across the Middle East, summer temperatures are usually around 29°C (84.2°F), but often soar above 38°C (100.4°F). In Baghdad, the record high is 49°C (120.2°F); in Basra, 51°C (123.8°F), the highest temperatures recorded in any major Middle Eastern city. In the Saudi desert, however, temperatures over 49°C (120.2°F) are common. Most storms crossing the Middle East become dust- or sandstorms when strong winds whip the dry desert surface; as many as 38 occur annually.

Precipitation on the semiarid margins of Middle Eastern deserts ranges from 14 inches (350 mm) to 30 inches (750 mm) annually. Rainfall variability within the area of desert climate exceeds 40 percent, reducing to 20 percent on the moist margins of the semiarid zone, which forms a transition between the true desert to the south and the more humid areas farther north. The Black Sea coast of Turkey receives from 78 inches (2,000 mm) to 101 inches (2,600 mm) per year, although the transition from the windward, watered side of the Pontic range to the leeward, dry side can be very abrupt due to the topography. The Mediterranean climate, which is limited to a narrow coastal strip reaching from Gaza to Istanbul is marked by mild winters with ample rain and long, hot summers when Sahara-like conditions prevail. During the summer solstice, the sun is directly overhead at 23° 30′ at north latitude

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(e.g., at Aswan, Egypt). Annual periods of high sun in combination with clear skies through much of the year allow intense solar radiation with subsequent extreme evapotranspiration demands.

Precipitation results from different processes. Orographic precipitation in the Taurus and Zagros Mountains supplies the flow of the Euphrates and Tigris Rivers, which in turn supply the Mesopotamia region with needed water. The mountainous southern coasts of the Black and Caspian Seas, and eastern coast of the Mediterranean Sea, are experience upslope seasonal precipitation. Although, the Red Sea and Persian Gulf acting as powerful sources of water vapor trigger little precipitation locally due to descending air in the Hadley cell. Because latitudinal position of the interior steppe and deserts of Syria, Iraq, Jordan and Saudi Arabia, are made still drier by the surrounding mountain ranges (Evans et al 2004). Convective precipitation occurs on the Anatolian plateau and the steppes of northern Syria which experience receive small quantities of rain in summer season. Equatorial convectional rains provide the waters of the White Nile. Northward migration of inter-tropical convergence zone (ITCZ) in summer season is affected southern region of the Arabian Peninsula. Frontal precipitation particularly in the wintertime occurs mainly in the Northern region of the Middle East and sometimes extending to the south region depending on the deepening of frontal depression. Frontal systems passage from west to east across the region bringing alternating high and low pressure cells. Frontal systems are propelled eastward by the subtropical jet stream.

Surface winds in the Middle East have distinctive qualities and have received local names famous throughout the region. The cold northern wind blowing from the Anatolian plateau to the southern Turkish shore in the winter is the Poyraz (derived from the Greek: bora, i.e., north); the warm on-shore wind in the same location is known as the meltem. Searing desert winds are infamous: The Egyptian Khamasine, which blows in from the desert, is matched by the Ghibli in Libya and the Simoon in Iran.

The rest of the article is arranged in the following way. Regional climate in the Middle East is discussed (section 2). Dust Storms over the Middle East and its impact is described (section 3). Climate change and future climate over the Middle East are explained (section 4). Climate Change Impacts on Water Resources in Middle East is illustrated (section 5). Circulation systems affect the climate of Middle East is described in detail (section 6). Finally, a summary and conclusion are given (section 7).

2. Regional climate in the Middle East 2.1 Climate of Egypt

Egypt is located in the northern part of Africa; however, it includes the Sinai Peninsula, which is considered part of Southwest Asia (Figure 2). Therefore, Egypt is located in both North Africa and Southwest Asia. Egypt has shorelines on the Mediterranean Sea and the Red Sea. It borders Libya to the west, Sudan to the south, and the Gaza Strip and Israel to the east. Egypt is covering 1,001,449 square kilometers of land. Its longest distance from north to south is 1,024 kilometers, and from east to west is 1,240 kilometers. Egypt's natural boundaries consist of more than 2,900 kilometers of coastline along the Mediterranean Sea, the Gulf of Suez, the Gulf of Aqaba and the Red Sea.

Egypt, the North African country, has a weather that is characteristic of the arid to semiarid regions. Egypt has four seasons, Summer, Winter, Autumn and Spring. The climate of Egypt in the winter season (December–February) is cold, moist and rainy while in the summer season (June–August) the climate is hot, dry and rainless, and clear skies, prevail. The main features in the spring season (March–May) are the desert or Khamasine depressions. These winds usually originate in the low-pressure regions which create over Atlas Mountain and move towards the North African coast. They are always associated with strong, hot and dry winds (140 kilometers per hour) that are often laden with dust and sand, increasing the atmospheric pollution. These erratic winds and sandstorms

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may even persist for numerous days, thus disrupting regular life and damaging crops and properties. The climate in autumn season (September–November) is similar to that in spring as it is another transitional season. Khamasine-like depressions begin to cross Egypt during late September and cause a breakdown of the settled summer regime. On the other hand, the higher humidity in this season favors greater frequency of thunderstorms and heavier precipitation, a fact especially true in November.

The circulation pattern may be determined or powerful influence on weather and climate over Egypt. In winter the polar low pressure system (Iceland low) and subtropical high pressure are affected the weather over Egypt. In summer season the low pressure system (Indian monsoon low) and also subtropical high pressure are prevailing, which act as swim i.e. when Indian monsoon is dominant the subtropical high pressure is go back and vice versa. In Spring and Autumn season the Sudan monsoon low in the south and may be a Mediterranean low pressure in north are invaded. 2.1.1 Characteristics of Temperature

The average annual temperature is warmer in the southern parts of Egypt and so Northern regions like Alexandria and others are much cooler. Sometimes during winter the Nile Valley and the Delta even experiences frost and snow falls. Temperatures average between 27°C (80.6°F) and 32°C (89.6°F) in summer, and up to 43°C (109.4°F) on the Red Sea coast. Temperatures average between 13°C (55.4°F) and 21°C (69.8°F) in winter. The northwest steady wind helps hold down the temperature near the Mediterranean coast. There are major fluctuations in the inland arid regions, particularly during summer when the temperature may vary from 43°C (109.4°F) during the day to 7°C (44.6°F) at night. During the winter time the temperature may range from 18°C (64.4°F) during the day to even 0°C (32°F) at night.

Hasanean (2004) and Hasanean and Abdel Basset (2006) studied the winter and summer temperature variability and its affect by global climatic events like North Atlantic Oscillation, El Nino Southern Oscillation, etc. In wintertime the study of the coefficient of variability (COV) over Egypt indicates that the wintertime temperature for Lower Egypt shows more stability than the wintertime temperature for Upper Egypt. The pattern of increased variability in the Upper Egypt areas contrasted with the decrease of variability in the Lower Egypt areas, and indicates that there can be significant spatial differences in variability across Egyptian regions. The relationship between COV and latitude is highly significant, whereas it is non-significant with longitude and mean temperature. In summer the COV analysis shows that the surface temperature is a stable climate element, where its coefficient of variation (COV) is found to below during summer. Also, we found that the reason for the spatial variations of COV is the effect of the surrounding seas that moderate the temperature variability. The relationship between COV and latitudes is not significant, while with longitudes it is significant.

In general the wintertime and summer temperatures have increased in the last two decades of the 20th century. Decreasing trends are observed mainly over Upper Egypt. These trends are in general agreement with trends in the global mean surface temperature since the late 20 th century. The most probable cause of the recent observed warming is a combination of internally and externally forced natural variability and anthropogenic sources. The wintertime and summer temperatures of the area are characterized by rather cool periods in the 1940s and 1960s. Distinctive inter-decadal variations in the wintertime and summer temperatures are found. Among these variations, fairly regular variations of a quasi-20-year periodicity exist, although its amplitude varies between different cycles. Examination of the cumulative summer temperature over Egypt has revealed support for the notion of extended ‘persistence’ over several years, even though simple year to-year persistence may be evident.

During summer seasons, the Mediterranean area is subject to episodes of air temperature increase, which are usually referred to as “heat waves”. These waves are characterized by a long lasting duration and pronounced intensity of the temperature anomaly. Abdel Basset and Hasanean (2006) investigated the causes of this summer heat waves especially during August 1998. They

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concluded that, the increase of temperature is shown to be due to the increase of the subsidence of: 1) the branch of the local tropical Northern Hemisphere Hadley cell; 2) the branch of the Walker type over the Mediterranean Sea and North Africa; 3) the steady northerly winds between the Asiatic monsoon low and the Azores high pressure. Hasanean (2008) also studied summer heat waves especially during August 1998. In summarizing the results from this study, a schematic picture is proposed of some of the principal mechanisms associated with the extreme warming during August 1998. For low values of zonal index (ZI) the surface temperature is high and vise versa. In the period of extreme warming (August 1998) the trough of Indian monsoon is deepened significantly. On other hand the subtropical high pressure is intensified and highly affects surface temperature over Egypt and in turn supported the area by cold air. During August 1998 the situation is reversed. There is a clear duality between the Indian monsoon low pressure index and subtropical high pressure index. The mid-latitude temperature response to a subtropical Hadley circulation anomaly is dominated by enhanced power in low-frequency planetary waves (Hou, 1998). The increase in temperature in Egypt may be associated with the weakness in Hadley cell circulation. Hadley circulation affects North Atlantic subtropical high pressure and the recent trend is argued in connection with recent global warming. During extreme warming of surface temperature the intensity of Hadley cell circulation can lead to intensify the subtropical jet stream. Extreme warming may be related to the change of location and strength of the subtropical jet stream. The strength of subtropical jet stream is shifted to the northward and weakened during extreme warming.

Robaa and Hasanean (2007) studied the human climate over Egypt. The aims of this study are to examine the temporal and spatial variations of human thermal climate by using the clo index. The results of this study are useful for native people and as a guide to tourists or visitors for understanding human thermal comfort, planning outdoor recreational activities and developing the tourist industry. A latitudinal gradient for clo values during all the months of the year in Egypt are found. It is stronger during daytime compared to nighttime. The daytime of April and May have the maximum value of latitudinal gradient. This is due to the effects of Khamasine depressions that are more common during spring season over Egypt. The winter season is characterized by requirements of cold weather wear in 47% (mainly 64% in February) of the country’s area during daytime, while during nighttime of this season the very cold weather wear prevail and it is required for 100% (mainly in December, January and February) of the country’s area. The tropical weather wear are required for only 29% (mainly 45% in May) of the country during daytime in spring while the nighttime in this season is characterized by requirements of very cold weather wear in 44% (mainly 95% in March) of the country’s area. The summer season is characterized by requirements of tropical weather wear in 72% (mainly 80% in July) of the country during daytime while the nighttime of this season is characterized by requirements of comfortable weather wear in 71% (mainly 91% in August) of the country’s area. The summer weather wear are required for only 36% (mainly 43% in November) of the country during daytime in autumn while the nighttime of this season is characterized by requirements of cold weather wear at 47% (mainly 92% in October) of the country’s area. The climatic impacts thus induce the clo classification during the four seasons in Egypt.2.1.2 Characteristics of rainfall

Egypt does not receive much rainfall except in the winter months (Soliman, 2007). South of Cairo, rainfall averages only around 2 to 5 mm (0.1 to 0.2 in) per year and at intervals of many years. Rainfall decreases in the southern parts of Egypt and some areas even receive no rainfall for years. Sometimes sporadic rainfall occurs and results in flash floods. On a very thin strip of the northern coast the rainfall can be as high as 410 mm (16 in), with most of the rainfall between October and March (Soliman, 2006). The northern coast of Egypt experiences precipitation mainly in winter (December, January, and February), (Hafez and Hasanean, 2000). The dramatic swings in annual precipitation in the northern coast of Egypt affect its residents through flood damage in heavy rain years and water rationing in

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drought years. This region is considered an agricultural promising region in Egypt. Generally, on a longer timescale, years of significantly below-normal precipitation intensify the on-going competition between the agricultural, industrial, and domestic users of the scare water resources at the northern coast. Previous investigations of the seasonal-meantime-scale mechanism, that influence the northern coast of Egypt wintertime precipitation focused on the role of the anticyclonic blocking systems that persist over Europe, El-Fandy (1946), Hafez (1995, 1999a). It is envisioned in these studies that the interaction between the pressure systems over western and eastern Europe can influence the planetary–scale atmospheric circulation and affect the cyclogensis in the Mediterranean. In general, climatic fluctuations that occur on the North Atlantic influence weather and climate over the Mediterranean, Rogers (1997). In winter, rain is generally associated with Mediterranean depressions, but when these depressions are not associated with upper cold troughs, they move quickly with very little precipitation. In the spring and autumn, however, rain is usually associated with small desert lows (Sudan monsoon low) with cold upper lows or troughs.

Egypt's Sinai Peninsula falls within an arid climatic belt that crosses northern Africa and southwestern Asia (Habib et al 2008). Despite its aridity, Sinai is occasionally subjected to heavy rainfall causing flash floods, which are commonly characterized by sharp peak discharges with short durations. Several flash floods were recorded in south Sinai, which resulted in significant infrastructural damages, population displacement and, sometimes, loss of lives. Despite their hazardous effects, flash floods in Sinai, and other parts of southern Egypt, represent a potential resource for non-conventional fresh water sources. In order to mitigate flash flood damages and efficiently harvest the flash-flood highly needed fresh water, it is crucially important to accurately predict the occurrence of flash floods in terms of both timing and magnitude. Several studies have been implemented to develop hydrologic models for predicting flash floods in Sinai. Snow falls on Sinai's mountains and some of the north coastal cities such as Damietta, Baltim, Sidi Barrany, etc. and rarely in Alexandria, frost is also known in mid-Sinai and mid-Egypt (Soliman, 2006).2.1.3 Circulation pattern affect climate of Egypt

The study of the interrelation between wintertime temperature over Egypt and winter atmospheric circulation reveals that negative relationships between the El Nino Southern Oscillation (ENSO) index, North Atlantic Oscillation (NAO) index and East Atlantic and West Russian (EAWR) index with wintertime temperature are found, whereas there is a positive relationship between wintertime temperature over Egypt and winter East Atlantic (EA) index Hasanean and Abdel Basset (2006). The NAO is more dominant in wintertime temperature than ENSO, and is highly significant for many stations over Egypt. A strong relationship between winter EAWR and wintertime temperature is found. Variations in local climate may be responding to changes in the circulation index strength, but may also be due to competing influences from other circulation types. Some of the variability in the correlation between temperature and circulation may be due to different circulation types influencing temperature; whereas zonal circulation usually has a dominant influence on temperature (Slonosky et al., 2001). Spectral analyses of the summer temperature illustrated that the sunspot cycle affects summer temperature over Egypt. Other harmonics may be related to El Nino southern oscillation (ENSO) cycle, quasi-biennial oscillation (QBO) cycle, and solar inertial motion cycle. Each of them contribute approximately 9% to summer temperature in Egypt and so their influence on summer temperatures in the area is not so much (Hasanean and Abdel Basset, 2006). Recent satellite measurements of solar brightness, analyzed by Willson (1997), show an increase from the previous cycle of sunspot activity to the current one, indicating that the Earth receives more energy from the Sun. Willson (1997) indicates that if the current rate of increase of solar irradiance continues until the mid twenty-first century, then the surface temperatures will increase by about 0.5°C (32.9°F). This is small, but not a negligible fraction of the expected greenhouse warming. The relationship between cycle length and Earth temperatures is not well understood. Lower-than normal temperatures

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tend to occur in years when the sunspot cycle is longest. The interaction between summer temperature and atmospheric circulation indices is found for North Tropical Atlantic sea surface temperature and ENSO in the last two decades of the 20th century Hasanean and Abdel Basset (2006).

2.2 Climate of the Arabian Peninsula an overviewLiterature and scientific knowledge concerning the climate of the Arabian Peninsula is limited,

incomplete and scattered. Boer, (1997) introduced an overview to the climate of the Arab Peninsula. The Arabian Peninsula belongs to one of the most hostile places on earth with regard to climatological conditions. Limited amounts of freshwater, in combination with extremely high summer temperatures and high evaporation rates, make the Arabian Peninsula a harsh environment for the people, fauna and vegetation. Of the numerous classifications of the world climates which have been drawn up, two of the most well known are the systems by Koppen and Geiger (1928), and Troll and Paffen (1980). However, both authors classify the Arabian climates in a broad scale, and regional differences are not really considered, as at the time there was probably only a very limited number of weather stations operating. Koppen and Geiger (1928) simply classify the climates of the whole Arabian Peninsula as ‘desert climate’, whereas Troll and Paffen (1980) use different climate classes for the Arabian Peninsula. Brief and sound climatological information on Arabia was provided by Walter and Lieth (1967), Muller (1982) and Moore (1986), and they show that there is a broad climatic spectrum on the Arabian Peninsula, from the snows of the Asir Province in Saudi Arabia to the overpowering humidity of the Arabian Gulf, and from the searing heat of the Rub Al Khali to the monsoon rains of the Qara mountains in Dhofar. Moore (1986) divides the Arabian climates into seven different zones for horticultural purposes: (1) the Red Sea coast; (2) the Asir Mountains, and high elevations in Yemen, and the Akhdar Mountains in Oman; (3) the arid central and north-central regions; (4) the semi-arid northern and north-western elevations; (5) the Arabian Gulf coast and the coast along the Gulf of Oman; (6) the Rub al Khali; and (7) the Qara mountains in Oman. For ecological purposes Walter and Lieth (1967) and Muller (1982) provide a variety of climatological diagrams for Arabia, based on digital data measured by standard meteorological stations. As in other arid parts of the world, high rainfall variability is the norm and the impact of drought severe. Variability affects the amount and distribution of rainfall at different time scales. A typical characteristic of rainfall in the arid zones is its negative skew. This means that the probability of having rainfall below the mean is higher, but compensated for by few high rainfall events (De Pauw, 2002).

The Arabian Peninsula (AP) is located in Southwest Asia and connects Asia with Africa (Figure 3). It is located in the sub-tropical belt between 12°N, 35°N, 30°W and 60°W. The main feature of its climate is arid/semiarid nature (Edgell, 2006). In detail, the climate can be explained in terms of regional air masses. There are four different types of air mass (Figure 4) that influence the weather in the Arabian Peninsula (De Pauw, 2002; Kwarteng et al., 2009; Almazroui et al 2009). Firstly, the polar continental air mass affects the area in the winter time (December – February, occasionally mid- March) and comes from the central of Asia as a result of the domination of the Siberian High. The second air mass is the polar maritime air mass. It reaches the area as a result of western low depression movement through winter season. If it is associated with an upper trough, then rainfall is expected over the North of Saudi, Kuwait and Jordan. The third air mass is the tropical continental air mass which influences the AP during spring and early summer. This air mass is hot and dry causing mainly dry convection. Cloudless skies, low humidity, very high temperatures (often >45°C (113°F)), intensive surface heating, and dust characterize the weather system (Fisher and Membery, 1998). The last air mass is the tropical maritime air mass that comes from North of the Indian Ocean and Arabian Sea during Summer. It affects mainly the Southwest of Saudi Arabia, Yemen and coastal line of Oman bringing hot and humid air (Ghazanfar and Fisher, 1998, Abdullah and Al-Mazroui, 1998). Figure 4 (left) shows the source and direction of these air masses. The mechanism of rainfall production over

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the AP is governed by two major factors; the synoptic systems and the topography of the AP. The influence of the topography on the weather of the AP is considered because there are three different types; coastline, desert and mountains. The mechanism of producing rainfall can be described clearly through the interaction of the topography with seasonal pattern. In winter time, the rainfall is produced from two mechanisms. The First source is the movement of the westerly upper troughs which are associated with surface depressions. These systems bring fronts to the area. The second source is the penetration of the Sudan trough which advects warm and humid air. This system is associated with the Siberian ridge which brings cold and dry air to the area. This mechanism is active over the western region and southwest highlands of Saudi Arabia (see figure 4, middle). In spring time, the rainfall still occurs over the whole area. The north of the Arabian Peninsula is under the influence of North African depressions which produce thunderstorms and rainfall. The thunderstorms reach a peak during this season. The southwest mountains receive rainfall from convective systems that are the result of the strong temperature contrast between land and sea, and mountains and valleys. In the interior of Oman, the Oman convergence zone is active and produces deep convective clouds. In summer, the study area is affected by thermal lows which combine with the Indian monsoon to become one system. It causes dust storms over the Northern part of the area and brings warm and humid air to the southern coast of Yemen and Oman which can produce rainfall in the mountains. Also, southwesterly winds affect the southwest mountains of Saudi Arabia and Yemen producing orographic convective rainfall (see figure 4, right). The intense spring summer solar insolation results in strong thermal low around the Arabian Sea. These eventually merge into a thermal trough from Somalia into Pakistan. Surface winds reverse becoming southwest while upper level flow is easterly to northeasterly. Just as the Himalayas prevent cooler air from descending into India and intensifying the winter monsoon, the Himalayas prevent the relatively cooler air from the north from flowing southward in the summer. Hence the intensity of the Somalian-Pakistani heat trough increases and intensifies the monsoon (Science Plane 2004). In autumn, the southwest monsoon starts to change to northeast monsoon. Occasionally, the shower events occur over north of Oman and Emirates due to the passage of cold northeasterlies over the warm water of the Arabian Gulf (Ghazanfar and Fisher, 1998, Abdullah and Al-Mazroui, 1998).

The Arabian Peninsula is warm. More than 90% of its area has a mean annual temperature of 20°C (68°F) (De Pauw, 2002). A small area (shown in red) has a mean annual temperature exceeding 30°C (86°F). The cooler areas are corresponding with the western Yemen highlands, the Asir mountains, and the sandstone and limestone plateau bordering Jordan. The major factors controlling temperature are elevation and latitude. From south to north there is a clear cooling trend, owing to increased exposure to cold continental air masses in winter. Temperature is strongly seasonal, with the lowest temperatures in the period December-February and the highest in the period June-September. The areas exposed to the Indian monsoon are an exception. These show a noticeable temperature drop in July-August. Temperature seasonality tends to increase from the southeast to the northwest. The variability of temperature between years, in contrast with rainfall variability, is very low. Temperature patterns can also be represented as the distribution of available atmospheric energy, which evaporates water or makes plants grow faster, for example. This representation of temperature as a source of energy for plant growth and biomass production can be done through the concept of accumulated heat units or growing degree days, which sum the daily temperatures above a threshold (e.g., 0°C (32°F)) for a specified period (e.g., one year).

The highest rainfall occurs in the Yemeni highlands and Asir mountains, and to a lesser extent in the mountains of northern Oman. The lowest precipitation is recorded in the low-lying areas of the Rub al Khali, the Najd in the north of the Peninsula, and the northern Red Sea coast (Fisher and Membery (1998; De Pauw, 2002).

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2.2.1 Climate of Saudi Arabia (KSA)KSA is characterized by complex topographical surface and cover vast area (approximately

2,250,000 km2), occupies nearly eighty percent of the Arabian Peninsula. KSA stretches from 15.5°N to 32.5°N in latitude and from 32°E to 55°E in longitude (Figure 5). The country is characterized by distinct climatic regions, due to high spatial and temporal temperature variability. In addition, the temperature distribution of the observed dataset is also characterized by high inter-annual variability Almazroui, et al., (2009). KSA region has received little attention, despite the fact that Mediterranean and adjacent regions have been widely explored during the last few decades (Reiter, 1975; Hoskins and Pedder, 1980; Lee et al, 1988; Trigo et al, 2002). In general, most of the country can be classified as arid land (extreme desert and true desert) and semi-arid (semi-desert) ecosystems (Shmida, 1985).

KSA is one of the driest subcontinents in the world (Schyfsma, 1978) characterized by unpredictable and low-erratic precipitation and high temperatures With the exception of the province of Asir with its towns of Jizan on the western coast and Najran, Saudi Arabia has a desert climate characterized by extreme heat during the day, an abrupt drop in temperature at night, and slight, erratic rainfall. Because of the influence of a subtropical high-pressure system and the many fluctuations in elevation, there is considerable variation in temperature and humidity. Along the coastal regions of the Red Sea and the Persian Gulf, the desert temperature is moderated by the proximity of these large bodies of water. Temperatures seldom rise above 38°C (100.4°F), but the relative humidity is usually more than 85 percent and frequently 100 percent for extended periods. This combination produces a hot mist during the day and a warm fog at night. Prevailing winds are from the north, and, when they blow, coastal areas become bearable in the summer and even pleasant in winter. A southerly wind is accompanied invariably by an increase in temperature and humidity and by a particular kind of storm known in the gulf area as a kauf. In late spring and early summer, a strong northwesterly wind, the shamal, blows; it is particularly severe in eastern Arabia and continues for almost three months. The shamal produces sandstorms and dust storms that can decrease visibility to a few meters. 2.2.1.1 Characteristic of temperature

A uniform climate prevails in Najd, Al Qasim Province, and the great deserts. The average summer temperature is 45°C (113°F), but readings of up to 54°C (129.2°F) are common. The heat becomes intense shortly after sunrise and lasts until sunset, followed by comparatively cool nights. In the winter, the temperature seldom drops below 0°C (32°F), but the almost total absence of humidity and the high wind-chill factor make a bitterly cold atmosphere. In the spring and autumn, temperatures average 29°C (84.2°F). Saudi Arabia is warm with a mean annual temperature of Saudi Arabia is warm with a mean annual temperature of about 20oC (68°F) (De Pauw, 2002). However, temperature is strongly seasonal, with the lowest in winter (December-February), with extreme values below 0°C (32°F) in some nights (occasional frost). During the hottest summer months, the heat becomes intense shortly after sunrise and lasts until sunset with daytime temperatures often exceeding 48°C (118.4°F), followed by comparatively cool nights. In spring and autumn seasons, temperatures are mild, averaging about 24°C (57.2°F). In contrast with rainfall variability, temperature variability between years is very low (http://colleges.ksu.edu.sa/Papers/Papers/Dr.%20Al-Rowaily4.pdf).

Almazroui, et al., (2009) investigated climate change signals in Kingdom of Saudi Arabia (KSA) using surface temperature for the available period (1970-2006) at 26 weather stations. The monthly, seasonal and annual values of temperature have been analyzed at each station in KSA. They found that the climatological distribution of temperature throughout the months of the year reflects the effect of meteorological factors and pressure systems affecting the weather and climate in KSA area. They also found that the strong latitudinal gradient of temperature, with particular increase over the north of KSA in winter and spring, is due to the mid-latitude travelling depressions from west to east that affects the weather during this period. In their study the COV of seasonal and annual temperature time series show that the highest values of COV occur in winter while the lowest values occur in the summer. It is

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found that the COV is a function of latitude in winter where it generally decreases gradually from the northern stations to the southern stations. The COV analysis of the second period (1986-2007) shows the existence of low variability mainly over the northern region of the study area comparing to the analysis of the first period (1970-1985). The most significant finding of the trend analysis for the seasonal and annual values is that all stations have positive trends for the annual and seasonal time scale (Table 1), (see also Qureshi and Khan, 1994). The analysis also illustrates an increase in temperature appears in the years 1987, 1991, 1996 and the period from 1998 to 2006 at most stations, while a clear decrease of temperature is observed in the years 1982-1983, 1992-1993 and 1997. These results show a good deal of agreement with the trends of studies on global. They visualized also the decadal and inter-decadal fluctuations or “persistence” in the behavior of the KSA temperature, using cumulative annual means method. The study of decadal and inter-decadal fluctuations in the temperature behavior show that in most stations the period from 1984 to 2006 is characterized in general by positive trend values. The positive trend started from the mid of 1970s in Dhahran, Riyadh Old, Madinah, Jeddah and Taif. This is in agreement with the global climatic trend. They also studied the abrupt climatic change over KSA. In this study abrupt changes of temperature showed a change towards increasing surface temperature (warming) appears in the years 1986, 1987, 1996, 1998 and 2000 (Table 2a) and a change towards decreasing surface temperature (cooling) appears in the years 1983, 1988, 1994, and 1997 (Table 2b), it is suggested that the cold episodes seem to be related to El Nino events while the warm episodes related to La Niña events. Warming trend is found in daily mean, maximum and minimum temperature at Dhahran meteorological station, Saudi Arabia over a period of 37 years spanning from 1970 to 2006 (Rehman, 2009).2.2.1.2 Characteristics of rainfall

The region of Asir is subject to Indian Ocean monsoons, usually occurring between October and March. An average of 300 millimeters of rainfall occurs during this period, approximately 60 percent of the annual total. Additionally, in Asir and the southern Hijaz condensation caused by the higher mountain slopes contributes to the total rainfall. For the rest of the country, rainfall is low and erratic. The entire year's rainfall may consist of one or two torrential outbursts that flood the wadis and then rapidly disappear into the soil to be trapped above the layers of impervious rock. This is sufficient, however, to sustain forage growth. Although the average rainfall is 100 millimeters per year, whole regions may not experience rainfall for several years. When such droughts occur, as they did in the north in 1957 and 1958, affected areas may become incapable of sustaining either livestock or agriculture. Rainfall analysis of the southwestern region of Saudi Arabia is investigated by Abdullah and Al-Mazroui, (1998). They found that, according to Koppen, the whole area of the country can be classified as having a hot desert climate. The southwestern region is an exception, where a mild steppe climate prevails. In this region, rain is more frequent in winter and spring than in summer and autumn. The effect of topography on temperature and rainfall is very distinct. Thus the southwestern part of Saudi Arabia is characterized by unique climatic and topographic features. It receives more rain than any other part. The distribution of the winter rainfall shows maximum values in the northern part of the plateau (e.g Nimas) and gradually decreases in the lowlands on the eastern and western sides. Also, low-altitude and coastal stations receive small amounts of rainfall. It was possible from the available data to classify the southwestern part of Saudi Arabia into 5 regions according to the altitude above mean sea level and the mean annual rainfall. The probability decreases from 90% for 100 mm to 10% for 600 mm. The rainfal1 distributions for the study area are generally best described by the normal and the gamma distributions. The exponential distribution is unacceptable. The inter-annual variability shows that rainfall distribution over the southwestern region is not uniform. There are many factors affecting its irregularity, such as elevation, topographic configuration and orientation. Rainfall variability in the study area is high; although still lower than variability in other parts of the country

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(Abdullah et al. 1992). Over sixty-three representative stations throughout the southwest region for a 21year period that covering different micro-climate conditions, high variations in regional rainfall estimation occurs in the mountainous areas, while the variance decreases in shadow areas in all seasons. The variation of the rainfall estimation accuracy decreases from winter to autumn (Subyani, 2004).

Alamodi, et al., (2008) studied the rainfall analysis and variability and investigated the relation between atmospheric pressure systems and rainfall prediction over the Kingdom of Saudi Arabia (KSA). The most significant findings from this study of monthly, annual and the horizontal distribution of the seasonal average rainfall of each station of KSA can be summarized as following:1- The maximum annual rainfall (Figure 6) occur over two regions the first is the east of the middle region (Hail, Gassim, Hafr Albaten, Qaisoma, Riyad and Dharan) and the second is the southwest region (Taif, Baha, Khamis Meshet, Abha, and Gizan). The lowest rainfall values occur over the north and northwest areas. The south east area does not contain any meteorological station and it considered a dry area.2- The maximum rainfall in winter (Figure 7a) occurs over the north and middle of the east areas and over the mountain area in the south west region. Generally, the highest values of rainfall over KSA occur in spring season (Figure 7b).3- The summer season (Figure 21a) is the lowest season of rainfall over KSA. Except the south west area the amount of rainfall over the other areas is very weak. 4- In autumn season (Figure 21b) only six stations having average value greater than 10 mm (Hail, Hafr Elbaten, Qaisoma, Makkah, Taif and Gizan). The northwest and the southwest areas may be considered as drier areas in this season.

The results of the analysis of the coefficient of variation (COV) of annual, winter, spring, summer and autumn rainfall can be summarized as following:1- The COV values of summer rainfall are greater than those corresponding of winter, spring, autumn and annual values. 2- Generally, the COV of winter rainfall increases gradually from north to south of KSA. The higher values of COV occur at the south of KSA especially at Albaha, Najran and sharorah stations. While in the middle of KSA the higher values occurs at Yanbo and Alahsa.3- The higher values of COV of the annual rainfall time series appears at the stations Alwajh, Yanbo, Jeddah, Najran and Sharorah, while the lowest values of COV appears at Qaisoma, Albaha and kKhamis meshiat. 4- The higher variability in spring season is observed over the western area of KSA (Tabouk, Alwajh, Madinah, Yanbo, Jeddah and Makkah). The lowest values of COV appear at the mountains stations (Taifh, Elbaha, Bisha, Khamis, Abha). 5- The COV of autumn rainfall varies from area to area, where the higher values observed over the east of the middle area (Dhahran, Alwajh, Alahsq, Riyadh and at the lowest two stations (Najran, Sharorah).

The trend analysis of the annual and seasonal values of rainfall over the stations of KSA were made. Positive trends are observed over 16 stations while negative trends are observed over 10 stations (Turaif, Guriat, Arar, Tabouk, Qaisoma, Alahsa, Albaha, Bisha, Khamis Moshet and Abha) of the annual rainfall time series.

From the analysis of rainfall over KSA and its relationship with the pressure systems affecting the weather of KSA it can divide the periods of rainfall over KSA into two main periods. The first period which is strong one contains the months November, December, January, February, March, April and May. About 80% of the total rainfall over KSA occurs during these months. From the analysis of

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weather charts and observations during the winter season we notice that there are some synoptic features that produce rainfall during their passage over our area, it can be summarized as following;

A- Mediterranean depressions migrating from west to east, in association with upper troughs and active phases of the subtropical jet as well as the polar front jet producing rainfall during their passage over our area. Their potential for producing rain decreases generally from north to south over our area except for mountainous areas where the uplift acts as an exterior factor. Consequently, the distribution of winter rainfall in our area shows maximum values in the northern part of the main plateau and gradually decreases in the lowlands on the eastern and western sides.

B- The combination of the westerly frontal troughs bringing clod air from the north west and warm moist southerly air coming from Ethiopia and Sudan, and so a large amount of cloud develop along the area of convergence. Depending on the intensity of the low level convergence, these clouds can occasionally give continuously rain for more than 24 hours or heavy showers with associated thunderstorm.

C- The weather activity during the spring season (March, April and May) is strong over the eastern part of the Mediterranean where the secondary of the main traveling depressions usually associated with sandstorms that reached and affected on our area. Sometimes these secondary Mediterranean depressions causes heavy rainfall at March when the cold air associated with these depressions meets the moist hot southerly air over our area.

The second period occurs in the summer season and represented by Jun, July and August. From the analysis of weather charts and observations during the summer season there are some synoptic features that produce rainfall during their passage over KSA area; it can be summarized as following.

A- In some cases the ITCZ moves northward reaching 25° north associated with upper trough leads to extensive unstable medium level clouds and rainfall occasionally heavy over the south west of KSA. B- The mountain ranges concentrate over the south western area, it leads to developing the clouds and thunder activities. It made lift of the moist air and formed the clouds on the Lee side and give us rainfall. In general, enhanced vertical motions, resulting from low level lifting of air by orographic barriers, which in turn excite gravity waves (mountain waves), often lead to the formation of clouds and precipitation. The two most important orographic forcing mechanisms are thermal and mechanical in nature. Thermal circulations result from differential heating and cooling which varies with the diurnal insolation on the mountain, while mechanical forcing produces a wave disturbance when stably stratified air is forced to rise over a topographic barrier. The mountain wave structures depend upon the direction and speed of the airflow, the mountain height and width dimensions, as well as on the effective heating/cooling changes that occur during the day.

C- The analysis of convective activity during June -August of the last years and observing the frequency of occurrence of convective cloud at each day of July and August have been made. It is found that the dominant pattern associated with the maximum convective activity is as follows: deep thermal low over our area, the subtropical high extended more to the east, Siberian high oscillated to the south, low pressure south west of KSA, maximum solar heating in our area, while at upper air: The Subtropical high extend south east ward to reach our area, and the existence of a low pressure southeast of KSA, and low trough over the red sea. These conditions besides the effect of mountains and the sea breeze and land breeze circulation are affect rainfall in summer season. As the northerly wind meets the southerly wind, there is a strong convergence which causes strong vertical motion, and the moist air forced upward. This causes water vapor to condense, or be squeezed out, as the air cools and rises, resulting in occurrence of convective clouds and heavy precipitation.

During the autumn months the rainfall over KSA is weak and occurs when the Sudan monsoon low coming from south east appears and affecting the weather of KSA area. Also, during this period our area is affected by the early waves invading the Mediterranean. Sometimes these waves

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(depressions) causes rainfall when the cold air associated with these depressions meets the moist hot southerly air over our area.

A case of cyclone over Saudi Arabia on 5 January 2002 is studied by Chakraborty et al., (2006). This type of winter disturbances associated with heavy precipitation over this region. Most of the wintertime rainfall events are associated with southeastward-propagating Mediterranean disturbances. Formation of a sub-synoptic cyclone over heated land owing to such a disturbance, however, had not yet been detected and analyzed before our current study, although polar lows over high-latitude oceans on the polar side of the frontal region in cold seasons have been well studied (Harley, 1960; Businger and Reed, 1989; Yanase et al, 2002; Fu et al, 2004). A small number of sudden events of extreme adverse weather with heavy rainfall and flood, which has high social impacts, affect the Saudi Arabian region during winter.

Barth and Steinkohl, (2004) investigated winter precipitation in the central coastal lowlands of Saudi Arabia. He are is situated at the Gulf coast in Saudi Arabia north of Jubail Industrial City, (Figure 22). The region is characterized by a Mediterranean climate regime displaying a hot and dry summer season and a cooler winter period with rainfall. The analysis of regional climate data was based on the measurements of three weather stations during three winter periods. For further analysis GMS 5(col) IR and MET5/7 IR satellite images were used in order to locate tracks of cyclones and cloud formations. During the observation period four different types of precipitation occurred: (1) cyclones from the Mediterranean Sea; (2) convection cells; (3) the formation of new cyclonic depressions in front of the Zagros Mountains above Iraq and eastern Iran; (4) currents from equatorial areas in Sudan and Ethiopia. The study demonstrates that apart from the well-known Mediterranean depressions there are at least three more characteristic weather situations, which may provide rain for the Eastern Province of Saudi Arabia.

Shwehdi, (2005) examined thunderstorm days in the period 1985–2003 at different areas of Kingdom of Saudi Arabia (KSA) and specifically those areas where lightning strikes are more frequent. Establishing the annual and seasonal thunderstorm days per year (Td/yr) for Saudi Arabia enables transmission and distribution line engineers to calculate and better design a lightning protection system. Maps of thunder days/year (Td/yr) were constructed on the basis of the database records available on lightning incidence in Saudi Arabia at the Presidency of Meteorology and Environment (PME) (http://www.pme.gov.sa/). Annual thunderstorms are most frequent over the southwestern parts of the country, and generally decrease towards the west and east. Due to its low latitude and less temporal change, the west coast of the Red Sea recorded the lowest Td/yr. A secondary maximum Td/yr is apparent in the southeast to central part of the country. Thunderstorm frequency does not, in general, appear to vary in any consistent way with rainfall. There appears to be no evidence of any widespread temporal trend in thunderstorm frequency. The southern region in general, and especially the cities of Abha, Taif and Al-Baha, has shown greater numbers of thunderstorm days all year round. Similarly, this variation did show higher frequency throughout the year. The development of lightning incidence and the counting of Td/yr, as well as the establishment of annual and seasonal lightning maps of Saudi Arabia, are initiating a new era of producing and archiving thunderstorm maps and data records which serve the PME, the utilities, industry and the public.

2.2.1.3 Climate prediction and change over KSAAlamodi, et al., (2008) studied the prediction of autumn rainfall over the western area and winter

rainfall over the eastern area of the Kingdom of Saudi Arabia. They used the meteorological height (Z), temperature (T), sea surface temperature (SST) and southern oscillation index (SOI) as independent variables (predictors). The forecasting method of rainfall is based on deducing an empirical formula relating autumn rainfall with these metrological variables of the preceding august. Rainfall can be predicted by the equation as follows;

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Rain = 2729.98 + 4.53 * Z(7) - 103.48 * SST (7) + 40.85 * SOI

- 20.10 * T(2) - 20 .26 * SST (5) + 0.85 * Z(9) Where the numbers such as 2, 5, 7, and 9 in equation represent the number of steps that the predictor used in each step. So, the rainfall over the western area of KSA is affected strongly by the position and strengthens of the Siberian and subtropical high pressure and also with the southern oscillation index.

Rehman and El Gebiely, (2008) used wavelets technique to calculate the climate predictability indices of daily average time series of air temperature, surface pressure and precipitation for four coastal regions (viz., Dhahran, Gizan, Jeddah, and Yanbu) spread over east and west coasts of Saudi Arabia. The climate predictability indices of precipitation and wind speed time series were found to be independent of the temperature and pressure. The predictability indices of individual parameters were found to have persistence behavior for entire data set while anti-persistence, in most of the cases, for winter and summer data sets.

Alkolibi, (2002) assessed the possible impact of climatic change on Saudi Arabia's agriculture and water supplies using climatic change scenarios from GCMs (General Circulation Models) and related research. The resulting assessment indicates that an increase in temperature and decrease in precipitation could have a major negative impact on agriculture and water supplies in Saudi Arabia. To find signs of climatic change in Saudi Arabia a preliminary assessment of systematic changes in temperature and precipitation was made, based on the records of four Saudi weather stations. The analysis of this data, which dates back to 1961, shows no discernable signs of climatic change during the study period. Such data is, however, limited both spatially and temporally and cannot provide conclusive evidence to confirm climatic changes projected by GCMs. Nevertheless, in the light of recent climatic conditions and rapid population growth, Saudi decision-makers are urged to adopt a `no regret' policy. Ideally, such a policy would include measures to avoid future environmental or socioeconomic problems that may occur in the event of significant climatic change.

2.2.2 Climate of OmanThe Sultanate of Oman is located in the South Eastern tip of the Arabian Peninsula. Its land

borders with Saudi Arabia and the United Arab Emirates in the West and by the Republic of Yemen in the South (Figure 10). The eastern side of the Sultanate borders on the Gulf of Oman and the Indian Ocean with a coastline of nearly 1,690 kilometres. Oman's territory also includes the tip of the strategically important Musandam Peninsular, which is separated by the United Arab Emirates from the rest of Oman. Oman's geography also encompasses the Island of Masirah, off the eastern coast. Oman has an approximate area of 300,000 sq. km. Northern Oman has a mountain chain with heights up to 3,000 m. The Jebel Al Quara in Dhofar in the South divides the Coastal Plains of Salalah from the interior plains of the Nejd (Al-Zidjali, 1996). The Sultanate of Oman is characterized by hyper-arid (<100 mm rainfall), through the arid (100–250 mm rainfall) and semi-arid (250–500 mm rainfall) environments that are experienced in different parts of the country. Scarce and erratic rainfall and varying temperatures have combined to shape the distribution and abundance of vegetation (Fisher and Membery, 1998). The average yearly rainfall varies from a low of 76.9 mm in the interior region to a high of 181.9 mm in the Dhofar Mountains, with an average of 117.4 mm for the whole country (Kwarteng, et al., 2009). 2.2.2.1 Characteristics of temperature

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With the exception of Dhofar region, which has a light monsoon climate and receives cool winds from the Indian Ocean, the climate of Oman is extremely hot and dry most of the year. Summer begins in mid-April and lasts until October. The highest temperatures are registered in the interior, where readings of more than 50°C (122°F) in the shade are common. On the Al Batinah plain, summer temperatures seldom exceed 46°C (114.8°F), but, because of the low elevation, the humidity may be as high as 90 percent. The mean summer temperature in Muscat is 33°C (91.4°F), but the gharbi (literally, western), a strong wind that blows from the Rub al Khali, can raise temperatures from the towns on the Gulf of Oman by 6°C (42.8°F) to 10°C (50°F). Winter temperatures are mild and pleasant, ranging between 15°C (59°F) and 23°C (73.4°F). 2.2.2.2 Characteristics of rainfall

Kwarteng, et al., 2009 studied analysis of a 27-year rainfall data (1977–2003) in the Sultanate of Oman. To detect the trend in rainfall dataset they used Mann–Kendall statistics. Mann-Kendall statistics show a negative but insignificant rainfall trends for the datasets. They found that the average monthly rainfall distribution shows high variability for the geographic locations (Figure 11). The monthly average data for all the stations indicate that the highest rainfall is recorded in February and March and accounts for 35.9% of the yearly rainfall. The lowest monthly rainfall occurs in November, October, June and May, and these months collectively account for only 18.2% of the yearly rainfall. Northern Oman Mountains experience an average monthly rainfall of 11.8 mm with each month exceeding 3.8 mm. Approximately 53.9% of the rainfall occurs in the period from January to April (seif rain), and summer rain (July–August) accounts for 23.3% of the rainfall. Rainfall patterns in the Batinah Plain and the northeast coast are quite similar. In both locations, the majority of rainfall (90.3% in Batinah Plain and 81.2% in the northeast coast) occurs between November and April (seif rain). Summer rainfall (May–September) is quite low and accounts for 6.8 and 15.1% of the rainfall in the Batinah and northeast coast, respectively. For the interior stations, the highest average monthly rainfalls are recorded between January and April and that account for 64.5% of rainfall. The rest of the months have relatively low average monthly rainfall. In the Salalah Plain, 78.4% of the rainfall is recorded between April and August. Rainfall in the months of November–March is relatively low (13.9%). The majority of rainfall over the Dhofar Mountain ranges (67.4%) occurs only in July and August (khareef rain). Rainfall occurring in November–March is relatively low (7%). Even though the Dhofar Mountains and Salalah Plain are adjacent to one another, the amount and distribution of rainfall vary. Also, they found that average annual rainfall shows a positive relationship with topography as depicted in Figure 12. In general, the higher the elevation, is the greater the average rainfall (see also, Babikir, 1985). The correlation coefficient between elevation and rainfall was 0.86 with data of the highest peak (1950 m above sea level) and 0.69 without data of the highest peak. The highest rainfall, 330 mm, was recorded at Saiq with an elevation of 1950 m above mean sea level. The Dhofar Mountains average 185 mm of rain annually. The lowest rainfall, 76 mm, occurs in the interior region with elevations ranging from 300 to 320 m. These stations are located in dry desert conditions. For stations situated less than 100 m above mean sea level, the average yearly rain ranged between 71 and 133 mm only. This difference in the yearly average rainfall may be attributed to the different rainfall mechanisms.

In northern Oman, the main rainfall season occurs between December and April and that accounts for 57.8–82.9% of the annual rainfall. February and March record the highest rainfall accounting for 35.3 to 42% of the yearly rainfall. The Dhofar Mountains and surrounding areas in southern Oman are dominated by the khareef season in July–August, which produces 44.3 to 67.5% of the rainfall in that area. The number of days of light rainfall (<10 mm per day) is the most dominant and accounts for 66–95% of the rain. Rain in excess of 50 mm per day is rare in Oman (0.4 and 2.9%), but when it does occur can result in serious consequences such as flash flooding, human catastrophes and land degradation. Rainfall records indicate that Muscat and surrounding areas are susceptible to tropical

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cyclones and catastrophic rainfall (>100 mm rainfall per day) approximately every 50 years. Fisher and Membery (1998) and De Pauw, 2002 reported the regular occurrence of fog in the western highlands, the Dhofar region, and the central desert of Oman. The contribution of this ‘occult precipitation’ from fog, mist, low clouds, or dew, to the regional water balance might be doubtful. However, these sources of hidden precipitation can help significantly in creating, at a micro-scale, improved conditions for more productive and diverse plant life, particularly grasslands and woodlands.

Rainfall in Oman is caused by four principal mechanisms (Roberts and Wright, 1993; Ministry of Water Resources, 1995).1- Convective rainstorms that are associated with localizedcells of strong convection can develop any time of the year, but mostly during summer. 2- Cold frontal troughs that are most common from November to April originate from North Atlantic or the Mediterranean Sea and may bring Seif rain to the northern parts of Oman, and possibly to central and southern Oman. Rainfalls in these areas vary depending upon the physiographic location. For example, the average rainfall in Muscat, situated on the coast, is 75 mm whereas the average rainfall in the Al Jabal Al Akhdar, with elevations between 400 and 3000 m above mean sea level is between 250 and 400 mm.3- Tropical cyclones originate from the Arabian Sea and tend to be distributed equally between two main cyclone seasons, May to June and October to November. However, cyclones occasionally occur outside the two periods. In general, the Arabian Coast of Oman is affected by a frequency of one cyclone in every 3 years. These cyclones give rise to intense storms and occur once in every 5 years in Dhofar Governorate and once in 10 years in Muscat. Even though these storms are uncommon, when they occur, they can bring heavy rain to the Arabian Coast of Oman. One of such storms crossed Masirah Island in 1977 when 430.6 mm of rain was recorded in 24 h (Watts, 1978). Note that the average annual rainfall for Masirah Island is only 70 mm. 4- On-shore southwesterly monsoon currents occur from June to September and bring humid conditions to much of Oman accompanied by frequent drizzle, fog, mist and rain (khareef ) in Dhofar coast and bordering mountain areas. Occasionally, the monsoon currents penetrate further inland to produce convective storms (see also Babikir, 1985). During the khareef season, parts of Dhofar region are transformed into lush landscapes of green field and verdant vegetation. The monsoon season in Dhofar region brings 100–400 mm of rainfall.

Even though rainfall in Oman, just like most arid regions, is sparse and irregular, it is able to support the plant ecosystem. However, the spectrum of plant life and seasonality of flowering are more influenced by the amount and distribution of rainfall than variations in temperature (Ghazanfar, 1997).

Fleitmann, et al., 2003 stated that, presently, the area sits at the northern limit of the summer migration of the ITCZ and the associated Indian Ocean monsoon rainfall belt. Annual precipitation in this region is highly seasonal, more than 80% of total annual precipitation (400-500 mm yr-1) falls during the summer monsoon months (July to September) when dense clouds and mists cover the region. The clouds are unable to rise higher than 1500 m because of a temperature inversion created by the convergence between the hot dry northwesterly winds and the low-level southwest monsoon winds. As a result, monsoon precipitation occurs as fine drizzle, seldom exceeding more than 5 mm d-1 (unlike the heavy rains normally associated with strong convectionalmonsoonal rainfall).

Recently, a study of Orographic convection over the Hajar Mountains in northern Oman is studied by Al-Maskari, J., and Gadian, (http://homepages.see.leeds.ac.uk/~lecjsam/POST/Oman_obs/ WSN05_p1.01.pdf). The aim of this study is to present two cases (dry and wet). The Hajar Mountain range is a key factor in inducing a significant amount of rainfall during summer months. These steep mountains have peaks of approximately 10,000 feet, and run parallel to the coast of Gulf of Oman. Convective clouds form over the mountains creating a regular occurrence of showers and thunderstorms over a limited area in northern Oman. The active weather is generally of short duration,

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quite intense and is occasionally accompanied by hail and strong downdrafts. In addition to orographic forcing, the synoptic pattern shows that the advection of moisture and large scale lifting are important factors in determining wet days from dry days. As well as moisture from the adjacent sea, another important source of moisture is a tropical monsoonal flow from the south-western parts of the Arabian Sea. In order to understand this orographic convection, various observational data was collected during June/July 2004. Simultaneously, a meso-scale non-hydrostatic model with a horizontal resolution of 2 km was used to simulate the orographic convection.

2.2.3 Climate of the United Arab EmiratesThe United Arab Emirates (UAE) is located at the Southern tip of the Arabian Gulf (Figure 13). It

has borders with the Arabian Gulf from the north and northwest, Saudi Arabia and Qatar from the west, Sultanate of Oman and Saudi Arabia from the south and Gulf of Oman and Sultanate of Oman from the East. The UAE is located between latitudes 22° and 26.5°North and longitudes 51° and 56.5°East. The total area of the United Arab Emirates is 83,600 km2 including a number of islands with a total area of 5,900 km2. The UAE coast stretches over a shallow marine area, with many islands and coral reefs. The UAE can be divided into 3 major ecological areas: coastal areas, mountainous areas, and desert areas. Over four-fifths of the UAE is classified as desert, especially in the western parts of the country (United Arab Emirates, Ministry of Environment and Water.

The United Arab Emirates has an arid and/or hyperarid climate that is subject to ocean effects due to its proximity to the Arabian Gulf and the Gulf of Oman. The climates of the UAE are similar to those of other areas in Arabia, with low mean precipitation rates, whereas the mean annual temperatures increase along a north–south gradient from Kuwait and Riyadh towards Dibba and Muscat (Boer, 1997). There exist at least four major climatic zones: the coastal zone along the Arabian Gulf and the Gulf of Oman, the mountain area, the gravel plains, and the central and southern sand desert (Boer, 1997). Again, the climate of the UAE is simply called ‘tropical semi desert and desert climate’ in the east, and ‘semi deserts and desert climates’ in the west (Boer, 1997).2.2.3.1 Characteristics of temperature

The UAE lies across the Tropic of Cancer and therefore coincides with the area of the high radiation input with a monthly average of 664.9 to 798.4mWh/Sq.cm during summer months. In addition, the area is semi-permanently dominated by subtropical high pressure cells. The subsiding air results in heating and prolongs the hot weather conditions. This keeps the annual average of temperature high and makes the area as one of the hottest areas of the world. Distinction between the four seasons is not clear. Generally winter is from December to February and may extend to mid March. The wind pattern is generally dominated by southeasterly overnight land-sea breeze circulating at 4 to 8 Kt. A hot, dust-laden wind, the Shamal, blows in the spring and summer-period, from March till August. Sometimes these winds can be very strong, and cause Sandstorms, that can occur throughout the year. However, during the first half of June, fresh northwesterly winds may occasionally develop to relieve the very hot and humid weather conditions. The daily mean temperature ranges between 18.2°C (65°F) to 22.5°C (72.5°F), while the minimum night temperature may reach less than 5°C (41°F) over inland areas. Humidity averages between 50% and 60% in coastal areas, and declines sharply inland where its annual average reaches 45%. Relative humidity is least during the month of May, and increases during winter months. Evaporation rates are typically very high, averaging about 8 mm per day. The daily mean relative humidity may range between 50 and 70%. Temperature ranges increase during this period where daily means of 26 (79°F) - 28.4°C (83.1°F) and extreme maximum of 44°C (111°F) to 47°C (116.6°F) are not uncommon. Temperatures exceed 45°C (113°F) in most days resulting in daily mean of about 32 (89.6°F) to 37°C (98.6°F). Temperature falls down during autumn season (October-November) and ranges between 24°C (75.2°F) and 29°C (84.2°F) In the fall transitional period (Oct-Nov) there is again a slow flow reversal from

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Northwest to Southeast flows. This typically occurs over a period of 30-45 days. (Science Plane 2004; United Arab Emirates, Ministry of Environment and Water. www.icarrd.org/en/icard_doc.../national_ UnitedArabEmirates.doc).

In desert areas, minimum temperatures can approach zero during the winter months, with large temperature fluctuations during the course of a typical winter day. In the southern desert regions, temperatures can climb to 50°C (122°F). Average temperatures also show significant variation across the country as well as over time. The annual average temperature is about 27°C (80.6°F) over the 1970-2001 period. Average monthly temperatures for the UAE over this period show clear trends (see Figure 14b). The range in maximum observed monthly temperatures is highest in the summer months, reaching nearly 6°C (42.8°F) across the UAE. The range in minimum observed monthly temperatures occurs during the winter months, when there is about 11°C (51.8°F) between the minimum temperatures throughout the country (The United Arab Emirates, Initial National Communication to the United Nations Framework Convention on Climate Change, Ministry of Energy, http://unfccc.int/resource/docs/natc/arenc1.pdf). Annual differences in temperatures and humidities are relatively small along the coastal areas when compared with areas further inland (Boer 1997).2.2.3.2 Characteristics of rainfall

Over 80% of the annual rainfall occurs during winter (from December to February). Rain is rare and occurs as a result of the afternoon thunderstorm over the eastern high lands or due to isolated thunderstorm accompanying the rarely occurring sea breeze fronts. On very few occasions the Inter-Tropical Convergence Zone (ITCZ) may move northwards and give some rainfall over the area. The most settled weather conditions with very little rain prevail in autumn (October-November), especially in October. In spring (April-May), rainfall is infrequent and is usually associated with isolated thunderstorms (United Arab Emirates, Ministry of Environment and Water. www.icarrd.org/en/icard_doc.../national_ UnitedArabEmirates.doc). In the summer months the UAE is very dry due to the combined effects of upper-level subsidence and limited sources of upper-level moisture. However, isolated convective cells can come through the region and produce precipitation over the mountains. This convective rainfall in the summer is widely known to local meteorologists but in the past has not been captured in any station data (Science Plane 2004).

A combination of atmospheric depressions and northwesterly winds from the Mediterranean results in much of the rainfall is occurred in the winter months, with February and March being the wettest months of the year. While summer rainfall levels are very low in the coastal areas, they are appreciable in the mountainous and southeastern regions, where annual average rainfall ranges between 140 and 200 mm/year. Average annual rainfall over the period 1970-2001 is about 120 mm per year, with rainfall in the driest years being over 20 times below rainfall levels in the wettest years (see Figure 14a). Average monthly rainfall patterns fluctuate widely throughout the year, with most of the rainfall occurring between January and April when temperatures are lowest. These rainfall levels, while showing a large range across the Emirates in the winter months (especially the month of March), are uniformly very low across the UAE during the summer months between July and October. Most of the country is subject to violent dust storms with rainfall being infrequent and irregular, (The United Arab Emirates, Initial National Communication to the United Nations Framework Convention on Climate Change, Ministry of Energy, http://unfccc.int/resource/docs/natc/arenc1.pdf). More rainfall and lower temperatures occur in the north-east than in the southern and western regions (Boer, 1997). The Jebel Jais mountain cluster in Ras al Khaimah has experienced snow only twice since records began (Nazzal, N., N., 2009).

The wintertime monsoon period accounts for most of the precipitation in the lower elevations of the UAE (Science Plane 2004). In winter months the westerly storm tracks dip far enough south. These are typically troughs and depressions, although occasionally a strong front can move through the region bringing precipitation across the UAE (may be once per year). Often such strong fronts will

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have imbedded convective cells. Topographic forcing enhances precipitation in the mountains. Annual rainfall amounts vary considerably in the UAE, and the last several years have been climatologically dry. In April and May a spring transition period develops with a gradual reversal of the Northeasterly flow to a Southwesterly pattern. By June a strong and complex Southwest monsoon develops. This monsoon and its periodic intense wind storms (the Shamal) is a result of meteorological interactions across Africa to the Tibetan Plateau and are unrivaled in its size anywhere in the world.

2.2.4 Climate of QatarThe State of Qatar is a peninsula located between 24o 27- and 26o 10- N latitude and 50o 45- and 51o

40- E longitude (Figure 15). It is about 180 km long and 85 km wide, covering an area of 11,437 km2. Qatar is surrounded on three sides by the waters of the Arabian Gulf and connected to the south by land to Saudi Arabia. The landscape is generally flat to wavy with some prominent hills. The land elevation ranges between 6m to 103 m above sea level. Rocky hills and sand dunes are mostly found in the southern parts of the country. Saline swampy mud flats are common along the coastal areas (http://www.qatarembassy.net/environment.asp).

The Climate of Qatar is desert climate can be described as subtropical dry, hot desert climate with low annual rainfall, very high temperatures in summer and a big difference between maximum and minimum temperatures, especially in the inland areas. The coastal areas are slightly influenced by the waters of the Red Sea, and have lower maximum, but higher minimum temperatures and a higher moisture percentage in the air (http://www.weatheronline.co.uk/reports/climate/Qatar.htm).2.2.4.1 Characteristics of temperature

The long summer (May through September) is characterized by intense heat and alternating dryness and humidity, with temperatures exceeding 55°C (131°F). Temperatures are moderate from November through May, although winter temperatures may fall to 17°C (63°F), which is relatively cool for the latitude. Daily maximum temperatures can reach easily 40°C (104°F) or more. Winter is cooler with occasional rainfall. Spring and autumn are warm, mostly dry and pleasant, with maximum temperatures between 25°C (77°F) and 35°C (95°F) and cooler night Temperatures between 15°C (59°F) and 22°C (72°F). A hot, dust-laden wind, the Shamal, blows in the spring and summer-period, from March till August. Sometimes these winds can be very strong, and cause Sandstorms, that can occur throughout the year, although they are most common in the spring.2.2.4.2 Characteristics of rainfall

Rainfall is negligible, averaging 100 millimeters per year, confined to the winter months, and falling in brief, sometimes heavy storms that often flood the small ravines and the usually dry wadis. The scarcity of rainfall and the limited underground water, most of which has such a high mineral content that it is unsuitable for drinking or irrigation restricted the population and the extent of agricultural and industrial (http://www.weatheronline.co.uk/reports/climate/Qatar.htm). Untermeyer and Al Mahmoud (2005) conclude that the climate of Qatar is varied in the temperature, rain, relative humidity and the atmospheric pressure from one month to another during the seasons of the year. Temperature starts to decrease from October, which is the month of the rainfall and amount of rain increases in winter (December, January). Relative humidity increases in rainfall season (winter), humidity decreases in the summer and it increases in coastal areas more than the inner areas. The atmospheric pressure is related to temperature and the relationship between them is contrary, whenever the temperature increases the atmospheric pressure decreases and vice versa.

2.2.5 Climate of Bahrain Bahrain Islands (latitudes 25° 32' N and 26° 26' N and longitudes 50° 20' E and 50° 50' E), with an

approximate area of 700 square km and comprising an archipelago of 33 islands, are located entirely within the arid and semi-arid zones of the Earth, (Figure 16). The islands are about twenty-four

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kilometers from the east coast of Saudi Arabia and twenty-eight kilometers from Qatar. These regions are found beneath the sinking air at the sub-tropical latitudes of about 30°N and 30°S which produces divergence and drying in the lower troposphere. Consequently, both convective and large-scale condensation processes are suppressed and the regions suffer from insufficient rainfall (Sud et al., 1993). On the other hand, the climate of the Bahrain Islands is influenced by their location on the eastern margins of the deserts and surrounded by the Arabian Gulf waters, which present a departure from the basic distribution of arid zones. By virtue of their proximity to the high pressure cell that develops near 30thN parallel and over the large continental land masses of Western Asia, the Island’s climate is further influenced by a number of continental and maritime air masses. These include Tropical Continental Air Masses (dry) from the north-west, though they originate from the Western Asian desert areas, Tropical Maritime Air Masses (moist) which prevail from the south-east (Indian Ocean and Arabian Sea), and the Polar Continental Air Masses (cold and dry) that prevail from the north-east (Essa, 1989). 2.2.5.1 Characteristics of temperature

Bahrain has two seasons: an extremely hot summer and a relatively mild winter. During the summer months, from April to October, afternoon temperatures average 40°C (104°F) and can reach 48°C (118°F) during June and July. The combination of intense heat and high humidity makes this season uncomfortable. In addition, a hot, dry southwest wind, known locally as the qaws, periodically blows sand clouds across the barren southern end of Bahrain toward Manama in the summer. Temperatures moderate in the winter months, from November to March, when the range is between 10° C (50°F) and 20°C (68°F). However, humidity often rises above 90 percent in the winter. From December to March, prevailing winds from the southeast, known as the “shammal”, bring damp air over the islands. 2.2.5.2 Characteristics of rainfall

Bahrain receives little precipitation. The average annual rainfall is 72 millimeters, usually confined to the winter months. No permanent rivers or streams exist on any of the islands. The winter rains tend to fall in brief, torrential bursts, flooding the shallow wadis that are dry the rest of the year and impeding transportation. However, there are numerous natural springs in the northern part of Bahrain and on adjacent islands. Underground freshwater deposits also extend beneath the Gulf of Bahrain to the Saudi Arabian coast. Despite increasing salinization, the springs remain an important source of drinking water for Bahrain. (http://www.photius.com/countries/bahrain/climate/bahrain_climate_ climate.html).

Elagib and Addin Abdu (1997) studied the climate in the State of Bahrain. They found that the State of Bahrain is ranging between extreme cool-wet and extreme hot-dry episodes. Climatic characteristics of Bahrain generally resemble those of arid and semi-arid zones: rainfall is low, irregular, seasonal and variable, relative humidity is also high, especially during the rainy season, and temperatures are variable but high. Sixty percent of the hot events have been witnessed during the last three decades of 20th century, indicating a warming situation in the country. Moreover, the rainfall pattern has also shifted; some months have become wetter and some drier. Although both the temperature and rainfall vary considerably from one year to another, it is the variability of rainfall in space and time that causes real problems in Bahrain. Variable rainfall and its seasonality result in rainfall ineffectiveness, which leads to deficient water balance. Rainfall in the 1990s has capriciously turned to be higher than normal. The increase in the amount of fall in some cases was as high as 73%.

2.2.6 Climate of Kuwait Kuwait is situated in Southwest Asia, surrounded by the Syrian and Arabian Deserts to the west

and the Persian Gulf to the east (Figure 17). The country of Kuwait is located in a semiarid climate zone. Kuwait has four seasons, Summer, Winter, Autumn and Spring, each explained in detail below:

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The summer months is June, July, August and part of September. These months are mostly dry, hot and dusty. Temperature is exceeding 48°C (118°F), and dust lasting for over a week, all in summer. The seoson "bawarih" starts June 1st and ends July 25th bringing strong winds and heavy dust storms that could last for days, day and night. After the 25 th of July, temperatures reach 50°C (122°F) for a week or two with dry air. The humidity could exceed 90% after mid August and September. Temperatures start to decrease to an average high of 45°C (113°F) by the end of August 43°C (109°F) for the 1st half of September and 40°C (104°F)/ 39°C (102°F) by the end of September (http://mishaal3.tripod.com/uk/id37.html). The Winter months are December, January, February and part of March. During these months Kuwait has a variety of weather patterns. Fog could affect Kuwait during the winter months, the visibility is vanished at times due to the fog. Temperatures could decrease to as low as 0°C (32°F) at night especially at the desert areas where it could be -1.0°C (30°F) for a couple of days. Frosts are slightly rare but are possible in Northern Kuwait. High temperatures range from 10°C (50°F) to 19°C (66°F). The average winter rainfall in Kuwait is 320 mm which is quite alot compared to the other Gulf States. Spring months are part of March, April and May. This season is called the "sarayat" season. It is also a warm season with temperatures in the upper 20°C’s (68°F’s) to the mid 30°C’s (86°F’s). Kuwait has got affected by these thunderstorms in the past. These thunderstorms are associated with strong winds, fierce lightning, heavy rain and hail. They are also associated with dust at times. The Autumn months are October and November. Temperatures start to decrease to the lower 30°C’s (86°F’s) throughout October and the upper 20°C’s (68°F’s) to the mid 20°C’s (68°F’s) in November. Kuwait could have one or two passing thunderstorms by the end of October, however, November is the month where Kuwait wetness pretty heavy thunderstorms associated with hail. The air freshens up after these thunderstorms. Also, it will be cooler.2.2.6.1 Characteristics of temperature

The investigation of temperature data and synoptic maps shows that extremely high temperatures in the warm season are due to the changes in the regional circulation pattern (Nasrallah et al., 2004). Along with typical summer conditions that effect Kuwait and the northern region of the Arabian Gulf, the shift of the Subtropical Jet Stream northward and the buildup of the ridge of high pressure in the 500 hPa level play a major role in heat wave events during the summer season in Kuwait. The hot and dry Arabian Peninsula air masses are transferred to the region and the process is intensified by subsidence of air. The most significant heat wave events, as far as both their duration and intensity are concerned occurred in the last decade of the 20th century. During such episodes the daily maximum temperature significantly exceeded the 1961–1990 average for several days and local temperature extremes were observed. Daily maximum temperatures in Kuwait are strongly affected by the dust and dust storms lasting from several hours to several days (Nasrallah et al., 2004). During these events, the daily maximum temperature can decrease by more than 5°C (41°F) (Al Kulaib, 1984). On average, up to 25% summer days can be affected by dust events (Safar, 1985). Possible changes in the frequency of dust events caused by possible changes in wind characteristics and circulation, and their relationship with the changes in high frequency extreme temperatures should be analyzed.

2.2.6.2 Characteristics of rainfallKuwait lies in an area of marginal, sporadic, and unreliable precipitation; 80% of the rainfall

received in Kuwait falls in the winter months from December through March. A distinct rainy season occurs from November to April, with double peaks in January and March. In addition, the seasonal variability of rainfall is associated with shifts in patterns of mid-latitude storm tracks, which propagate southward toward the Middle East during the winter and spring season Marcella and Eltahir (2008). These trends are characterized using estimates of the spatial correlations of rainfall in Kuwait with the surrounding region. Marcella and Eltahir (2008) found that the basic characteristics and statistics of

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Kuwait’s rainfall are presented. Annual rainfall totals vary from 110 mm (CRU) to 190 mm (GPCP) for the country. In addition, the seasonal cycle of rainfall is beginning in November, peaking in both January and March, and subsiding by April. Moreover, yearly standard deviations range from approximately 40 mm (CRU) to 70 mm (GPCP) while little interdecadal variability is observed. Discrepancies between the CRU, GPCP, and WMO results arise from techniques used in creating both the CRU and GPCP datasets. Finally, the seasonal variability in Kuwaiti rainfall is explained by the north– south migration of the dominant storm track over the region. That is, a positive correlation with rainfall over the eastern Mediterranean in January shifts farther south toward the Red Sea by February before moving north again toward Israel and Plastein and Syria by March. Relationships between Kuwaiti rainfall and SOI indices (or rainfall patterns in Africa and Eurasia) are statistically significant.2.2.6.3 Circulation affect climate of Kuwait

Hot summers, mild winters, and a dry summer precipitation regime characterize the desert of Kuwait (Nasrallah et al 2001). During winter, the North African anticyclone moves westward and the Siberian High generates north-easterly winds across the Arabian Peninsula, bringing mild temperatures. The ocean circulation in the Indian Ocean and Arabian Sea is counterclockwise, pushing warm water up the Arabian Gulf, providing additional moisture for the winter rainfall. While occasional frontal systems from Europe cross the Mediterranean and penetrate the Arabian Peninsula, most lose their moisture before reaching Kuwait. During summer, the inter-tropical convergence zone (ITCZ) migrates north into the Arabian Sea, the Asian anticyclone breaks down, and a strong cyclone develops over northern India. The ocean circulation in the Indian Ocean and Arabian Sea becomes clockwise, pushing warm water toward the west coast of India. The clockwise circulation of the subtropical high over North Africa generates strong westerly winds over the Mediterranean and north-westerly winds over the Arabian Peninsula. North-westerly winds down the Tigris and Euphrates valleys, combined with northerly winds generated by the northern India cyclone, block the Indian monsoon moisture from moving up the Arabian Gulf.

Nasrallah et al., 2001 also, studied teleconnection indices with Kuwait winter precipitation. They found that the September southern oscillation index (SOI) and the October cold tongue index (CTI) are positively correlated with Kuwait winter precipitation. The September West Pacific and November East Pacific teleconnection indices are negatively correlated with Kuwait winter rainfall. A positive SOI, a cold event, for September indicates a strong counter-clockwise circulation in the Arabian Sea as the relative pressure over the Arabian Peninsula becomes much weaker than the Darwin pressure. This sets up a strong winter ocean circulation, which traps warm water in the Arabian Gulf in late summer. Coupled with the increased convection due to the atmospheric low pressure over the region, evaporation and atmospheric moisture are enhanced in the region. The CTI represents the sea surface temperature component of ENSO. A positive CTI in October would indicate a shift from the cold event, which set up during late summer, into a wintertime warm event (El Nino), which brings heavier rainfall to the Middle East. Since the CTI indicator lags the SOI indicator by a month, it indicates a breakdown of the Pacific circulation pattern. Although there is some co-linearity between the SOI and CTI, in the cold season the CTI remains in place regardless of whether the ENSO event is cold or warm. Therefore the CTI and SOI have both overlapping and separate contributions to the Kuwait rainfall variability. It would be very useful to have a complete upper air record for the Middle East to understand the specific relationship between these teleconnection indices and the Kuwait winter precipitation. A negative East Pacific (EP) teleconnection index for November indicates a weak subtropical ridge with split flows around it, where the strong subtropical jet brings moisture and significant rainfall to the south-western United States. The zonal or meridional character of flow around the Northern Hemisphere tends to be fairly consistent across the Western Hemisphere where the oceans and land masses are of similar size. A split flow around a weak subtropical ridge over central Africa would bring warm unstable air into the Kuwait region from the Mediterranean. This

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pattern is highly persistent, though it is generally strongest in October. Years with high winter rainfall in Kuwait are generally characterized by a fairly uniform distribution across all four winter months. A negative West Pacific (WP) teleconnection index for September indicates a meridional flow across Southeast Asia. As this pattern is nearly opposite in phase with the East Pacific (EP) pattern, it appears that a strong meridional pattern in September, which breaks down by November, becoming zonal, brings higher rainfall amounts to the Middle East. This is probably due to some co-linearity between the SOI and the SST indicators, in terms of the ocean circulation. The sea surface temperatures are stronger indicators of ocean circulation, so they account for a larger proportion of the explained variance.

Seas surface temperate is a factor which affect weather and climate of Kuwait (Nasrallah et al., 2001). The Gulf of Oman SST is negatively correlated with Kuwait winter precipitation, while the Gulf of Aden SST is positively correlated with winter rainfall. Based on the standardized regression coefficients, the Gulf of Oman SST produces the greatest influence on Kuwait winter rainfall compared to the other variables. The model shows that a decrease in the September water temperature at the Gulf of Oman, and a corresponding increase of the September water temperature at the Gulf of Aden, brings a wetter winter to Kuwait. The summertime clockwise circulation in the Arabian Sea draws the relatively cold waters of the deep Red Sea out into the Gulf of Aden, while drawing warm water from the shallow Arabian Gulf into the Gulf of Oman. The negative anomaly for Gulf of Oman and corresponding positive anomaly for the Gulf of Aden indicate an early reversal of the currents to the winter pattern. The counterclockwise winter circulation forces the abnormally warm water back into the Arabian Gulf, increasing evaporation and moisture available for winter rainfall.

At the inter-annual time scale, significant correlation is found between the tropical El Niño–Southern Oscillation (ENSO) and annual rainfall anomalies. Similar weak correlations are found between mid-latitude rainfall in Europe and rainfall in Kuwait. The weak connections observed with both tropical and mid-latitude atmospheric systems are consistent with the fact that Kuwait is located in the transitional zone between the tropics and mid-latitudes. The incidence of heat waves, hot days, very hot days and extremely hot days in Kuwait during the warm seasons (May–August) from 1958 to 2000 was examined by Nasrallah et al. (2004). Their results ascertained that the extremely high temperatures in the warm season were caused by the changes in the regional circulation pattern. A comparison of the climatic pattern of the two periods (1962-1998 and 1999-2004) clearly indicates that weather parameters like rainfall, temperature, pan evaporation and wind speed show an increasing trend in Kuwait. Increasing trend in the rainfall pattern in the country is a very positive sign, particularly from the agricultural and environmental point of view.

Temperature is not the only climatic variable likely to change as a result of increase in green house gases. In some regions changes in precipitation, relative humidity, radiation, wind speed and /or potential evapotranspiration may be more marked than for temperature. (http://search.epnet.com/iogin.aspx). In Kuwait, perhaps the increased industrialization based on use of oil and natural gas, production of cement, enhanced emission from vehicles etc. may presumably be the reasons for the possible higher CO2 levels and thus temperature increase. The study of Abdul Salam and Al Mazrooei, (2007) revealed that there is a distinct change in the climatic patterns of Kuwait in the recent years compared to the past. There was an increase in temperature, rainfall, wind speed and pan evaporation during 1999-2004 compared to 1962-1998. The values of relative humidity showed a declining trend. The increasing temperature in the Kuwait environment may be viewed with serious concerns and it is essential to assess the causes of the same and to take possible remedial measures. The positive trend in rainfall pattern is a good sign from environmental and agricultural point of view.

2.2.7 Climate of Yemen

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Yemen is located in the Middle East at the southern tip of the Arabian Peninsula between Oman and Saudi Arabia (Figure 18). It is situated at the entrance to the Bab el Mandeb strait, which links the Red Sea to the Indian Ocean (via the Gulf of Aden) and is one of the most active and strategic shipping lanes in the world. Yemen has an area of 527,970 square kilometers, including the islands of Perim at the southern end of the Red Sea and Socotra at the entrance to the Gulf of Aden. Land Boundaries: Yemen’s land boundaries total 1,746 kilometers. Yemen borders Saudi Arabia to the north (1,458 kilometers) and Oman to the northeast (288 kilometers). Yemen occupies the southern end of the Arabian plateau. The country’s mountainous interior is surrounded by narrow coastal plains to the west, south, and east and by upland desert to the north along the border with Saudi Arabia. The Tihamah is a nearly 419-kilometer-long, semidesert coastal plain that runs along the Red Sea (Library of Congress – Federal Research Division Country Profile: Yemen, August 2008, http://memory.loc.gov/frd/cs/ profiles/Yemen.pdf). Yemen is characterized by five major land systems, as follows; Hot and humid coastal plain, temperate highlands, high plateaus (Hadramawt and Mahra Uplands), desert interior, and islands some of Yemen’s ecological zones are confined to small areas (e.g., islands), with human communities, flora and fauna highly adapted to subsist within them. Other zones are much larger (e.g., Temperate Highlands) and support the majority of the country’s agricultural production. In both cases, climate change poses a major threat (Republic of Yemen, Environment Protection Authority, National Adaptation Program of Action, http://unfccc.int/resource/docs/napa/yem01.pdf). The climate of Yemen generally ranges from semi-humid (at certain areas of the Serrat, as e.g. Bura', Ibb and Taiz) to semi-arid (in the Highlands) until reach to regions that have arid tropical climate (in the Eastern Desert and the Tihama), Herzog, (1998) and http://www.un.org/esa/forests/pdf/ session_documents/unff8/statements/28%20April%20AM/Yemen.pdf). Nevertheless, the climate of Yemen can be classified into eight identifiable regions. These regions are: the Coastal Plains, Low Western Highlands, Medium Western Highlands, High Eastern Highlands, Medium Eastern Highlands, Highlands Plains, Eastern and North Eastern Highlands, Eastern Desert. Typically, the highlands of Yemen have a mid temperate climate and moderately dry in the winter, sometimes the temperature drops below freezing point, and in the summer the climate changes to warm and rainy. The central slopes and the far northern and eastern parts (the Empty Quarter) are generally hot, dry and have harsh desert climate. The coastal plain has a hot climate throughout the year and with high humidity. Table (3) shows the main climatic characteristics of the regions. 2.2.7.1 Characteristics of temperature

Mean annual temperatures range from less than 12ºC (53.6ºF) in the Temperate Highlands (with occasional freezing) to 30ºC (86ºF) in the coastal plains temperatures have increased. The result is occurrence of frequent prolonged hotter droughts during the last three decades interrupted by occurrence of occasional flooding. Drought climate were obvious during the seventies and eighties with low rainfall and record maximum temperatures. The monsoon negatively affects the temperature during the summer time. The absolute maximum is 40° and minimum is 20° but the difference is considerably high between the night and day temperatures. Temperatures are generally very high in Yemen, particularly in the coastal regions. Daily maximum temperatures can reach easily 40°C (104ºF) or more in summer (June to September). Winter is cooler with occasional rainfall. Spring and autumn are warm, mostly dry and pleasant, with maximum temperatures between 25°C (77ºF) and 35°C (95ºF) and cooler night Temperatures between 15°C (59ºF) and 22°C (71.6ºF). The highlands enjoy a temperate, rainy summer with an average high temperature of 21°C (ºF) and a cool, moderately dry winter with temperatures occasionally dipping below 4°C (39.2ºF). The climate of the Tihamah (western coastal plain) is tropical; temperatures occasionally exceed 54°C (129.2ºF), and the humidity ranges from 50 to 70 percent. In Aden the average temperature is 25°C (77ºF) in January and 32°C

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(89.6ºF) in June, but with highs often exceeding 37°C (98.6ºF) (Library of Congress – Federal Research Division Country Profile: Yemen, August 2008 http://memory.loc.gov/frd/cs/profiles/Yemen.pdf). The yearly average of 18.3°C (64.94°F), the absolutely frost free, chilling limit is the lower limit to classify a country as tropical, (Herzog, 1998). This limit is exceeded in all areas below 2000m (-1800), it is massively exceeded in the Tihama with about 30°C (86ºF). The main influence on temperature is exerted by the altitude. Hudeidah is at sea level, Taiz about on 1400m, Sana'a on 2200m. The areas above 3000m form the tropical alpine zones. The typical species is the Juniper (Juniperus excelsa, arab. 'Ar-'ar). All the altitudes above 2000 m might suffer some frost, but only for a few hours during winter nights (until 4am at Sana'a). The minimal temperature in daytime is even for Sana'a in December substantially above zero. In march-april the temperature does not increase, but humidity does so significantly (Herzog, 1998). 2.2.7.2 Characteristics of rainfall

With regards to the rainfall, most of the Yemen areas enjoy two seasons of rainfall, during the months of March/April and July/August. However, the arid tropical climate that prevails in the coastal regions results in erratic precipitation of low amount. The country mean annual rainfall is usually less 200 mm, but the highlands, receive great amount of rainfall usually between 400-800 mm (see also, Library of Congress – Federal Research Division Country Profile: Yemen, August 2008, http://memory.loc.gov/frd/cs/profiles/Yemen.pdf). The Coastal plains and the Eastern Desert Plains get the lowest rainfall rate which is 50-300 mm and 50-100 mm respectively. According to the elevations and wind, the country annual mean temperatures are considerably low. Herzog, (1998) showed that, generally rainfall depends on orography. It is highest at Ibb-Yarim with an estimated 800-1000mm, along the escarpment: Taiz, Jebel Reyma, Jebel Bura', Manakha, Mahwiit; all of them with about 600 (-800) mm per year. Rainfall is decreasing from Manakha to the North and from Taiz to the south, as well from the Serrat to the coast west and south (100mm) and towards the Eastern Desert. Sana'a receives about 170mm, Jebel Lawz (50 km east of Sana'a) 130mm. At Ma'rib it must be already substantially below 100mm a year, not to speak about the Eastern Desert (Ramlat as Sabatain and Rub al Khali). All areas with less than 200 mm do not support forests. Yemen has high rainfall zones at Ibb and Hajja. Rainfall is increasing on the Serrat with increasing altitude. On the leeward side of the mountains it is decreasing the more one moves inland.

Farquharson, et al., (1996) studied the rainfall and runoff in Yemen. In this study they illustrated that the rainfall depends on two main mechanisms, the Red Sea Convergence Zone (RSCZ) and the monsoonal Inter-tropical Convergence Zone (ITCZ). The RSCZ, whose influence is most noticeable in the west of the country, is active from March to May and to some extent in the autumn, while the ITCZ reaches Yemen in July-September, moving north and then south again so that its influence lasts longer in the south. Both the RSCZ and the ITCZ produce precipitation in convective storms of high intensity and limited duration and extent, but the ITCZ storms have a larger areal extent than those of the RSCZ. The relative importance of the RSCZ and the ITCZ in different parts of the country is reflected in the seasonal rainfall distribution, which is summarized in a later section. The annual rainfall distribution shows a combination of the rainfall mechanisms and the orographic influence of the mountain ranges. The relationship between mean annual rainfall and topography is clearly evident(see also, Republic of Yemen, Environment Protection Authority, National Adaptation Program of Action http://unfccc.int/resource/docs/napa/yem01.pdf).

Also, they found that rainfall rises from less than 50 mm along the Red Sea coast to a maximum of 700-800 mm to the west of the main watershed west of Sana'a, and falls steadily to below 50 mm along the Gulf of Aden and also inland (see also, Republic of Yemen, Environment Protection Authority, National Adaptation Program of Action http://unfccc.int/resource/docs/napa/yem01.pdf). The seasonal rainfall distribution is illustrated by monthly averages for typical stations, given in Table 4 and in Figure 19. All the averages are to some extent bimodal but the relative importance of the main rainfall-

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producing mechanisms is illustrated by this distribution. The RSCZ in the early season is more important in the west nearer the Red Sea coast, and also in the north of the country where the effect of the ITCZ loses its impact. 2.2.7.3 Characteristics of wind

A hot, dust-laden wind, the Shamal, blows in the spring and summer-period, from March till August. Sometimes these winds can be very strong, and cause Sandstorms, that can occur throughout the year, although they are most common in the spring (Herzog, 1998). The major factors influencing winds is the atmospheric circulation. In winter the dominant wind is the NE monsoon, in summer the SW-monsoon. The winds in the Tihama (in the mountains it depends on the local topography), blow from october to april from SSE, in summer from NNW, especially during summer, when loads of dust is in the air. Dust clouds are blown from the Tihama up to the Highlands, where they even form "clouds" in summer. In the Serrat the dominant factor is the passat, winds that blow according to temperature differences from the mountains to the plains, from the sea to the land, during daytime, the opposite direction during the night. Generally the wind is changing direction in the evening between seven and nine p.m. - as long as there are no clouds (Herzog, 1998). 2.2.7.4 Future Climate Change in Yemen

According to the country’s First National Communications to the UNFCCC, Yemen’s climate is projected to change significantly over the next 50 years (Table 5) (Republic of Yemen, Environment Protection Authority, National Adaptation Programme of Action http://unfccc.int/resource/docs/napa/ yem01.pdf). Temperature across the country is expected to rise between 1.4°C and 2.8°C by 2050. Precipitation and cloud cover patterns are more uncertain – depending on the GCM, rainfall is projected to decrease by about 24% or increase by about 35%. Follow-up regional climatic modeling indicates that rainfall is expected to decrease across the northern regions, leading to increased pressures on the country’s delicate agriculture and water resources sectors. In recent decades, Yemen rainfall patterns have shown increasing extremes. On the one hand, rainfall has decreased considerably leading led to major agricultural losses, losses of animals and water shortages. On the other hand, flooding was clearly observed in 1996 and during the period 2005-2008. Under warmer climate these features are likely to be further aggravated. In addition to the likelihood that rainfall may decrease over much of Yemen, the timing of rainfall, the intensity of individual storms, the delay between falls and the frequency of inter-annual variability may all change. Rainfall changes will be accompanied by changes in the intensity of wind and frequency of high temperatures and changed cloudiness. When projected annual changes in rainfall are combined with changes in potential evaporation, a new pattern of regime for Yemen is likely to exist by 2050.

2.3 Climate of SyriaThe Syrian Arab Republic lies on the eastern coast of the Mediterranean Sea bounded by Turkey to

the north Iraq to the east, Palestine & Jordan from the south and by Lebanon & the Mediterranean sea to the West (Figure 20). The Total area of the Syrian Arab Republic is 185,180 km2. The Syrian desert is suitable for grass growing and it is used as pastures during the years of sufficient rainfall. Climatically, Syria belongs to an arid and semi-arid region characterized by the Mediterranean type of climate, with warm summers and mild winters. The rainy season extends between September and May. Summers are usually dry (Kattan, 1997). The report of Ministry of Agriculture And Agrarian Reform (1999) and also Project of Syria's Geography and Climate (2009) concluded the geography Syria as follows; 1- The Coastal Region: it lies between the mountains and the sea. 2- The Mountainous Region: it includes the mountains and hills that run from the north to the south along the Mediterranean.

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3- The Interior Region: it includes the plains of Damascus, Homs, Hama, Aleppo, Al Hassakeh, and Dara’a. It is situated to the east of the mountainous region. 4- The Desert (Badia): it consists of the desert plains situated in the southeastern part of the country along the Jordanian and Iraqi borders.

The climate of the Mediterranean characterized by rainy winters and dry and hot summers prevails in Syria. The two seasons are separated by two short transitional seasons. From the climatic point of view, Syria may be divided into four regions according to the rainfall which is affected by the Syrian mountainous ranges and the Western Lebanese mountains. The coastal area is characterized by heavy rainfall in winters and moderate temperature and high relative humidity in summer. The interior area is characterized by rainy winters and hot and dry summers, and the daily big differences between the maximum and minimum temperature. The mountainous area with an altitude of 1000 meters or more is characterized by rainy winters where rainfall may exceed 1000 mm, and a moderate climate in summer. The desert region is characterized by a small amount of rainfall in winter and hot dry summers, (see also Kattan, 1997). Characteristic of the climatic elements can be summarized as follows;2.3.1 Mean temperature:

Regional variations in temperature are comparatively slight, due to the relatively small size of the country (Kattan, 1997). The daily differences between the maximum and the minimum temperatures are generally quite high in most of the country. This difference sometimes reaches 23°C (73.4°F) in the interior region and around 13°C (55.4°F) in the coastal region. The fluctuations in temperature are greater in the interior and desert regions compared with the more moderate areas on the coast or in the mountainous areas of high altitudes (for it is frequently 25°C (77°F)). December and January are the coldest months of the year while July and August are the hottest. In winter the temperature frequently falls under 0°C (32°F) (in all regions except for coastal areas) but rarely under –10oC (14°F) ( North Aleppo and North Hassaka), while in summer it may rise frequently up to 45°C (113°F) (Al Badia and Al Hassaka). Snow falls on mountains with an elevation of 1,500 meters above sea level, while areas located between 800 and 1,500 meters above sea level receive a mixture of rain and snow during the winter season.2.3.2 Maximum temperature:

The average daily maximum temperature was 0.0oC (32°F) - 1.8oC (35.24°F) round its mean in February, May, June, August. It was 0.0oC (32°F) - 1.8oC (35.24°F) below its mean in September, October, November, while it was 0.0C (32°F) - 4.8oC (40.64°F) above its mean in other months .The average monthly maximum temperature of the year was about 23oC (°F) in the coastal district, in the other districts it was 22.5oC (72.5°F) - 28.2oC (82.76°F). The yearly range of maximum temperature (the difference between the highest and lowest average daily maximum temperature) was about 14.0oC (57.2°F) - 16.3oC (61.34°F) in the coastal district, while it was 19.6oC (67.28°F) - 30.2oC (86.36°F) elsewhere. The absolute maximum temperature throughout the country and the year reached 45.4oC (113.72°F) at Alkameshly in July. 2.3.3 Minimum temperature:

The average daily minimum temperature was 0.0oC (32°F) - 2.7oC (36.86°F) round its mean in January, February, May, June, October and 0.1oC (32.18°F) - 1.7oC (35.06°F) below its mean in November, while it was 0.0oC (32°F) - 3.8oC (38.84°F) above its mean in the other months. The average monthly minimum temperature for the year was about 16oC (60.8°F) in the coastal district and in the other districts it was 9.2oC (48.56°F) - 15.0oC (59°F). The yearly range for minimum temperature (the difference between the highest and lowest average daily minimum temperature) was about 16.0oC (60.8°F) in the coastal district while it was 15.1oC (59.18°F) - 23.5oC (74.3°F) elsewhere. The absolute minimum temperature throughout the country and the year dropped to -12oC (10.4°F) at Sarghaia (mountainous station of Western inland district) in February.

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2.3.4 Precipitation: The percentage of the total yearly precipitation to its mean was between 69-101 % in the coastal

district, while it was between 41-73% in step desert district, and it was 55-95% in the western inland. Mountainous coastal district reported the highest yearly total of precipitation which amounted 1660mm in Ein Helqeem and the same station reported the highest monthly total precipitation which amounted 369 mm in February and the same station reported highest daily total precipitation on 4 th of February which amounted 80 mm. During winter, snow falls over all regions with an altitude exceeding 1500 m above the sea level. Regions with an altitude of 800-1500 meters are subject to both rain and snow. Other regions with lower altitude are subject to rain and rarely snow except desert regions where sufficient rain seldom falls. Rain falls continuously or at intervals. Frequently thunderstorms accompanied by heavy showers do occur during winter and the intensity of such showers reaches in some regions 75mm in 24 hours. The mountainous and coastal regions are the regions of heaviest rain. Second in order are the northern region (North Aleppo, Kamishly and Malikieh). Most of these rains are due to depressions accompanied by fronts coming from the Mediterranean. When they meet the mountains they are forced to rise and precipitate as snow and rain over these regions and the interior. The southeastern and the desert regions are the parts with the least amount of rain. From time to time, the country is subject to dry seasons and the rain shortage leads to a great decrease in agricultural production. 2.3.5 Relative Humidity:

Except in the coastal area, the Syrian weather is characterized by high relative humidity during winter and low relative humidity in summer. As for the coastal area, due to the effect of the sea, the contrary is the normal case. It is also observed that the desert and semi desert areas are those with the least relative humidity. During summer, the rate of humidity in the interior region varies from 20% to 50% and in the coastal region it varies from 70% to 80%. In winter it varies from 60% to 80% in the interior region and from 60% to 70% in the coastal region.2.3.6 Pressure and wind:

The average daily station pressure was 0.1 - 4.8 hPa above its mean in March and April and it was 0.0 - 3.6 hPa round its mean during the other months. During winter, the prevailing winds in the eastern part of the country are easterly and in both the northern and northwestern parts are northerly. While other parts of the country are subject to westerly and southwesterly winds. During summer the prevailing winds in the northeastern part of the country are northerly and the remaining parts of the country are subject to westerly and southwesterly winds. Some local winds blow over a number of regions during both summer and winter for limited periods only. Thus northeasterly winds are observed over the north eastern region and south eastern regions. Southeasterly winds blow over the middle of the desert. During summer the coastal region is subject to the sea winds which are westerly in the day time and become easterly at night. Damascus region, in particular, is subject to northwesterly winds that blow continuously every afternoon. During winter, Syria is subject to the influence of the high atmospheric pressure front formed at the center of Siberia and also to the low-pressure front formed in the Mediterranean or approaching from the north east and cause snowfall if they happen to meet the air masses coming from the Mediterranean. The later air masses are largely responsible for the rainfall in winter. In summer, Syria is simultaneously under the influence of the extended low pressure area of the Arab Gulf and the Red sea pressure front, thus dry territorial winds predominate. These winds are very hot when they blow from the Arabian desert or from the western desert in north Africa. There is no rainfall at all during summer.2.3.7 Miscellaneous weather phenomena: 2.3.7a Fog: Not even one case of fog was reported over all parts of the country during the period from June to the end of September. Whereas the total frequency of fog was 0 - 7 days in winter time and it was 0 - 2 days in the other months. The highest monthly frequency of fog reached 7days at Homs

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(western Inland District) in January .And the same station reported highest yearly frequency of fog where it was reached 14 days.2.3.7b Thunderstorm: The total frequency was 0 - 8 days. The coastal district reported 30 - 39 days as annual frequency of thunderstorms. While in the other district reported 0 - 17 days.2.3.7c Rising dust: The total frequency of rising dust was 0 - 8 days from March to August and it was 0 - 2 days In the other months. The step desert reported 19 - 36 days as an annual frequency of rising dust, while it was 0 - 1 day in the other district except Damascus International Airport (Western Inland District) which reported 25 days.

2.4 Climate of LebanonLebanon is located on the Eastern coast of the Mediterranean Sea. It lies between latitude 33° 10'

and 34° 40' N and Longitude 35° 15' to 36° 10' E (Figure 21). The surface area is about 10,452 Square Kilometers (6,495mi), 2/5 of land is mountain and the mean height is about 550 m. The height can be covered by snow from 900 m, till 3086 m. The annual mean of rainfall amount is about 800 mm on the coastal plain, 900 – 1650 mm on mountains, and 225–650 mm on interior plain, Bekaa. 

The climate of Lebanon is typically Mediterranean, humid to sub-humid in the wet season to sub-tropical in the dry season (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf). Lebanon characterized by a long, hot, and dry summer, and cool, rainy winter. In the Lebanon Mountains the gradual increase in altitude produces colder winters with more precipitation and snow. Autumn is a transitional season with a gradual lowering of temperature and little rain; spring occurs when the winter rains cause the vegetation to revive. Topographical variation creates local modifications of the basic climatic pattern. Along the coast, summers are hot and humid, with little or no rain. Heavy dews form, which are beneficial to agriculture. The daily range of temperature is not wide, although temperatures may reach above 38°C (100°F) in the daytime and below 16°C (61°F) at night. A west wind provides relief during the afternoon and evening; at night the wind direction is reversed, blowing from the land out to sea. The summers have a wider daily range of temperatures and less humidity. In the summer, temperatures may rise as high during the daytime as they do along the coast, but they fall far lower at night. 2.4.1 Characteristics of temperature

Mean annual temperature varies on the coast between 19.5°C (67°F) and 21.5°C (71°F). It decreases approximately 3°C for each 500 m elevation. At 1000 m above mean sea level, mean annual temperature is around 15°C (59°F) and becomes 9°C (48°F) at 2000 m above sea level. The lowest temperatures recorded in January vary from 7°C (45°F) at the coast to 0.4°C (33°F) on the mountains. On the contrary, the highest temperatures are obtained in July, where maximum daily temperatures exceed 35°C (95°F) in the Bekaa Valley. The annual average temperatures vary from 15°C (59°F) at the coast to 8°C (46°F) in the mountains and 6°C (43°F) in the Bekaa Valley. Similar temperature values can also obtained at the coast, with less adverse effects due to the relatively high relative humidity. Figure 22 summarizes average annual maximum and minimum temperatures in climatically different locations (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf).2.4.2 Characteristics of rainfall

The wet season coincides with winter period that lasts from November till April (Karam, http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf). Winter is the rainy season, with major precipitation falling after December. Rainfall is generous but is concentrated during only a few days of the rainy season, falling in heavy cloudbursts. The amount of rainfall varies greatly from one year to another. Occasionally, there are frosts during the winter, and about once every fifteen years a light powdering of snow falls as far south as Beirut, in fact, snow covers the highest peaks for much of the year. A hot wind blowing from the Egyptian desert called the khamasine (Arabic for fifty), may provide a warming trend during the autumn, but more often occurs during the spring. Bitterly cold

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winds may come from Europe. Along the coast the proximity to the sea provides a moderating influence on the climate, making the range of temperatures narrower than it is inland, but the temperatures are cooler in the northern parts of the coast where there is also more rain. Both the khamasine and the north winter wind are felt in the Lebanon Mountains. The influence of the Mediterranean Sea is abated by the altitude and, although the precipitation is even higher than it is along the coast, the range of temperatures is wider and the winters are more severe.

While the coastal and mountainous areas are characterized by abundant rainfall distributed over winter season, the Bekaa Valley has a semi-arid to continental climate with unpredictable rainfall and recurrent drought. In the central part the climate is semi-arid, whereas in the northern part it is almost arid to continental, since it is separated from the sea effect by the presence of a high and ridge mountain chain, which height near 3000 m above mean sea level. In the southern Bekaa Valley, a sub-humid Mediterranean climate is dominant, with more reliable rainfall. While at the coast the rain is caused by the accumulation of heavy saturated clouds, or cumulonimbus, the rain received by the mountains is mainly due to the difference in land topography and to the fast variation of climatic and environmental conditions between the sea and the mountains. This is very typical of the northern and central coastal areas, where the high chain of surrounding mountains constitutes a natural barrier to the clouds in the way before reaching the inland. As a result, there is a season of stable rainfall between November and April with average amounts of 800 mm at the coast, 1000 mm in the mountains and 400 mm in the Bekaa Valley (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf). Average annual precipitation on the coastal strip ranges between 700 and 1000 mm, with an increase tendency northward. The northern and mid parts of Mount- Lebanon chain form a natural barrier to the transversal movement of the clouds and result in heavy rains, which sometimes exceed 1500 mm, most of them fall as snow. While the western foothills of Mount-Lebanon are climatically Mediterranean, the eastern foothills are less humid, with a sub-Mediterranean climatic condition, in which rain average 600 mm. The maximum amount of rainfall is observed in January, which range from 50 mm in at El Qaâ in the Northern Bekaa Valley, to 150 mm at Ksara in the Central Bekaa Valley. On the mountains, average rain recorded in January varies between 350 mm at Laqlouq in the Northern mountains, to 300 mm at Jezzine in the Central mountains. At the coast it is around 200 mm (Figure 23). Data reported by Aboukhaled and Sarraf (1970) showed high potential evapotranspiration for summer period, where maximum values were observed in July. (Figure 24). This figure shows also for Tal Amara in the Bekaa Valley and for Abdé and Tyr (Sour) on the coast the rain-potential evapotranspiration plotting curve, which indicates the width of the wet area. When potential evapotranspiration exceeds the rain, the dry period gets started with an amplitude depending on the site. Generally, less adverse effects are observed on the coast than in the Bekaa Valley, where advection effect due to wind drift and high vapor pressure deficit in the air are dominant.

The Bekaa Valley and the Anti-Lebanon Mountains are shielded from the influence of the sea by the Lebanon Mountains. The result is considerably less precipitation and humidity and a wider variation in daily and yearly temperatures. The khamasine does not occur in the Bekaa Valley, but the north winter wind is so severe that the inhabitants say it can "break nails." Despite the relatively low altitude of the Bekaa Valley (the highest point of which, near Baalbek, is only 1,100 meters) more snow falls there than at comparable altitudes west of the Lebanon Mountains. Because of their altitudes, the Anti-Lebanon Mountains receive more precipitation than the Bekaa Valley, despite their remoteness from maritime influences. Much of this precipitation appears as snow, and the peaks of the Anti-Lebanon, like those of the Lebanon Mountains, are snow-covered for much of the year. Temperatures are cooler than in the Bekaa Valley.

From the synoptic aspects, in winter, the atmospheric pressure perturbations originating from South Europe cause abundant rainfall at the coast and on the mountains parallel to it (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf). A maximum transect of 50 km crosses the

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country in width, from a subtropical coastal climate, to semi-arid continental in the Bekaa Valley, through middle mountains, typical of the Mediterranean climate. The dry season coincides with summer period, which starts in June till the end of September. During this period, no rain is recorded and a state of high pressure dominates the whole country, with a general tendency toward Northeast. In summer period, the occidental winds coming from Greece humidify the air on the coast and in the mountains and lower slightly the temperatures. The presence of natural districts at the levels of Marjaoun in the South and Dahr el Baidar in the central Mount-Lebanon permit to the occidental winds to reach partly the southern and central parts of the Bekaa valley. Whereas, in the northern Bekaa Valley, the dry and hot winds originating from the Arab Peninsula contribute to an increase of the day/night temperatures and a decrease of the relative humidity of the air, that increases by consequence the vapor pressure deficit of the air. 2.4.3 Circulation pattern affects climate of Lebanon

Touchan et al. (2005) continued their investigations of the relationships between large-scale atmospheric circulation and regional reconstructed May-August precipitation for the eastern Mediterranean region (Turkey, Syria, Lebanon, Cyprus, and Greece). As part of this study, they conducted the first large scale systematic dendroclimatic sampling for this region from different species. The study found no long-term trends during the last few centuries. They also identified large-scale atmospheric circulation influences on regional May-August precipitation. For example, this precipitation season is driven by anomalous below (above) normal pressure at all atmospheric levels and by convection (subsidence) and small pressure gradients at sea level.

2.5 Climate JordanJordan is situated in Southwest Asia, northwest of Saudi Arabia. The territory of Jordan covers

about 91,880 square kilometers (Figure 25). The kingdom of Jordan is bordered on the west by Israel and the Dead Sea, on the north by Syria, on the east by Iraq, and on the south by Saudi Arabia. It is comparable in size to Indiana. Arid hills and mountains make up most of the country. The southern section of the Jordan River flows through the country. The Characteristics of the Jordan region is sub-humid to hyper-arid climate conditions, high spatio-temporal climate variability and low natural water availability (Menzel, et al., 2007). Jordan has a hot, dry climate characterized by long, hot, dry summers and short, cool winters.

2.5.1 Characteristics of temperature

The climate is influenced by Jordan's location between the subtropical aridity of the Arabian desert areas and the subtropical humidity of the eastern Mediterranean area. The country's long summer reaches a peak during August. January is the coldest month, with temperatures from 5°C (41°F) to 10°C (50°F), and August is the hottest month at 20°C (68°F) to 35°C (95°F). Daily temperatures can be very hot, especially in the summer; on some days it can be 40°C (104°F) or more, especially when the Shirocco, a hot, dry southerly wind blows. These winds can sometimes be very strong and can cause Sandstorms. The fairly wide ranges of temperature during a twenty-four-hour period are greatest during the summer months and have a tendency to increase with higher elevation and distance from the Mediterranean seacoast. Daytime temperatures during the summer months frequently exceed 36°C (97°F) and average about 32°C (90°F). In contrast, the winter months—November to April—bring moderately cool and sometimes cold weather, averaging about 13°C (55°F). Except in the rift depression, frost is fairly common during the winter, it may take the form of snow at the higher elevations of the north western highlands. Usually it snows a couple of times in western Amman.

Hasanean (2001) investigated the trends and periodicity of surface air temperature series from eight meteorological stations in the east Mediterranean using different correlation tests. He found a

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significant positive trend at 99% confidence in Malta, Jerusalem and Tripoli, and negative trend at 95% confidence level in Amman. The trends exhibit an increase (decrease) around 2°C (36°F) (1°C (34°F) ) in minimum (maximum) temperature at Amman. Cohen and Stunhill (1996) studied climate change in the Jordan Valley using rainfall, temperature and global irradiance records for three selected stations, namely, Kfar Blum, Degania and Sedom. According to their analysis, the minimum temperature trends are not consistent, but generally showed an increasing trend over most of the months. The increases in minimum temperature were least in early winter. Their results also showed statistically significant decreases in annual mean maximum temperatures. Also they conclude a marked decrease in irradiance and a significant reduction in atmospheric transmissivity in the region. Smadi, (2006) studied observed abrupt changes in minimum and maximum temperatures in Jordan in the 20th century. This study examines changes in annual and seasonal mean (minimum and maximum) temperatures variations in Jordan during the 20th century. The analyses focus on the time series records at the Amman Airport Meteorological station. The occurrence of abrupt changes and trends were examined using cumulative sum charts (CUSUM) and bootstrapping and the Mann-Kendall rank test. Statistically significant abrupt changes and trends have been detected. Major change points in the mean minimum (night-time) and mean maximum (day-time) temperatures occurred in 1957 and 1967, respectively. A minor change point in the annual mean maximum temperature also occurred in 1954, which is essential agreement with the detected change in minimum temperature. The analysis showed a significant warming trend after the years 1957 and 1967 for the minimum and maximum temperatures, respectively. The analysis of maximum temperatures shows a significant warming trend after the year 1967 for the summer season with a rate of temperature increase of 0.038°C (32.07°F) /year. The analysis of minimum temperatures shows a significant warming trend after the year 1957 for all seasons. Temperature and rainfall data from other stations in the country have been considered and showed similar changes.

Freiwana and Kadioglu (2008a) studied the climate variability of Jordan by examining the annual, seasonal and monthly precipitation and extreme temperature time series of 14 meteorological stations. Signals of climate trends such as warming in maximum temperature, more statistically significant warming in minimum temperature, decreasing trends in daily temperature range were detected. In the winter season, no significant trends have been detected in maximum temperature time series. General, but insignificant warming trends are obvious in minimum temperature and a general decrease in the diurnal temperature range is clearly noticed. In spring, autumn and summer seasons, a slight warming is exhibited in maximum temperature, but the minimum temperature reveals a significant apparent warming trend in the majority of the sites, resulting in a decreasing diurnal temperature range. The plot of Mann–Kendall test statistics for some stations shows that an evidence of cooling trend in maximum temperature and an obvious warming in minimum temperature have started in the beginning of 1970s. This matches with the global issues, where the 1990s was the warmest decade in the 20 th century. Another spell of probable climate variability is evident in the last decade of the 20 th century, where a slight decreasing trend in precipitation accompanied with warming trends in maximum temperature and more significantly, warming trends in minimum temperature, and decreasing daily temperature range, are obvious beyond the year 1992. The natural variability of climate could be as large as the actually observed changes. In the case of Jordan, the time series are usually too short to define a definite long-term climatic trend. It might be a good indication to signal the recent climate variability. The statement ‘nights in Jordan are becoming warmer than days are, with accompaniment of slightly decreasing precipitation’ may be an indirect interpretation of the significant trends found in various climatic time series. The temperature is inversely proportional to the elevation, and therefore (Freiwana and Kadioglu, 2008b), Ras Muneef and Shoubak have the coolest days (the annual maximum temperature is less than 20°C (68°F)) and Jordan valley has the hottest days (the annual

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maximum temperature is more than 30°C (86°F)). Lowest minimum temperatures are experienced in the highest lands, mainly at Shoubak and Ras Muneef, while the highest minimum temperatures are recorded in Aqaba and Jordan Valley. CV values of maximum and minimum temperatures are rather small with skew coefficients close to zero, which imply that the maximum and minimum temperature distributions are close to the normal distribution. Some exceptional cases occur in stations with extreme temperatures such as Aqaba for extremely high maximum and minimum, Shoubak and Jordan University for extremely low minimum temperatures (Freiwana and Kadioglu, 2008b).2.5.2 Characteristics of rainfall

About 70 percent of the average rainfall in the country falls between November and March; June through August are often rainless. Rainfall varies from season to season and from year to year. Precipitation is often concentrated in violent storms, causing erosion and local flooding, especially in the winter months. Figure 13 (Menzel, et al., 2007), showed that mean monthly precipitation pattern in winter. The figure illustrate that over a distance of few more than 300 km precipitation decreases from nearly 1000 mm/a to practically zero. A similar gradient can be found from the west (Mediterranean coastline) to the east (Jordanian plateau). Atmospheric pressures during the summer months are relatively uniform, whereas the winter months bring a succession of marked low pressure areas and accompanying cold fronts. These cyclonic disturbances generally move eastward from over the Mediterranean Sea several times a month and result in sporadic precipitation.

In the part of study of Freiwana and Kadioglu (2008a) statistically insignificant decreasing precipitation trends were detected. In the winter season, no significant trends have been detected in precipitation time series. The general trend in spring and autumn precipitation time series is decreasing, but it is significant in few sites such as QAIA, Shoubak and Wadi Duleil stations. A spell of probable climate variability is evident in the last decade of the 20 th century, where a slight decreasing trend in precipitation accompanied with warming trends in maximum temperature and more significantly, warming trends in minimum temperature, and decreasing daily temperature range, are obvious beyond the year 1992. Also, Freiwana and Kadioglu, (2008b) studied spatial and temporal analysis of climatological data in Jordan. They evaluated climate variability over Jordan by considering temporal and spatial variations on the basis of annual and seasonal meteorological variables including precipitation, relative humidity (RH), maximum and minimum temperatures over 30 years (1971–2000) at 16 representative observation stations over the whole country. The conclusion of this study is as following; 1- The Coefficient of variation (CV) of precipitation varies between 27 and 70%. The lower CV values are dominant in areas, which have more exposure to frontal cyclonic systems passing through the northeastern Mediterranean Sea during winter season causing comparatively stable successive precipitation occurrences. On the other hand, southern and eastern parts of the country are exposed to local instability conditions than synoptic scale precipitation events. In some cases, greater rainfall amounts than the annual average may occur in few hours, or even few minutes, while in other cases no rain or a very little amount of rain may be recorded during few successive years. Yearly and seasonal CV increases toward east and south, which indicates that the aridity increases eastward and southward. 2- The annual and seasonal relative humidity (RH) shows a unique distribution in Jordan, the wettest season as winter and the driest as summer. The yearly RH varies between 47 and 65%. Despite of its location on the northern shores of the Red Sea, Aqaba represents the driest area in the country. The highest RH values are seen in the arid sites such as QAIA and Mafraq, because of their topographic properties related to the major water bodies and the prevailing weather conditions in these areas.

The climate change scenarios expect a reduction of precipitation of about 20–25% in the dry season (April to September) and 10–15% in wintertime with temperature decrease about 1.5°C(35°F) in Jordan during the current half of the century (Ragab and Prudhomme, 2002).2.5.2 Characteristics of wind

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For a month or so before and after the summer dry season, hot, dry air from the desert, drawn by low pressure, produces strong winds from the south or southeast that sometimes reach gale force. Known in the Middle East by various names, including the khamasine, this dry, sirocco-style wind is usually accompanied by great dust clouds. Its onset is heralded by a hazy sky, a falling barometer, and a drop in relative humidity to about 10 percent. Within a few hours there may be a 10°C (50°F) to 15°C (59°F) rise in temperature. These windstorms ordinarily last a day or so, cause much discomfort, and destroy crops by desiccating them. The shamal, another wind of some significance, comes from the north or northwest, generally at intervals between June and September. Remarkably steady during daytime hours but becoming a breeze at night, the shammal may blow for as long as nine days out of ten and then repeat the process. It originates as a dry continental mass of polar air that is warmed as it passes over the Eurasian landmass. The dryness allows intense heating of the earth's surface by the sun, resulting in high daytime temperatures that moderate after sunset (http://en.wikipedia.org/wiki/ Geography_of_jordan).

2.6 Climate of Israel and PalestineIsrael and Palestine are situated between 29.5 and 33.5oN along the southeastern Mediterranean

coast (Figure 27). The country can be divided into 4 longitudinal physiographical strips (from west to east): (1) the Coastal Plain; (2) the hilly regions, including (from north to south) Galilee (highest summit 1208 m), Shomeron (945 m), Jehuda (1020 m) and Negev (1045 m); (3) the Jordan Rift Valley; and (4) the Golan Heights (Goldreich, 1995). The climate over the Middle East, including Israel, is a Mediterranean climate-type (Csa) characterized by a hot, dry summer and short, cool, rainy winters, as modified locally by altitude and latitude (http://www.weatheronline.co.uk/reports/climate/Israel-and-Palestine.htm). The climate is determined by Israel's location between the subtropical aridity characteristic of Egypt and the subtropical humidity of the Levant or eastern Mediterranean. January is the coldest month, with temperatures from 5°C (41°F) to 10°C (50°F), and August is the hottest month at 18°C (64.4°F) C to 38°C (100.4°F). 2.6.1 Characteristics of temperature

Ben-Gai et al., (1999) showed that since the early 1960's the maximum and minimum temperatures over Israel have exhibited a decreasing trend during the cool season, and an opposite, warming trend during the warm season, thus resulting notable increase in the intra-seasonal range. Trend patterns of Maximum and Minimum temperatures over Israel (based on data records from 40 stations) show considerable spatial variability, presumably caused by extensive changes in land use (mesoscale forces) during recent decades (Ben-Gai et al., 1998, 1999). A clearly decreasing trend in the diurnal range is revealed by -0.05°C (31.91°F)/decade and -0.26°C (31.53°F)/decade for the summer and winter, respectively, as well as an appreciable increase of the inter-seasonal range. The nature of the observed trend patterns, with a rather abrupt change from a negative tendency at the end of the cool season, i.e. March, to a positive one at the beginning of the warm season, i.e. April, seem to imply that these changes were most probably imposed by some external factors. A long-term trend of the average seasonal temperatures over the East Mediterranean indicates a warming trend of 0.013oC (32.0234oF)/y (for the period 1948–2002). This warming was combined with an increase in the extremity of the temperature regime, manifested by an increase in the frequency of both “hot” and “cool” days and by an increase in the seasonal maximum temperatures, 0.02oC (32.036oF)/y, which is three times larger than the increase in the respective minimum temperatures. Both trends are demonstrated by the temperature distribution for the two 30-year sub-periods (Saaroni et al., 2003). It is worth noting also that the warm spells have become longer with time.

2.6.2 Characteristics of rainfall

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Extra-tropical cyclones reach Israel mainly during the winter months and less during the transition seasons, with showers along the cold front (and in the cold air mass which follows this front) being the typical precipitation (Gagin and Gabriel, 1987; Goldreich, 1995). Figure 28 from Goldreich, (1995) shows the map of annual rainfall for Israel. Of the annual rainfall, 65% occurs during the 3 month period of December to February. During the summer months (June to August), there is no precipitation (the mean is nil!). In this respect, Israel experiences the extreme case of Mediterranean climate. Snow is uncommon; if it occurs it is generally confined to the tops of hills. Jerusalem (800 m) has an annual average of 2 day of snow (Goldreich, 1995). Rainfall is unevenly distributed, decreasing sharply as one moves southward. In the extreme south, rainfall averages less than 100 millimeters annually; in the north, average annual rainfall is 1,128 millimeters. Rainfall varies from season to season and from year to year, particularly in the Negev Desert. The areas of the country most cultivated are those that receive more than 300 millimeters of rainfall annually; about one-third of the country is cultivable.

Annual totals in Palestine are characterized by southward decreases and eastward increases, culminating in the hilly area in central and northern parts. Eastward from there, decreases towards aridity conditions. The isohyets in general run parallel to the coast and curve sharply westward in the Gaza strip (El-Kadi, 2001). Drought conditions and implication are seen in Gaza started earlier in the late 1960s and become most severe in 1980s, which may be attributed to negative SST anomalies found in the Eastern Mediterranean (Turkes, 1996). In Gaza the months from November to February experienced dry conditions from 1960s to early 1990s with intervening few wet years of the 1970s in December and January. October only shows dry conditions in mid 1980s while March and February are characterized by severe dry conditions. Only April shows wet conditions throughout the whole period. Winter experienced continuing drought conditions despite a weak recovery in early 1990s. Autumn was dry in mid 1970 to late 1980s and above average in mid 1960s to early 1970s. Spring was dry all over the period. Annual rainfall shows dry conditions with wet years in early 1990s. So winter, spring and Annual rainfall all have drought conditions to 1990s. The repeated drought in recent years has given impetus to statistical studies of the precursor role of SST in upsetting the balance of continental and marine rainfall (Yang 1996). However, the relationship between SST anomalies and rainfall is not a direct, caused link, but rather both are related to the circulation and specially the wind anomalies (Drosdowsky, 1993). The resulting decline of SST reduced the large-scale convective activity, instability and the supply of heat and moisture to upper level (Hunt and Davies 1997), hence reducing the potentiality of atmospheric mechanism producing rainfall over the Levant and the dryness continues in Gaza.

The average total rainfall over Israel for the entire summer season, i.e. June–September, is less than 1 mm compared with the typical annual amounts of 500–900 mm over the northern half of the country (Katsenelson, 1969). Accordingly, the winter rain regime has been extensively studied (e.g. Alpert and Reisin, 1986; Alpert et al., 1990; Bitan and Saaroni, 1990; Saaroni and Ziv, 2000). Rain episodes, however, are observed over Israel during the summer season at least once a year (Saaroni and Ziv, 2000). The regime of these episodes was discussed as well as the synoptic and thermodynamic background for their occurrence. The discussion differentiates between the entire summer season, i.e. June–September, and the mid-summer period, i.e. July and August. The study of Saaroni and Ziv, (2000) was analyzed the numerous summer rain and drop events observed in Israel during the 1951–1990 period. The observational analysis of 30 sample stations, located primarily throughout the northern half of Israel, for the June–September period yields the following findings: the mid-summer

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months, July and August, are the driest months, with an average of 0.4 rain days and 0.6 drop days per month of short duration, approximately 1 day on average. These 2 months are rather similar in their rain regime, but differ significantly from the months of June and September. The two latter months also differ from each other: June is more similar to July and August, especially in terms of rainfall, while September has more rain than the other 3 summer months, in both the number and duration of episodes. Moreover, the synoptic situations during rain events in June–August are similar to those of the prevailing Persian Gulf trough, whereas the September events are sometimes related to other systems. For the above arguments it is proposed that the summer season in Israel be defined as June–August, or from the second 10-day period of June until the end of August.

Kutiel and Sharon (1981) and Ben-Gai et al. (1993) demonstrated the high variability of rain in Israel by calculating the correlation coefficients of daily rainfall for time series of neighboring stations. Such correlation is meaningless with regard to summer rainfall due to the extremely high locality and irregularity of the rain in this season, and due to the absence of measurable rainfall at most of the stations (Saaroni and Ziv, 2000). The majority of the summer-rainfall occurred over the northern half of Israel. This may be explained by its proximity to the cyclonic influence of the Persian Gulf trough as opposed to the anticyclonic dominance of the subtropical high in the southern part of the country. The above implies that the planetary boundary layer would tend to be deeper in northern Israel providing a better chance for rain formation there. Although a trend indicating a drop in the Israeli summer rains (frequency and quantity) from north to south can be observed, their local nature makes it difficult to identify any dependence on elevation, distance from the sea and posting conditions, as can clearly be seen in the annual rainfall averages (Saaroni and Ziv, 2000). Synoptic analysis has focused on the thermodynamic and dynamic conditions during the rain events in July and August. Permanent subsidence, the key factor in an absence of rain, is also observed during the rain events while several changes in thermodynamic variables have been detected. The most pronounced change is the cooling at the top of the planetary boundary layer without any significant change in the surface temperatures, resulting in an enhancement of lower-level instability. The absence of significant change in the surface temperatures on rain: drop days seem to reflect the dominance of the east Mediterranean sea-surface temperatures (SSTs) during summer over the Levant region, which is continuously subjected to the Etesian winds during this season.

However, several of the rains occurred while an upper inversion was observed (Saaroni and Ziv, 2000). This apparent contradiction can be explained by the following arguments:The summer rain in Israel is of the local type and typically lasts for several minutes only. Upper level data is recorded only twice a day and therefore may not capture the instantaneous local conditions. . The data is recorded at Bet Dagan station, located on the central coastal plain. Dayan and Rodnizki (1999) found that the inversion layer at Bet Dagan does not necessarily indicate its presence in the northern part of Israel, where most of the rain occurred. The inversion layer during rain: drop days is higher and weaker than normal (see Figure 29), implying a weakening in its inhibiting effect upon individual convective clouds which may penetrate the layer. Figure 30 shows a time series of rain and drop days during the years 1951–1997 based on all the available measuring stations in Israel (approximately 300 stations, Israel Meteorological Service, 1967). It shows differences between the 1950s and 1970s, which maintain the 1951–1997 average; the 1960s and 1980s, which were dryer; and the 1990s (up to 1997) which has significantly higher numbers of rain and drop days. This increase in the incidence of rain days during the 1990s may support their proposed climatic trend, although no significant long-term trend has been identified. The indications of this increase in the last decade suggest that further study of long-term changes in summer rain frequency is required in the future.

Saaroni, et al., (2009) studied the Links between the rainfall regime in Israel and location and intensity of Cyprus lows. This study is the first attempt to quantify the relationship between the synoptic conditions and the rain regime in Israel. The results confirm that the Cyprus lows contribute

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the vast majority of the rainfall in the months November– March. The contribution is higher over the inland areas, around 85%, and slightly lower (77%) along the coastal region. The inter-annual variations in the number of Cyprus lows explain over 50% of the variance in the seasonal and the annual rainfall. The temporal change in the seasonal distribution of the regional synoptic types was found effective for reconstructing the seasonal rainfall through multi-regression scheme. The correlation between the ‘predicted’ and the actual rainfall varied between 0.7 along the coastal region and 0.8 in the mountains. The location of the cyclone centre was found crucial for the spatial distribution of the rainfall since it determines the wind direction, and hence the moisture transport. More specifically, the existence of direct onshore wind and a sufficiently long fetch of the airflow over the Mediterranean Sea are crucial for obtaining considerable rainfall. The intensity of the lows was found important for the rainfall yield as well as for its spatial distribution. The deep lows were found more productive in the mountain areas rather than along the coastal region due to the enhanced orographic effect induced by their stronger winds. In spite of the inherent limitation of the synoptic classification used and the absence of direct upper level information, the surface systems were found to be a highly effective tool for reconstructing the rain regime over Israel. Nevertheless, a future complementary study that incorporates upper level feature may upgrade our ability to reconstruct the rainfall regime over the study region. The approach presented here can serve as a tool for climatic prediction, since it enables to directly interpret the occurrences of specific synoptic types to local rain features. This methodology can also be applied on future regional model predictions of sea level pressure in order to interpret the potential change in rainfall distribution and amounts.

Striem, (1981) studied climatic fluctuations in Israel viewed through rainfall regimes. In this study the seasonal (winter) temperature and the (annual) rainfall are well correlated for Israel, and the change in rainfall can be estimated for a given change of temperature (an increase of 100 mm for 1°C decrease). Within the last century the rainfall in Israel has decreased by one fifth, while the winters grew warmer by 1°C, even for meteorologically normalizing periods of 30 years. In general, the decadal temperature fluctuations of Israel parallel those in certain parts of Europe, hence, climatic changes in Europe may form an indicator for the effect in Israel. Going by analogy, during the warmer period, which reigned during the 11th/12th century, in Israel the rainfall may have been, on the average, less by about one quarter of its present level, and thus near drought level. Two possible, though different, views on how climatic fluctuations may express themselves in hydrological regimes are proposed:One view is based on types of annual rainfall: the frequency of occurrence of annual rainfalls is shown to have a multi-modal distribution, whose 4 modes are hypothetically attributed to 4 different Grosswetterlagen, each characterized by a particular type of rainspell synoptics and properties, resulting in an annual rainfall type. The second view has regard for the band-width of the decadal rainfall range and is based on the frequency distribution of a percentage factor expressing a given year's rainfall as a ratio of an accompanying, medium-term, sliding mean. A possible multi-modality of this percentage factor would mean that the mechanism of Grosswetterlagen is still effective in determining the dominant rain spell type, but the underlying climatic changes in, say, temperature shift the actual rainfall amount accordingly.

Whereas station in the upwind region showed an opposite decreasing trend (Goldrieh and Manes 1979), Similar decreasing rainfall in Gaza which is located in the upwind of the Gaza city near the shoreline, where urbanization has no effects in the rainfall of Gaza (El-Kadi, 2001). The increase of rainfall in southern Israel (Bin-Gai, et al. 1994) was related to the increase in land used and to the global change in SST starting in the early 1960s. The increase in Gaza strip was around 20-25% (El-Kadi, 2001). It could be related to decrease rainfall in northern stations, such as the decrease rainfall of Jerusalem reported above by Striem

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(1981). However the study of 700hpa (Kutiel and Kay. 1992) showed that the anomaly flow associated with centre of positive differences in the north and negative in the south is generally easterly over the Mediterranean such anomaly flow does not suggest an increase frequency of cyclonic passage in the westerly, hence drier than normal conditions in Gaza.

Goldreich (1987) differentiated between the contribution of cloud seeding effects and urban-induced changes that possibly influence the rainfall spatial distribution over Israel’s coastal plain for the periods 1950-1980, using regression analysis separately for seeded versus unseeded days. However, cloud seeding is presumed to enhance only rainfall yield during existing rain-days, but not to produce new rain days when rainfall conditions are lacking (Kutiel, 1990) The seeding processes lead to greater spatial variance in rainfall and very localized shower, and one might deduce that the seeding actually cause a negative effect (Goldriech, 1987).

2.6.3 Circulation pattern affect climate of Israel and PalestineIt is clear evidence for the southward shift of the subtropical jet stream over Israel during ENSO

(Alpert and Resin (1986) have already noted a connection between snowfall in Jerusalem and ENSO events. Yakir et al., (1996) found positive correlation between rainfall in Jerusalem and El Nino years. Price et al., 1998 found that since mid 1970s there appears to be a connection between El Nino events and rainfall, stream flow, lake level and perhaps snowfall. These connection are statistical significant. Although a positive correlation exists, the strongest El Nino does not have the largest stream flow anomalies, and vice versa. However, 8 or 9 El Nino winters had above normal rainfall in northern Israel (Alpert et al., 2005). Alpert et al. (2002) have also shown enhanced contributions of daily torrential rainfall in Italy during El-Nino years. It has been also recently shown (Alpert et al., 2006) that winter rainfall in Israel in extreme seasons (since 1880) is in a significant negative correlation with the rainfall index for the preceding summer Indian Monsoon. In summer Ziv et al., (2004) found that strengthening (weakening) of the Asian Monsoon enhances (weakens) both competing dynamic factors over the East Mediterranean, resulting in the annual minimum of inter-diurnal temperature variations (Saaroni et al. 2003).

Kutiel (1991) studied changes in the patterns of the mean monthly sea level pressure over Europe, the Mediterranean and the Middle East between the two normal periods of 1931-1960 and 1951-1980 for grid points 20-60oN, 20-40oE. He related variations of rainfall with variations in pressure patterns. Kutiel and Kay (1992) studied the climatological variations in atmospheric circulation over the eastern Mediterranean. It was argued by them that, between the 1950s and 1980s, there has been a trend indicating a decreased intensity of the subtropical high-pressure belt over the Sahara desert. This is connected to more temperate summer conditions in the eastern Mediterranean and the Levant region due to an associated decrease in air subsidence there. Such a trend might bring about an increase in summer rain and drop days in the Middle East.

Teleconnections associated with changing patterns of temperature and pressure anomalies over Israel during the second half of the 20th century were investigated by Ben-Gai et al., 2001. Relatively high, statistically significant, correlation coefficients of -0.8 and +0.9 were found between the North Atlantic Oscillation (NAO) Index anomalies and smoothed (5 year running mean) cool season temperature and surface pressure anomalies in Israel, respectively. A relatively high positive correlation, (r = 0.8) was also found between the NAO Index anomalies and smoothed geopotential height of the 1000 hPa pressure level, during the cool season at Bet Dagan radiosonde station located

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on the Israel Mediterranean coastal plain. Correlation coefficients between NAO Index anomalies and the higher standard pressure levels, 850 and 700 hPa, decrease gradually and become negative (not statistically significant) for the 500 hPa level.

It is well known that about 50% of the annual rainfall is reached considerably earlier at the coastal plain as compared to the mountain area. This is related to relatively high temperature differences of the land and sea during the beginning of the rainy season. The large supply of heat and moisture enhances the instability caused by the passage of cold fronts during this period. The effect diminishes with the progress of cooling sea surface temperature during winter and the effect of the mountains becomes pronounced (Goldreich and Manes, 1979).

Ziv, et al., (2006) showed that the major factor that modulates the winter rainfall over the northern half of Israel (the southern Levant) is the East Mediterranean (EM) upper trough, which explains over 0.54 of the rainfall variance. The EM trough coexists with a ridge covering Western Europe. The EM trough is linked with three global factors: both subtropical and polar jets, the northern and southern, and the SST over the tropical Western Pacific. Cold and wet winters in the south Levant are associated with warm and dry winters over Western Europe and vice versa. The linkage between the level of the Dead Sea and the rainfall over the Levant, together with the relationship found between the winter conditions over the Levant and WE, leads us to hypothesize that under the present climatic regime, periods in which the Dead Sea level rose indicate reduced ice accumulation over the icebergs in WE and southwest Scandinavia and vice versa. Price et al., 1998 found that a highly significant statistical connection exists between winter SSTs in the central/eastern Pacific (November-April), and integrated rainfall in northern Israel. Also they found that, there is no shift in time when seasonal averages of rainfall and Jordan River stream flow are concerned. Dry sequences in Jerusalem started in 1944-1945 and remained very sever until 1961-1962 with short humid episode 1962-1970 and since then dry sequences continued where the latest was the most severe (Kutiel et al. 1996). This is consistent to those found in Gaza. The dry conditions in Jerusalem since 1970s, mainly in winter, are associated with south easterlies prevailing from the Arabian desert and to weakening of the northern meridional flow which in turn is related to the continuous weakening of the Siberian high in the last 30 years (Kutiel et al. 1996). In addition the center of the Azores anticyclone has a high frequency from 1950 until 1980 in the eastern section of the Atlantic, and the period 1968-1980 is characterized by high values of the annual central pressure of the Azores anticyclone (Sahsamanoglou, 1990) with an increase of northerly continental flow over the Eastern Mediterranean. This cold wind cools the Eastern Mediterranean and negative temperature occurs (Corte-Real et al. 1995) and the cold continental northerly outbreak is responsible for depleting heat storage of the sea (Flamant and Pelan 1996). The pressure gradient between the ridge in the north and the Red sea trough in the south means that the zonal index is negative, causes quite strong easterly wind in the Levant in the period 1982-1988 and the tropospheric thicknesses between 10oN-80oN was 38gpm higher, with a remarkable increase of gradient over the Middle East (Weber, 1990; Makrogiannis et al. 1991; Saaroni et al. 1996). This is consistent with the dryness of the same period in Gaza, where easterly is a dry wind throughout the year. However, the increase trend in precipitation may be an indication of urban effects on precipitation enhancement in the downwind area (Goldreich and Manes 1979; Amanatidius et al. 1993), and the effect of

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intensive urbanization in the downwind of coastal plain (Goldriech, 1987). Wilby (1993) found a consistent upward increasing trend of cyclonic types from 1950 to 1991 in Britain and Northwest Europe which suggest a decrease penetration of cyclones over the Mediterranean basin and hence less rainfall. However, the Eastern Mediterranean climate is subjected to competing influence from Southern Asia, Africa and Siberia (Reddaway and Bigg 1996).

Moreover the weakening of the Siberian high means that fewer depressions ate moving in the Mediterranean in winter. Atmospheric circulation over the Mediterranean has exhibited significant changes during recent years (Makrogiannis et al. 1991; Sahsamanoglou and Makrogiannis 1992), with an increase of atmospheric pressure which began in 1960 over large parts of the Mediterranean, due to northward shift of depression over the Mediterranean area, and a negative surface-500hpa temperature over the southeast of the Mediterranean. In addition there was a delay in the development of the high pressure over Siberia in 1950-1980 (Kutiel 1991). These facts could result in decrease penetration of mid-latitude depressions in the area and more dry period is noticed in Gaza. The dry conditions of 1968-1985 in Greece; of 1980s in Spain and Turkey; the continuing of drought in Jerusalem since 1970s and in Gibralter since the 1960s are in concordance with the drought conditions found in Gaza (El-Kadi, 2001).

2.7 Climate of CyprusCyprus is an island republic located in the Mediterranean Sea. It is the third largest Mediterranean

island and its topography is dominated by two mountain ranges, the Troodos and the Kyrenia, which are separated by the Central Mesaoria Plain that extends the length of the island from east to west (Figure 32). Cyprus has an intense Mediterranean climate with the typical seasonal rhythm strongly marked in respect of temperature, rainfall and weather generally (Meteorological service in Cyprus, http://www.moa.gov.cy/moa/MS/MS.nsf/DMLcyclimate_en/DMLcyclimate_en?opendocument). Hot dry summers from mid-May to mid-September and rainy, rather changeable, winters from November to mid-March are separated by short autumn and spring seasons of rapid change in weather conditions. The central Troodos massif, rising to 1951 metres and, to a less extent, the long narrow Kyrenia mountain range, with peaks of about 1,000 metres, play an important part in the meteorology of Cyprus. The predominantly clear skies and high sunshine amounts give large seasonal and daily differences between temperatures of the sea and the interior of the island which also cause considerable local effects especially near the coasts.

In summer the island is mainly under the influence of a shallow trough of low pressure extending from the great continental depression centred over southwest Asia. It is a season of high temperatures with almost cloudless skies. Rainfall is almost negligible but isolated thunderstorms sometimes occur which give rainfall amounting to less than 5% of the total in the average year. In winter Cyprus is near the track of fairly frequent small depressions which cross the Mediterranean Sea from west to east between the continental anticyclone of Eurasia and the generally low pressure belt of North Africa. These depressions give periods of disturbed weather usually lasting from one to three days and produce most of the annual precipitation, the average fall from December to February being about 60% of the annual total (Stelio Pashiardis, 2008). Characteristic of the climatic elements can be summarized as follows;2.7.1 Air Temperatures

Cyprus has a hot summer and mild winter but this generalization must be modified by consideration of altitude, which lowers temperatures by about 5°C (41°F) per 1,000 meters and of

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marine influences which give cooler summers and warmer winters near most of the coastline and especially on the west coast. The seasonal difference between mid-summer and mid-winter temperatures is quite large at 18°C (64°F) inland and about 14°C (57°F) on the coasts. Differences between day maximum and night minimum temperatures are also quite large especially inland in summer. These differences are in winter 8°C (46°F) to 10°C (50°F) on the lowlands and 5°C (41°F) to 6°C (43°F) on the mountains increasing in summer to 16°C (61°F) on the central plain and 9°C (48°F) to 12°C (54°F) elsewhere. In July and August the mean daily temperature ranges between 29°C (84°F) on the central plain and 22°C (72°F) on the Troodos mountains, while the average maximum temperature for these months ranges between 36°C (97°F) and 27°C (81°F) respectively. In January the mean daily temperature is 10°C (50°F) on the central plain and 3°C (37°F) on the higher parts of Troodos mountains with an average minimum temperature of 5°C (41°F) and 0°C (32°F) respectively. Frosts are rarely severe but are frequent in winter and spring inland and in some years handicap the economically important production of early vegetable crops and main citrus crops.2.7.2 Sea Temperatures

In the open sea temperatures rise to 27°C (81°F) in August and are above 22°C (72°F) during the six months June to November. During each of the three coolest months, January to March, average sea temperature falls only to 16°C (61°F) or 17°C (63°F). Near all coasts in water three or four meters deep temperatures are very similar to those of the open sea and lie within the range 15°C (59°F) to 17°C (63°F) in February and 23°C (73°F) to 28°C (82°F) in August. There is no significant daily change of sea water temperature except on the coast in the very shallow waters of less than one meter depth.2.7.3 Soil TemperaturesSeasonal change in mean soil temperatures is from about 10°C (50°F) in January to 33°C (91°F) in July at 10 centimeters depth and from 14°C (57°F) to 28°C (82°F) at one meter. On the mountains at 1,000 meters above sea level these mean seasonal values are lowered by about 5°C (41°F). Even in the highest areas penetration of frost into the ground is insufficient to cause problems. Absorption of large amounts of solar energy during the day and high radiation losses in clear skies at night cause a wide daily range of soil temperatures in summer. At the soil surface the daily variation on a typical July day in the lowlands is between 15°C (59°F) near dawn to near 6°C (43°F) in middle of the afternoon. At only 5 centimeters depth the variation is reduced to between 24°C (75°F) and 42°C (108°F) and at 50 centimeters depth there is no daily temperature change.2.7.4 Rainfall

The average annual total precipitation increases up the southwestern windward slopes from 450 millimeters to nearly 1,100 millimeters at the top of the central massif. On the leeward slopes amounts decrease steadily northwards and eastwards to between 300 and 350 millimeters in the central plain and the flat southeastern parts of the island. The narrow ridge of the Kyrenia range, stretching 100 miles from west to east along the extreme north of the island, produces a relatively small increase of rainfall to nearly 550 millimeters along its ridge at about 1,000 meters. Rainfall in the warmer months contributes little or nothing to water resources and agriculture. The small amounts which fall are rapidly absorbed by the very dry soil and soon evaporated in high temperatures and low humidity. Autumn and winter rainfall, on which agriculture and water supply generally depend, is somewhat variable. The average rainfall for the year as a whole is about 480 millimeters but it was as low as 182 millimeters in 1972/73 and as high as 759 millimeters in 1968/69, (The average rainfall refers to the island as a whole and covers the period 1951-1980). Statistical analysis of rainfall in Cyprus reveals a decreasing trend of rainfall amounts in the last 30 year.

Snow occurs rarely in the lowlands and on the Kyrenia range but falls frequently every winter on ground above 1,000 meters usually occurring by the first week in December and ending by the middle of April. Although snow cover is not continuous during the coldest months it may lie to considerable

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depths for several weeks especially on the northern slopes of high Troodos. Hail and Thunder. Hail is reported on an average two or three times a year in the lowlands and probably three times as frequently on the mountains, usually, between November and May, in most districts of Cyprus. Months most liable to have hailstorms are December to April but hail occurring rarely in early summer and autumn is more important because of the considerable damage caused locally to fruit crops. Thunder is rare from June to September but at other seasons is heard on the average on four or five days per month from October to January and two or three days per month from February to May.2.7.5 Relative Humidity of the Air

Elevation above mean sea level and distance from the coast also has considerable effects on the relative humidity which to a large extent are a reflection of temperature differences. Humidity may be described as average or slightly low at 65 to 95% during winter days and at night throughout the year. Near midday in summer it is very low with values on the central plain usually a little over 30% and occasionally as low as 15%. Fog is infrequent and usually confined to the early mornings but there are longer periods on the mountains in winter when cloud often envelops the highest peaks. Visibility is generally very good or excellent but on a few days each spring the atmosphere is very hazy with dust brought from the Arabian and African Deserts.2.7.6 Sunshine

All parts of Cyprus enjoy a very sunny climate compared with most countries. In the central plain and eastern lowlands the average number of hours of bright sunshine for the whole year is 75% of the time that the sun is above the horizon. Over the whole summer six months there is an average of 11.5 hours of bright sunshine per day whilst in winter this is reduced only to 5.5 hours in the cloudiest months, December and January. Even on the high mountains the cloudiest winter months have an average of nearly 4 hours bright sunshine per day and in June and July the figure reaches 11 hours.2.7.7 Winds

Over the eastern Mediterranean generally surface winds are mostly westerly or southwesterly in winter and northwesterly or northerly in summer. Usually of light or moderate strength, they rarely reach gale force. Over the island of Cyprus however winds are quite variable in direction with orography and local heating effects playing a large part in determination of local wind direction and strength. Differences of temperature between sea and land which are built up daily in predominant periods of clear skies in summer cause considerable sea and land breezes. Whilst these are most marked near the coasts they regularly penetrate far inland in summer reaching the capital, Nicosia, and often bringing a welcome reduction of temperature and also an increase in humidity. Gales are infrequent over Cyprus but may occur especially on exposed coasts with winter depressions. Small whirlwinds are common in summer appearing mostly near midday as "dust devils" on the hot dry central plain. Very rarely vortices, approaching a diameter of 100 meters or so and with the characteristics of water spouts at sea and of small tornadoes on land, occur in a thundery type of weather. Localized damage caused by these has been reported on a few occasions but in general Cyprus suffers relatively little wind damage.

2.7.8 Trend in precipitation and temperature during 20th centuryDuring the 20th century remarkable variations and trends were observed in the climate of Cyprus,

particularly in the two basic climatic parameters, precipitation and temperature. Similar climatic variations and trends were observed in countries of the eastern Mediterranean and the Middle East, which is an evidence of change in the general circulation of the atmosphere in the area. In Cyprus the precipitation presented a decreasing trend and the temperature presented an increasing trend see also Stelio Pashiardis (2008). The rate of decrease of the average precipitation in Cyprus during the 20 th

century was one millimeter per year. The decrease in precipitation occurred mainly in the second half of the 20th century compared to those in the first half of the century, as a result of the higher frequency

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of occurrence in the number of years of low precipitation and drought. In the last decades the number of years of low precipitation and drought is greater than before and the semi – arid conditions both in Cyprus and in the eastern Mediterranean were deteriorated. Also, the most of the warm years in the 20th century were observed in the last 20 years. The decrease in the amount of precipitation was remarkable. While the average annual precipitation in the first 30-year period of the century was 559 mm, the average precipitation in the last 30-year period was 462 mm, which corresponds to a decrease of 17%, see also Stelio Pashiardis (2008).

On the other hand, temperature in Cyprus during the 20 th century followed a reverse trend than the precipitation, with a rate of increase of 0.01°C per year. In the period 1976-1998 the average rate of increase in temperature was 0.035°C (32.063°F) / year in the towns and 0.015°C (32.027°F) in the rural areas. The urbanization effect plays an important role in the temperature increase in the towns, however, the increase in the temperature in rural areas is indicative of the climate change in Cyprus area in the last decades. In Cyprus, as well as globally, most of the warm years in the 20 th century occurred in the last two decades. The year 1998 was the warmest in Cyprus and globally. In Cyprus during August 1998 we experienced a very severe heat wave. According to the above rate of changes it is expected that by 2030 precipitation will decrease by 10 - 15% and temperature will increase by 1,0°C (34°F) - 1,5°C (35°F) compared to the normal values of the period 1961- 1990.

2.8 Climate of IraqIraq lies between 29°5- to 37°15- N latitudes and 38°45- to 48° 45-E longitude (Figure 33). Iraq is a

country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert. Iraq shares borders with Jordan to the west, Syria to the northwest, Turkey to the north, Iran to the east, and Kuwait and Saudi Arabia to the south. Iraq has a narrow section of coastline. Two major flowing rivers: the Tigris and Euphrates run through the centre of Iraq from north to south. These provide Iraq with agriculturally capable land and contrast with the steppe and desert landscape that covers most of Western Asia The geography of Iraq is diverse and falls into four main regions: the desert (west of the Euphrates River), the island plateau (between the upper Tigris and Euphrates rivers), the northern highlands of Iraqi Kurdistan, and the alluvial plain or el-'Iraq arabi at the head of the Persian Gulf. The mountains in the northeast are an extension of the alpine system that runs eastward from the Balkans through southern Turkey, northern Iraq, Iran, and Afghanistan, eventually reaching the Himalayas. The desert is in the southwest and central provinces along the borders with Saudi Arabia and Jordan and geographically belongs with the Arabian Peninsula (http://en.wikipedia.org/wiki/Geography_of_Iraq). The climate of Iraq is characterized by sub-tropical, continental, arid to semi arid with dry hot summers and cooler winters. 2.8.1 Characteristics of temperature

The average annual temperature is varies from 8.5ºC (47.3ºF) to 49°C (120.2ºF). The summer temperature range is between 16ºC (60.8ºF) – 49ºC (120.2ºF) while the winter temperature range is between 8.5ºC (47.3ºF) - 14ºC (57.2ºF). Mean minimum temperatures in the winter range is from near freezing (just before dawn) in the northern and northeastern foothills and the western desert to 2°C (35.6ºF) - 3°C (37.4ºF) and 4°C (39.2ºF) - 5°C (41ºF) in the alluvial plains of southern Iraq. They rise to a mean maximum of about 15.5°C (59.9ºF) in the western desert and the northeast, and 16.6°C (61.88ºF) in the south. In the summer mean minimum temperatures range from about 22.2°C (71.9ºF) to about 29°C (48.2ºF) and rise to maximums between roughly 37.7°C (99.86ºF) and 43.3°C (109.94ºF). Temperatures sometimes fall below freezing and have fallen as low as -14.4°C (6.08ºF) at Ar Rutbah in the western desert. They are more likely, however, to go over 46°C (114.8ºF) in the summer months, and several stations have records of over 48°C (118.4ºF).

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The analysis of the 200 hPa maps showed that the northward shift of the subtropical jet stream played a big role in pulling hot dry air masses of the Arabian Peninsula and eastern Africa northward toward Kuwait and southern Iraq, and even to the southern border of Turkey (Nasrallah, et al 2004). The unusual movement of the subtropical jet stream to the north of 40oN (north of Greece, Bulgaria, Turkey and over the Black Sea) had a big effect on the lower layers pulling the high pressure ridge northward. The upper-level ridge of high pressure in 500 hPa started to develop over northeast Africa and moved northward to the center of the Arabian Peninsula. The motion of the Arabian Desert hot dry air mass over the northeastern Arabian Peninsula, Kuwait, the northern Arabian Gulf, and southern Iraq resulted in a rise of the surface temperature. The geopotential heights in 850 hPa dropped remarkably during the heat wave and the low pressure deepened. This resulted in an increase of air temperatures over the northern part of the Arabian Gulf, Kuwait, southern Iraq and western Iran. During the heat wave the low pressure in 850 hPa extended to the southern border of Turkey and to the eastern part of the Mediterranean Sea (Nasrallah, et al 2004). The heat wave affected the northern region of the Arabian Gulf and also the Iraqi and Iranian regions southwest of the Zagros Mountains were influenced by the heat wave (Nasrallah, et al 2004).2.8.2 Characteristics of rainfall

Rainfall is low in central and southern of Iraq (100-200mm) but it concentrates in northern of Iraq which reach about 1000mm and falls in November to April (Al-Falahi, 2008). Roughly 90 percent of the annual rainfall occurs between November and April, most of it in the winter months from December through March. The remaining six months, particularly the hottest ones of June, July, and August, are dry. Except in the north and northeast, mean annual rainfall ranges between ten and seventeen centimeters. Data available from stations in the foothills and steppes south and southwest of the mountains suggest mean annual rainfall between 32 and 57 centimeters for that area. Rainfall in the mountains is more abundant and may reach 100 centimeters a year in some places, but the terrain precludes extensive cultivation (http://en.wikipedia.org/wiki/Geography_of_Iraq).

The combination of rain shortage and extreme heat makes much of Iraq a desert. Because of very high rates of evaporation, soil and plants rapidly lose the little moisture obtained from the rain, and vegetation could not survive without extensive irrigation. Some areas, however, although arid do have natural vegetation in contrast to the desert. For example, in the Zagros Mountains in northeastern Iraq there is permanent vegetation, such as oak trees, and date palms are found in the south.2.8.3 Characteristics of thunderstorm

Thunderstorms sometimes accompany the rain, particularly in the spring when, on average 14 days each year in the eastern, while in the west, thunderstorms occur only a third as often. And when thunderstorms do occur, they are frequently evening events (http://www.magazine.noaa.gov/ stories/mag87.htm). During winter and early spring, low visibility is common at night and in the early morning in the Tigris and Euphrates river valleys when fog and stratus clouds prevail. This is intensified by strong thermal highs over Iran and in advance of low-pressure systems out of the Mediterranean. Fortunately, fog and stratus clouds occur mostly at night and towards sunrise and burn off before midday (in most cases) (http://www.magazine.noaa.gov/stories/mag87.htm).

There are two common storm tracks in the area. In the first, storms move through the Mediterranean just south of Turkey and curve northward into the Caspian Sea. Multiple cloud layers (low cloud to cirrus clouds) and precipitation with the low can take from two to four days to transit Iraq. Mediterranean storms that follow the second storm track come out of the sea into Jordan, Syria and Iraq on the way into the Persian Gulf. They exit the area through the Strait of Hormuz and the Gulf of Oman into the Indian Ocean and eventually move toward India. These systems also cause multiple layers of cloud cover 1 to 2 days ahead of and 1 to 2 days behind the system. Most storms pass through in 2 to 3 days, but some stall and take as many as 6 days to move out of the area. The second cause for cloud cover is the subtropical jet stream, which flows across the Arabian Peninsula and brings a band

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of cirrus clouds through the area. Deep low-pressure systems displace the jet south for short periods (http://www.magazine.noaa.gov/stories/mag87.htm).2.8.4 Characteristics of wind

Another climate feature in Iraq is winds. Specifically, the summer months are marked by two kinds of wind phenomena. The southern and southeasterly sharqi, a dry, dusty wind with occasional gusts of eighty kilometers an hour, occurs from April to early June and again from late September through November. It may last for a day at the beginning and end of the season but for several days at other times. This wind is often accompanied by violent dust storms that may rise to heights of several thousand meters and close airports for brief periods. From mid-June to mid-September the prevailing wind, called the shamal, is from the north and northwest. It is a steady wind, absent only occasionally during this period. The very dry air brought by this shamal permits intensive sun heating of the land surface, but the breeze has some cooling effect (http://en.wikipedia.org/wiki/Geography_of_Iraq).

2.9 Climate of TurkeyTurkey is situated in Anatolia and the Balkans, bordering the Black Sea, between Bulgaria and

Georgia, and bordering the Aegean Sea and the Mediterranean Sea, between Greece and Syria (Figure 34). The geographic coordinates of the country lie at 39°N, 35°E. The area of Turkey is 780,580 km2. Although Turkey is situated in large Mediterranean geographical location where climatic conditions are quite temperate, diverse nature of the landscape, and the existence in particular of the mountains that run parallel to the coasts, result in significant differences in climatic conditions from one region to the other. While the coastal areas enjoy milder climates, the inland Anatolian plateau experiences extremes of hot summers and cold winters with limited rainfall.

Turkey has a Mediterranean climate with marked winter rains (Jones, 1995). According to Thornthwaite method; semi dry areas are the inland Anatolia, Iğdır and Şanlıurfa; very wet region is the Eastern Black Sea; humid regions are Black sea and the around of Bitlis and Muğla and the other large areas of Turkey are semi dry and less humid climatic regions (see Figure 35, Sensoy, et al, 2008). Taha et al. (1981) and Martyn, (1992) found that most climate regions in Turkey were characterized by aridity and continentality, and thus they concluded that the influence of the surrounding Mediterranean and Black seas was restricted.2.9.1 Characteristics of temperature

Mean maximum and minimum surface air temperatures recorded at 70 climatic stations in Turkey during the period 1929–1999 were analyzed by Turkes et al. (2002). Their analysis revealed spatial and temporal patterns of long-term trends, change points, significant warming and cooling periods and linear trend rates per decade. It also outlined that annual; winter and spring mean temperatures have increased, notably over the southern regions of Turkey, whereas summer and particularly autumn mean temperatures have reduced over the northern and continental inner regions. Annual, winter, spring and summer maximum temperatures have indicated a positive trend at many stations, except those in the Central Anatolia and Black Sea regions and partly in the Eastern Anatolia region. Minimum temperatures of -30°C (-22°F) to -38°C (-36.4°F) are observed in the mountainous areas in the east, and snow may lie on the ground 120 days of the year. Winters are bitterly cold with frequent, heavy snowfall. Villages in the region remain isolated for several days during winter storms. In Istanbul and around the Sea of Marmara the climate is moderate (winter 4°C (39.2°F) and summer 27°C (80.6°F); in winter however the temperatures can drop below zero. In Western Anatolia, there is a mild Mediterranean climate with average temperatures of 9°C (48.2°F) in winter and 29°C (84.2°F) in summer. On the southern coast of Anatolia the similar climatic condition are observed. The climate of the Anatolian Plateau is a steppe climate. There is a great temperature difference between day and night. Rainfall is low but it usually in form of snow. The average temperature is 23°C (73.4°F) in summer and -2°C (28.4°F) in winter. The climate in the Black Sea area is wet, and humid (summer

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23°C (73.4°F), winter 7°C (44.6°F)). In the Eastern Anatolia region there is a long winter, and snow remains on the ground from November until the end of April (the average temperature in winter is -13°C (55.4°F)) and in summer 17°C (62.6°F)). In the South-Eastern Anatolia region, summers are hot and dry, with temperatures above 30°C (°F). Spring and autumn are generally mild, but during both seasons sudden hot and cold spells frequently occur in the region. Turkey mean temperature for the 1971-2000 climatic periods is about 13°C (55.4°F) and has 0.64°C (33.152°F)/100 years increasing trend.

Kadioglu, (1997) analyzed and investigated the trend in surface air temperature data over Turkey. The analyses indicate that the mean annual temperature records in Turkey have a warming trend over the 1939 to 1989 period, but a cooling trend from 1955 to 1989. These trends in mean annual temperatures, however, are not statistically significant. Comparatively greater warming effects have occurred in spring and winter minimum rather than the maximum temperature records. A regional increase in the mean minimum temperature around 1955 is attributed to the urban heat island effect. In general, general circulation models (GCM) predictions are consistent with the sign of the trends only in Turkish climate records during the entire 1939 to 1989 period. Kadioglu and Saylan (2001) studied trends of growing degree-days (GDD) in Turkey. In this study they showed that spatially coherent, statistically significant and decreasing trends of GDD exist over the coastal areas of Turkey for summer and autumn. The Eastern Anatolia has also decreasing trends from November to March. In the other words, the vegetation growth has been decreasing over these areas for these seasons and months. On the other hand, there is no discernible increasing or decreasing vegetation growth for the Central and Southeast Anatolian regions of Turkey in all months and all seasons. These reductions in the accumulated growing degree-days above 5°C (41°F) are somehow inconsistent (at least in direction) with the predictions warmer air temperatures over Turkey with the three high resolution General Circulation Models 2CO2 simulations (IPCC, 1991). In further research, this trend analysis should be repeated to determine the variability in the length of the active growing season over this region. A possible result is an increase in the length of the active growing season should be brought about by warmer temperatures as predicted by the climate change scenarios. Spatially coherent and statistically significant trends of Cooling and heating degree-day appear in some regions of Turkey. In general, the sign of the trends is inconsistent with General Circulation Models (GCM) predictions (Kadioglu et al., 2001). Decreases in the diurnal temperature range are evident in Thailand, Turkey and Bangladesh. Most of the decrease in Turkey occurs during the autumn (Jones, 1995). These decreases result principally from increases in nighttime minimum temperatures and may be related to urban influences at some of the sites. Most come from the largest cities in the country.

2.9.2 Characteristics of rainfallTurkey receives most of the rainfall in the winter season (Figure 36). In this season, mean

temperature usually is below 5°C (41°F) and there is no too much evaporation, but summer rainfall is very limited and could not be enough to remove water deficit resulted from increased temperature and evaporation (Figure 37. The Aegean and Mediterranean coasts have cool, rainy winters and hot, moderately dry summers. Annual precipitation in those areas varies from 580 to 1,300 millimeters, depending on location. The Black Sea coast receives the greatest amount of rainfall. The eastern part of that receives 2,200 millimeters annually and is the only region of Turkey that receives rainfall throughout the year (Figure 38). Turkey's diverse regions have different climates because of irregular topography (Figure 39). Taurus Mountains are close to the coast and rain clouds cannot penetrate to the interior part of the country. Rain clouds drop most of their water on the coastal area. As rain clouds pass over the mountains and reach central Anatolia they have no significant capability to produce of rain. In the Eastern region of Anatolia, the elevation of mountains exceeds 2500-3000 m. Northern Black Sea Mountains and Caucasian Mountain hold the rain clouds, and therefore the area is affected

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by the continental climate with long and very cold winter. A big difference is observed when the total rainfall between coastal and inland stations, are compared. The Black Sea coasts (Rize, Hopa) receive 2,200 mm rainfall while Konya and Iğdır 250-300mm. Annual precipitation amount of Turkey is mainly determined by elevation. The Aegean and Mediterranean coasts have rainy conditions in winters but dry in summers. Annual precipitation in those areas varies from 580 to 1,300 mm. The Black Sea coast receives the greatest amount of rainfall and is the only region of Turkey that receives rainfall throughout the year. Annual average precipitation of Turkey for the 1971-2000 climatic periods is about 640mm and has 29mm/100 years decreasing trend. Jacobeit, (2000) showed for the last three decades some rainfall increases in autumn (western Iberia and southern Turkey), but dominating decreases in winter and spring.

Different rainfall intensity characteristics between the seasons in Turkey are related to the north-south directed oscillations of the polar front systems and the low pressure systems (www.dsi.gov.tr/english/congress2007/chapter_4/105.pdf). Turkey, in general, is affected by the polar front and the low pressure systems from the end of October to May. (Meteorological Office 1962, 1963). During the frontal systems pass through the country, the short-term weather conditions having warm and cold periods as well as rainy and dry periods occur. Developing phase of the frontal system and the path followed affects the distribution of rainfall intensity and frequency. The polar frontal systems hanging down Mediterranean basin causes air masses to warm and have higher relative humidity. The rainfall intensity also depends on the orographic lifting in western and southern parts of the country occurred by these unstable air masses. The other system affecting on Turkey in winter is the continental polar air mass. This system extends through Eastern Mediterranean basin. Rain showers occur along the frontal system zone formed by continental polar air mass and the tropical air mass. Moreover, this frontal system causes less intensive rainfalls and snows in the inner parts of the country. When the warmer conditions occur on the land, the polar front system withdraws to the northern latitudes and the country is affected by the tropical air masses (Figure 40). As Asor high pressure extends over Europe, the southern part of Turkey is affected by thermic low pressure system. These conditions are the major factors causing decrease in summer rainfall in Turkey (Akyol 1944). The gradient difference between Asor high pressure and Basra low pressure creates an appropriate condition that for the northwesterly wind. Both enhanced humidity of the air masses passing over Black Sea and rise of these air masses along the Northern Anatolian Mountains cause orographic rains. Because of these conditions Black Sea shore has rainy summer seasons. This region also has rains associated with depressions passed over Black Sea in summer. Since the continental polar air mass does not have any effect in summer, the number of rainy days and rainfall intensity increase in the Northeast Anatolia. Frontal Mediterranean cyclones associated with the southwesterly air flows create favorable conditions for heavy rainfall and thunderstorms in the southern and western coastal parts of the country in late autumn and early winter. Orographic lifting is also a main cause of heavy rainfall production that intensity of the rainfall is further enhanced when the conditionally unstable and extreme moist air pushed upslope into higher terrain along the Mediterranean coast. During the winter season, she is under the influence of Siberian high pressure centre bringing cold air which produces heavy snow on the mountains while summer seasons it is under the influence of Arabian Gulf high pressure which results in high temperature over the continent. On the other hand, during the transition seasons atmospheric instability prevails producing severe floods across the country.

The spatial occurrence of floods is not spread uniformly over Turkey. The valleys all along the Black Sea and Aegean coasts are particularly threatened, i.e. the Black Sea, the Marmara and the Aegean geographical regions. Floods in western Turkey and in the coastal zones are mainly produced by heavy rainfall in combination with geomorphologic features. In the central and eastern parts of Anatolia snow accumulation plays an important role. Floods are due to heavy rainfall on the coastal areas of the western and southern parts of Turkey or to a sudden snowmelt in the eastern, mountainous

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part of southeastern Turkey. In the northern and central parts of the country, including the Eastern Black Sea Basin, both factors may occur depending on the time of the year. Precipitation types are frontal, orographic or convective (www.dsi.gov.tr/english/congress2007/chapter_4/105.pdf).

Kadioglu et al 1999 studied precipitation climatology of Turkey by harmonic analysis. In this study the maximum (minimum) precipitation records appear during December or January (August or July) all over Turkey (Kadioglu et al 1999). However, average monthly precipitation values range from 240 mm down to 50 mm, all in late autumn or winter seasons. As the coefficient of variation value approaches 100, by definition more precipitation events occur with local orographic or convective effects and they become more pronounced than synoptic scale frontal precipitation events. Only the first and second harmonics play dominant roles in the regional climatological variations in Turkey. In the majority of areas, the first harmonic explains more than 60% of the amplitudal variations. Even higher percentages appear along the Black Sea, Aegean Sea and Mediterranean Sea coastal locations. Intra-annual variation in the first harmonic is related to the influence from the intra-annual variation of water temperature in the seas surrounding Turkey. A large and relatively warm water body adjacent to the Turkish coast helps to explain the pronounced winter maximum in the near coastal areas. As for the continental areas, the contribution of the first component decreases. The second harmonic indicates a decreasing regional trend from the eastern towards western parts of Turkey. For Turkey it appears that this harmonic indicates the orographic precipitation features. It may equally well reflect the dominance of convective precipitation in the eastern continental parts of Turkey (Kadioglu et al 1999).

Aslan, (2004) studied the Climatological Changing Effects on Wind, Precipitation and Erosion: Large, Meso and Small Scale Analysis. She found that temperature, relative humidity, wind speed, pressure and precipitation variations have mostly been effected by meso scale fluctuations. Large scale phenomenon has also played an important role on the precipitation regime of the study area. Because of water-land temperature differences, wind speeds increase over Elazig and Malatya. The Increase of the relative humidity value over the study area coincides with the increasing evaporating rate from water surface of the dam. Other irrigation systems over The Southern part of the study area contribute to the evaporation rate and relative humidity variations. Because of the chemical ingredients of Van Lake water, evaporation rate over its surface is generally less than The Keban Dam. Large scale effects on precipitation, annual average of precipitation increases over Van. Meso scale circulation decreases wind speed. They increase relative humidity values over Van.

Tayanc and Toros (1997) investigated the effect of urbanization on the regional climate change in four big cities in Turkey. They observed a significant relation between temperature and urbanization, but they found no relation between annual precipitation and urbanization. Hence, they argued that the cities are not big enough to affect the precipitation trends. Kadioglu (1997) investigated the influence of urbanization on precipitation in the Marmara region, and found that there was an increase in the number of precipitation days because of the increase in the number of condensation nuclei in the cities. It was also observed that the number of heavy precipitation days decreased. It is also pointed out in that there is a remarkable increase in the number of precipitation days in the downwind eastern parts of big cities such as Istanbul and Bursa. Cicek and Turkoglu, (2005) studied urban effects on precipitation in Ankra. They found that at both the urban and rural stations, an increase was observed in the number of precipitation days and light precipitation days within years. However, the number of heavy precipitation days increased at the station with urban character (Ankra meteorological station), while it decreased at the station with rural character (Esenboga meteorological station). A 50% increase was observed in the number of heavy precipitation days at the urban station (Ankra meteorological station) in comparison with that of the rural station (Esenboga meteorological station). The increased trend in the precipitation and light precipitation days at both station may be related to changes in climate.

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However, the increase in the number of heavy precipitation days only at the station with urban character (Ankra meteorological station) may be due to urbanization.

2.9.3 Circulation pattern affect climate of TurkeyOver the last several years, several studies on climate variability, the effects of the North Atlantic

oscillation (NAO), and El Nino/La Nina events in Turkey have been performed (Ropelewski and Halpert, 1989; Kiladis and Diaz, 1989; Turkes, 1998; Kadıoglu et al., 1999; Karaca et al., 2000; Cullen and deMenocal, 2000; Karaca et al., 2000; Kahya and Karabork, 2001; Turkes and Erlat, 2003; Unal et al., 2003; Karabork and Kahya, 2003). The data from these studies show that, during positive NAO years, Turkey experience significantly cooler and drier conditions, whereas warmer and wetter conditions dominate during negative phases of the NAO. Turkish temperature and precipitation time series show decreasing trends during the 1980s, which are consistent with the persistently positive NAO index during that time (Cullen and deMenocla, 2000).

Ropelewski and Halpert (1989) first identified the Mediterranean Middle East (which partly covers Turkey) region as a coherent area suggesting ENSO-related precipitation responses and pointed out that the ENSO–precipitation relationships were unstable over time. However, their findings for this region underscore the necessity of examining precipitation time series. At the same time, Kiladis and Diaz (1989) indicated wetter than normal conditions during the El Nino autumn season over the eastern part of Turkey, wetter than normal conditions during the El Nino winter season over the northeastern part of Turkey, and drier than normal conditions during the spring season of the year following an El Nino year over the eastern part of Turkey. After the foregoing two global-scale studies, Turkes (1998), using a methodology based on the Student’s t -test for differences between warm- and cold-event-related composite Turkish rainfall anomalies, identified some regions without a significant ENSO signal and emphasized the warm (cold) event responses appearing as a decrease (increase) in rainfall during the event years. Kadioglu et al. (1999) investigated monthly total precipitation variation using the superposed epoch method on the data set of 108 meteorological stations in Turkey and found that much of the month to month variability was related to El Nino events. They indicated that El Nino events depress and enhance precipitation variability in the southern and northwestern parts of Turkey respectively. Moreover, Karaca et al. (2000) compared the 1982–83 El Nino year with the 1988–89 non-ENSO year using 20 precipitation stations over Turkey with respect to total duration of blocking and number of blocking cases. They determined that precipitation totals were much higher during the winter of an ENSO year, but stressed the need for further studies to confirm this. Nevertheless, an overall evaluation of the outcome of previous studies can be made that none has come up with conclusive implications regarding the existence of SO-related signals in Turkey’s climate. An exception is Kahya and Karabork (2001), who documented the El Nino and La Nina related signals existing in streamflow patterns in a conclusive manner using 76 gauging stations across Turkey. They identified two distinct regions, one in western Turkey and the other in eastern Turkey, both of which are assumed to be noticeably affected by the tropical thermal forcing events.

Karabork and Kahya, (2003) investigated the teleconnections between the extreme phases of the southern oscillation and precipitation over Turkey. They found that coherent and significant precipitation responses to both the extreme phases of the southern oscillation (SO) are found in two core regions, namely western Anatolia (WA) and eastern Anatolia (EA). The geographical is extent of the two regions, together with a defined signal season for each tropical event, are identified. For WA, the April–July wet period during El Nino events is the season when the teleconnection is strong and consistent. For EA, the February–June wet period during El Nino events is found to be the signal season having high rates of coherence and consistency. The occurrence of the signal season (the dry period of April–October) during La Nina events appears to be less significant in EA according to the hypergeometric model. Moreover, the annual cycle analysis implies somewhat of a modulation of

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regional precipitation in the WA and EA regions during the relevant signal season. From other perspectives, correlation results of seasonal precipitation and seasonal SO index values confirm the implied teleconnections, and the powers of line spectra corresponding to the El Nino occurrences supply some indications. The final aim of this work is to show some guidance for quantification of the SO-related precipitation teleconnections for the core regions by examining shifts in precipitation amounts at various percentiles as a function of the SO extremes. Overall, the results of this investigation are in good agreement with previous relevant studies (especially global-scale type) that try to understand complex global circulation dynamics. In conclusion, mid-latitude precipitation responses to the extreme phases of the SO are detectable in the climate of Turkey.

Barrett, (2006) studied relationship between sea-surface temperature anomalies and precipitation across Turkey He found that for the majority of sites across Turkey, precipitation has no relationship with SST anomaly in both the Black and Mediterranean Seas. Precipitation is, in a basic sense, a function of local vertical motion and water vapor quantity. These two variables are influenced by a variety of global-, synoptic-, and meso-scale features, including planetary waves, mid-latitude cyclones, upper-tropospheric subsidence, mid-tropospheric humidity, local topography, and local soil moisture. Therefore, it is not surprising to find little correlation between SST and precipitation. However, it is interesting to examine the few sites and few months that do exhibit weak correlation. In the summer months of June and July, precipitation is mostly generated by random convective cells. As SSTs increase, boundary layer relative humidity will also increase. The stations that reported weakly positive correlations are mostly located in an arc across east-central Turkey, from NIG in the south-central to KAR in the northeast. This area is mountainous and its climate continental (Türkeş and Erlat, 2003). It is possible that in June and July, local orography acts to generate convective updrafts, and the greater boundary layer relative humidity (which must be transported to these locations, as they are not adjacent to either sea) enhances the convective precipitation. In this case, positive SST anomalies can be considered as one of the forcing for increased summer precipitation over the central and eastern interior of Turkey. In the transition months of March-April and August-September, weakly negative correlation coefficients are found in an arc through northwest to northern to northeastern Turkey, from IZM to IST to RIZ. This area is in the Black Sea and Mediterranean Sea climate zones (Türkeş and Erlat, 2005). During these months, positive SST anomalies are possibly related to increased subsidence and thus increased solar radiation. The increased subsidence would act to suppress cloud cover and precipitation. Thus, in this case, positive SST anomalies are possibly responding to the same external forcing that causes decreased precipitation, and the two are therefore weakly negatively correlated.

2.9.4 Future Climatic Changes in TurkeyTurkey and its region will undergo a warming in all seasons for both the SRES A2 and B1

emissions scenarios (portal.worldwaterforum5.org/.../worldregions/In%20and%20Around%20Turkey /.../Climate%20Change.ppt). By the end of this century, regional model results indicate an increase in temperature ranging between 2 to 4 °C under A2 and B1 scenarios with regional and seasonal differences. The highest warming will be in summer in southern parts, especially Southeastern Anatolia Region of Turkey, Iraq, Iran and Greece. Hot spells above 35 °C are projected to increase in summer season in southern Turkey, Syria, Iran, Greece and Balkan States.

Severe reductions are projected in winter precipitation which is very important for water resources. For the 2041-2069 period, there will be an increase in northern Turkey, Greece, Balkan States, Iran and Azerbaijan while a decrease in South of Turkey, Russia and Ukraine. For the period of 2071-2099, precipitation is projected to increase in North and decrease in South. Annual precipitation will increase over Turkey, Greece, and Balkan States until 2040 and strong increase over Balkan States between 30 and 50%. Most dramatic decrease occurs after 2071 over central and southern part of Turkey, Greece, west part of Bulgaria, Romania.

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2.10 Climate of IranIran with area of about 1,648,000 km2 (1,024,020 mi) is located in the southwest of Asia and lies approximately between 25°N and 40°N in latitude and between 44°E and 64°E in longitude (Figure 41). Iran’s important mountains are Alborz and Zagros ranges. Alborz and Zagros Chains stretch in northwest-northeast and northwest- southeast direction. These two ranges play an important role in the non-uniform spatial and temporal distribution of precipitation in the whole country (Nazemosadat and Cordery, 2000a,b). Iran's western borders are with Turkey in the north and Iraq in the south, terminating at the Shatt al-Arab, which Iranians call the Arvand Rud. The Persian Gulf and Gulf of Oman littorals form the entire 1,770 kilometers (1,100 mi) southern border. To the east lie Afghanistan on the north and Pakistan on the south.

On the basis of the Koppen climate classification (Ahrens, 1998), the Islamic republic of Iran is categorized as generally having arid (BW) and semiarid (BS) climates. This signifies that the annual precipitation is less than the potential annual loss of water through evapotranspiration (Nazemosadat and Cordery, 2000a,b). Iran has a hot, dry climate characterized by long, hot, dry summers and short, cool winters. Highland climates (H) are dominant over the foothills of these ranges (Nazemosadat and Cordery, 2000a,b). For example, at the base of Zagros Mountains the climate and vegetation generally represent semiarid conditions, while in the foothills, the climate becomes Mediterranean and the vegetation changes to chaparral. The central part of Iran, which is surrounded by the two above mentioned ranges, mostly comprises two great deserts called Dasht-e Lut and Dasht-e Kavir. These uninhabited deserts occupy around one-sixth of the total area of the country (Bina, 1994). In spite of severe dry conditions over these regions, the Zagros and Alborz Highlands which are classified as having a Mediterranean climate (CSb) as well as the coastal strip of the Caspian Sea, usually receive moderate precipitation. The occurrence of droughts and floods is common and the severity and hardships of these natural disasters have frequently hit rural regions as well as urban societies. Drought limits the cultivation of dry farming crops and affects the productivity of irrigated lands. 2.10.1 Characteristics of temperature

The climate is influenced by Iran's location between the subtropical aridity of the Arabian desert areas and the subtropical humidity of the eastern Mediterranean area. January is the coldest month, with temperatures from 5°C (41°F) to 10°C (50°F), and August is the hottest month at 20°C (68°F) to 30°C (86°F) or more. The climate is extremely continental with hot and dry summer and very cold winter particular in inland areas. Apart from the coastal areas, the temperature in Iran is extremely continental with relatively large annual range about 22°C (72°F) to 26°C(79°F) (Raziei,et al. 2005). Summers are warm to hot with virtually continuous sunshine, with high humidity on the southern coasts. Very high temperatures can be experienced along the Persian Gulf and Oman Sea. Winter weather is very changeable with some mild, wet spells but also some very cold periods with frost and snow. A small area along the Caspian coast has a very different climate, where rainfall is heaviest from late summer to mid winter but falls throughout the year.

Ghasemi and Khalili (2006) illustrated winter and summer temperature variability in Figure 42a and b, respectively, depicting the spatial distribution of the winter and summer mean air temperature for the period (1951–2000). Topographic features are considered to be the main source of temperature variability. As Figure 42a and b show, the lowest air temperatures in both seasons are centered over the mountainous regions in the north western areas. The highest air temperatures in winter and summer are observed in the southeastern and the southwestern parts of the country, respectively. During winter and summer the mean air temperature decreases from the southern areas toward the northern regions. On average, the Persian Gulf and Oman Sea coasts are warmer than the inner regions. It appears that, the northern half of the country is influenced more by cold polar air masses than the southern half. As a result, the difference between the winter (summer) mean air temperature in the northwestern and the

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southeastern (southwestern) areas is about 20oC (68oF), (18oC/(64.4oF) ), highlighting the variety of climates in Iran (Figure. 42).

Ghahraman, (2006) is studied time trend in the mean annual temperature at 34 synoptic stations in Iran. He found that the majority of the stations revealed increasing temperature; however, since the majority of the synoptic stations in Iran are located in airports and suburbs, it is hard to relate these findings to climate change and global warming. Land use change in suburbs, from agriculture and pasture to residential areas, is another cause for gradual increase in temperature. Yet, it is not possible to separate these 2 factors, while the synoptic stations in Iran are used extensively for irrigation water requirement computations. Land use change occurs slowly and, therefore, cannot lead to a jump in temperature time series. Meanwhile, constructing any instrument in a region may not necessarily lead to a jump in temperature (e.g., hydroelectric construction on the Danube River in Slovakia, as reported by Lapin, 1995). Based on the results of long run mean annual temperature, it can be hypothesized that the majority of the region will experience an increase in temperature in the future. Although the mean annual temperature trend lines in some stations were not significant, their positive signs may be a clue to temperature increase. This is especially true for the final years of the record. 2.10.2 Characteristics of rainfall

The country’s climate is mainly arid or semi-arid, except the northern coastal areas and parts of western Iran. Rainfall varies from season to season and from year to year. Precipitation is sometimes concentrated in local, but violent storms, causing erosion and local flooding, especially in the winter months (http://www.weatheronline.co.uk/reports/climate/Iran.htm). The occurrence of rainfall is unreliable and deviations from the mean are generally more than 40% (Goudie, 1990). The rainy period in most of the country is from November to May (winter and spring) followed by dry period between May and October with rare precipitation. The average annual rainfall of the country is about 240 mm with maximum amounts in the Caspian Sea plains, Alborz and Zagros slopes with more than 1,800 and 480 mm, respectively (Kappus, et al., 1978 ;Raziei,et al. 2005; Nazemosadat and Cordery, 2000a,b). Going inland at the central and eastern plains, the ranges of precipitation decreases to less than 100 mm annually depending on the location. Rainfall in autumn and spring usually occurs in the form of convective showers, and during the winter in the form of cyclonic storms (Kappus, et al., 1978).

Raziei,et al. (2005) studied annual rainfall variability in 79 meteorological stations of arid and semi-arid regions of Iran. Their results showed that high temporal variability of annual rainfall is a natural feature of this climate. Coefficients of variation in all stations indicated that the uniformity of rainfall in this region is very low due to high irregularities. Most of the stations (over than 60 %) were characterized with insignificant trend indicating that annual rainfall did not experience appreciable changes during 1965-2000 period. Therefore, it can be concluded that annual rainfall in this region was nearly stationary in the studied period. However, inherent irregularities and fluctuations in rainfall time series are the main factor responsible for scarcity of water resources and prolonged droughts. Lack of water in some years in conjunction with increased water demand in this region makes one to suspect to climate change. Except in foothills of Zagros and Alborz in west and north characterized by rugged topography and moderate climate, most of stations in center, south and east of the study area showed insignificant trends. In southeast corner of this region, most stations showed downward trend. Negative trend in annual rainfall in this region which has no major surface water resources and suffers from hot weather in over 7 months of the year produced water crises specifically in recent decade that the region experienced a prolonged drought.

From the synoptic aspects, the climate of most part of Iran is dominated by subtropical high in most part of the year. This phenomenon causes hot and dry climate in summer. The rainfall in the country is produced by Mediterranean synoptic systems, which move eastward along with westerly winds in cold season. Synoptic systems and year-to-year variation in the number of passing cyclones

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cause high variability in annual rainfall. Frontal Mediterranean cyclones associated with the westerly air flows produce most of precipitation in the whole country in late autumn and particularly in winter. In addition to the frontal Mediterranean cyclones, rainfall bearing systems called Sudanian cyclones which come from the southwest make an important contribution to increase annual rainfall amount of the west and southwest of the country. In northwest mountainous regions, convective and frontal thunderstorms are important atmospheric process responsible for rainfall in spring and early summer. These rainfall bearing systems just are active in the west portion of the country and have no more energy and moisture to pass far through east. These systems sometimes may reach central and east dry regions of the country when have no potential to produce rainfall due to long trajectory and loss of moisture. This region is the most drought prone area in the country due to high inter- and intra-annual irregularity in rainfall and high coefficients of variation. This region that account for over half of the country area, is surrounded by Alborz mountain range from the north and Zagros range from the northwest to southwest. Zagros range acts as a wall to prevent Mediterranean moisture bearing systems to pass through to the east. Hence these two ranges prevent the arid and semi arid regions of the central and eastern part of Iran from access to moisture. This phenomenon gives rise to high irregularity in rainfall in the study area. Lack of rainfall in May to October compounded with high temperature leads to high evapotranspiration and water deficit in this region. Prolonged drought in this area in recent years makes us wonder if we are facing to a drier climate. Increasing water deficit problem in conjunction with increasing population and water demands in this region gave the region a priority for study of climate change analysis. In areas farther to the east of the Persian Gulf, very heavy rainfalls associated with tropical cyclones may occur during the monsoon intrusion (Ardekani, 1972; Kappus, et al., 1978).

Comparative study climatic changes with contemporary basin river changes in Iran is studied by Ghohroudi, (2008). He calculated the polynomial regression for prediction of the changes in precipitation according to maximum and minimum of temperature. Changes in precipitation as related variation and maximum and minimum of temperature as independent variation were taken into consideration as follow;

PC= -.891+0.001P+0.313Tmax+0.165Tmin Where PC is the change in precipitation, P is a precipitation, Tmax is a maximum temperature and Tmin is a minimum temperature. For modeling of seasonal changing in climate between rain layer, maximum and minimum of temperature, changes in precipitation layer, changes in maximum and minimum of temperature, they were spatial corresponded by Cokriging method and each of these layers became changed into a matrix with 45051 records. The result obtain that although the seasonal and annually changes are present, the intention of changes in precipitation and temperature are present too so that it can be expect that precipitation have inclination to reduce its presence in winter and more appears in spring and leads its trends of changing from rain to snow. Minimum of temperature has increased tendency and with a little changes this condition is shown in maximum temperature. The minimum of temperature in most part of Country have increasing leap that in some parts appears to increasing trend. Accepting the increased trend of minimum temperature can be form a new method in management in water sources. In other word it can show this result that the capacity of snow resources is decreasing. Iran is a mountainous country and water sources in most catchments supplied by snow resources in spring and summer. The management in water sources must be looking for possibility of saving of spring flood on the other hand the maximum temperature is shown increasing leap so lost of water will be increased in spring and summer by evaporation. Also decreasing in leap of precipitation is in some region that have more wet climate like north and North West coasts of Iran. In result it can be expected that the surface of lakes will be smaller and because the base level goes down therefore rivers must eroded more to reach to base level then the capacity of sediment in behind the dams will be increased. Rising in temperature can make biologic changing and plant spices will face to increasing in

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water requirement and the vegetation cover will be decreased so that the penetration of soil will be more less and the capacity of underground water will be decreased and because of changing in type of precipitation so the expectation of destroyed flood will be increased and...Which phenomenon will impose Iran because of increasing temperature? It can be studied from different aspects.

2.10.3 Global indices affect the climate of Iran Many researchers are studied the effect of global climatic indices such as El Niño-Southern

Oscillation (ENSO), North Atlantic Oscillation (NAO) and/or Arctic Oscillation (AO) on climate of Iran. Nazemosadat and Cordery, 2000a,b found that the low and high phases of Southern Oscillation Index (SOI) were shown to be associated with high and low rainfalls in Iran, respectively. Drought and flooding are more likely during the episodes when both summer and autumn SOIs are less than (-5) and greater than +5, respectively. Nazemosadat and Cordery (2000a,b), Nazemosadat [2001a,b), and Nazemosadat and Ghasemi (2004) have shown that the (ENSO) phenomenon has a significant effect on winter and particularly autumn precipitation in Iran. These investigations suggest that, due to the intense warm (or El Niño) and cold (or La Niña) phases of ENSO, the intensity and predictability of dry and wet conditions in Iran are substantially altered. Past and future changes in precipitation and available water resources in Iran could, therefore, be associated with the trend in the Southern Oscillation Index (SOI) data, one of the most profound indicators of ENSO phenomenon. Nazemosadat.et al., (2006) demonstrated that for both precipitation and SOI time series, the change-point years occur near the mid-1970s. While the annual precipitation has usually increased for the period after 1975, the magnitude of the SOI was mostly negative for this period. This implicates that the increase in the frequency, strength and the duration of El Niño/La Niña episodes was generally associated with above/below normal precipitation over northern and particularly southern regions of Iran. The ENSO phenomenon was, therefore, introduced as a factor forcing climate change in Iran. Malekifard and Rezazadeh (http://balwois.com/balwois/administration/full_paper/ffp-465.pdf) are studied North Atlantic Oscillation (NAO) and its effects on temperature and precipitation over North-West of Iran. They found that atmospheric systems affecting on northwest of Iran are mostly Mediterranean. Intensifying and weakening of Azores high pressure and Icelandic low pressure have mark effects on Mediterranean systems. Comprehensive correlation is observed between wet (dry) years over the region with mark negative (mark positive) phase of NAO index. Also it is proved that the positive (negative) phase of NAO is accompanied with colder (warmer) winters. Since majority of climatic models predict the positive trending of NAO index in future seasons; regarding the correlation between this index and prevailing weather of northwest of Iran, more frequent droughts and colder weather is expected for this region. When Azores High pressure and Icelandic low pressure weekend, NAO index become negative and pressure gradient reduces over Atlantic. In this situation the relatively warm and moist air moves toward lower latitudes and lays over Mediterranean Sea. Wet and moist Mediterranean systems are strong in this episodes and associate with heavy rainfall over Eastern Mediterranean and also NW of Iran. Regarding the correlation between NAO and prevailing weather of northwest of Iran more frequent droughts and colder weather is expected for this region of Iran.

Ghasemi and Khalili, (2006) are studied the influence of the Arctic Oscillation (AO) on winter temperatures in Iran. By using the Median Sequential Correlation Analysis (MSCA) technique it is shown that the winter SAT is negatively correlated to the winter AO index for most parts of Iran. The winter AO index accounts for about 14% to 46% of the winter SAT variance. The positive (negative) SAT anomaly is found to be associated with the onset of the negative (positive) phase. The overall probability of below long-term mean temperature during the positive and the negative phases are estimated to be around 70% and 25%, respectively. For the negative phase, westerly winds that originate from the warm Atlantic regions increase over Iran and consequently positive temperature anomalies are found across the country. The positive AO phase is accompanied by northerly winds that

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allow continental polar and arctic air masses to move into Iran, producing below normal temperatures. The summer AO is found to explain about 25–32% of the winter SAT variance in Iran. The reason for this is explained by the significant correlation (0.38) between the summer and the following winter AO indices. These results indicate that the summer climate is linked to changes in atmospheric circulation which persist through to the following autumn and winter.

2.10.4 Sea surface temperature affect climate of IranNazemosadat (1998) and Safavi and Nazemosadat (2004) are studied Persian Gulf sea surface

temperature as a drought diagnostic for southern Iran. Khalili, (1992) found that about 30% of the total rain-bearing air masses coming to the country originate in north Africa, the Red Sea, and western Saudi Arabia. These air masses are known as the Sudan Current; they are categorized as tropical maritime. They produce a significant portion of the total annual rainfall over the southern parts of Iran. The occurrence of some heavy winter rainfalls in Shiraz, Fasa, Bushehr, and Bandar Lengeh is attributed to the movement of the Sudan Current toward Iran (Khalili, 1992). Nazemosadat et al. (1995) have annualized the relationships between Iranian seasonal rainfall and the Persian Gulf SSTs. Their study revealed that winter (January–March) rainfall over the southern and southwestern parts of Iran is negatively correlated with the Persian Gulf SSTs. Drought (flooding) spells over southern and southwestern parts of Iran are, therefore, expected when the Persian Gulf SSTs are above (below) normal. Shiraz is at the northern extremity of the areas whose rainfall is affected by the Sudan Current and is, therefore, suitable for such examination. Winter droughts and wet periods tend to occur for the episodes in which the Persian Gulf SSTs are above and below normal, respectively. In contrast, above normal rainfall generally occurred when the Persian Gulf SSTs were below normal. Overall, correlation analysis between rainfall and SST data, using various data lengths, has revealed that the fluctuations of SST account for about 40% of rainfall variability over the southern region (Nazemosadat, 1998). The Persian Gulf SSTs can hence be used as a drought diagnostic over southern parts of Iran.

3. Dust Storms over the Middle East Dust storms may cause a variety of problems. One of the major problems is a considerable

reduction of visibility that limits various activities, increases traffic accidents, and may increase the occurrence of vertigo in aircraft pilots (Marles, 1979; Hagen and Woodruff, 1973; Middleton and Chaudhary, 1988; Dyan, et al., 1991; Yong-Scung and Ma-Bong 1996). Other environmental impacts, reported in the literature (Hagen and Woodruff, 1973; Mitchell, 1971; Fryrear, 1981; Tsoar and Pye, 1987; Jauregui, 1989; Liu and Ou, 1990; Wheatan and Chakrauarti, 1990; Nihlen and Lund, 1995) include reduced soil fertility and damage to crops, a reduction of solar radiation and in consequence the efficiency of solar devices, damage to telecommunications and mechanical systems, dirt, air pollution, increase of respiratory diseases and so on.

Dust storms originate in arid and semi-arid regions, in particular the Sahara, Middle East and Mongolia. Dust storms throughout Saharan Africa, the Middle East and Asia are estimated to place more than 200 to 5000 million tons of mineral dust into the earth’s atmosphere each year (Tegen and Fung 1994). Dust storms in Saudi Arabia are known by the word ‘Shamal’ roughly translated as ‘North wind’, and known in Egypt by the word ‘Kamasine’. The winds can reach speeds as high as 80-95 kilometres per hour. Winds average 60-95 kilometres per hour and they move very fast. Middleton (1986) has reviewed the distribution of dust storms in the Middle East. In addition, Idso (1976) recognized Arabia as one of five world regions where dust storm generation is especially intense. Prospero and Carlson (1981) reports that a major zone of dust haze can be observed in the Arabian Sea during June, July, and August, and high levels of dust have been found off the Omani coast (Tindale and Pease 1999). Pease et al. (1998) suggested that the Wahiba Sands could be a major dust source.

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Although there are severe gaps in terms of the coverage by surface stations with dust storm observations, not least over the Rub Al Khali. Middleton (1986) demonstrated that the Lower Mesopotamian plains had the highest number of dust-storm days per year. Central Saudi Arabia had a moderate level of dust storm activity, with Riyadh recording an average of 7.6 dust storm days per year, and 76 days on average when blowing dust reduced visibility to less than 11 km. The TOMS data indicate that the Middle East is an important area of dust-storm activity, but rather than highlighting the Lower Mesopotamian Plains as a source region, it shows the importance of the Ad Dahna erg region of eastern and central Saudi Arabia (Herman et al. 1997; Torres et al. 1998). It also shows a small area of intense dust-storm activity with aerosol index (AI) values greater than 2.1 in the Saudi-Oman border region. This is the third most intense dust source that TOMS indicates in the world. It is an area of intense aridity fed by ephemeral rivers draining from the mountains of Yemen and Oman. The NCEP-NCAR reanalysis data shows the mean July to September seasonal winds (corresponding to the months of highest dust loadings in the TOMS data) to be light across Saudi Arabia, although with moderately higher winds on the coastal margins. A more thorough study of individual dust-storm events would be necessary to confirm the hypotheses that (dry) convection, occurring at the mesoscale, is an important mechanism for generating dust in this region. Such studies are restricted by access to wind data at an appropriately fine resolution. In contrast, the large-scale Asian Monsoon inflow, which is well resolved in datasets such as the NCEP–NCAR reanalysis, reaches a maximum off the coast of Oman, with the center of the low level jet in excess of 16 m.s-1. In all probability, the secondary maximum in dust loadings found over Oman relates to the concentration of the Monsoon inflow along the topography of Oman.

Dust or sand storms are caused by the outflow from low-pressure cells passing through a desert area from west to east. They can last for hours or days and cover small areas or entire countries. Lack of rainfall and warm temperatures during winter months set up conditions for spring sand storms by drying out the soil, producing fine particles easily swept up by winds. When winds reach 60 mph, a major sand storm is the result. In Iraq, in late spring and summer, hot dry winds from the north called “shamals” can produce gusts of 85 mph, raising clouds of sand and dust to several thousand feet (Davidson, 2003). Iraq has 20-25 such storms annually. Sand storms can occur throughout the year in the Middle East, but the prime months are May-September when hot, dry air from the Arabian Peninsula blows in as the “As Somoum” wind. In general, desert dust from sand storms contributes to cloud condensation nuclei, thereby enhancing rainfall potential. It also contributes to reflecting some 1Wm-2 of sunlight globally and 25 Wm-2 over the Arabian Gulf (Lashof et al., 1997). However, the overall impact of all mineral dust including that due to anthropogenic and natural sources like deserts is still poorly understood (Ramaswamy et al 2001).

Kutiel and Furman (2003) studied dust storms in the Middle East: Sources of origin and their temporal characteristics. The results presented in this study place the Middle East as one of the regions most affected by dust, in the world, next to Africa. Dust storms, or blowing dust are frequent during most of the year. However, there is a clear temporal trend of the timing of the main dust activity during the year from north-west to south-east. In region of southern Israel and the Mediterranean parts of northern Egypt the maximum activity is observed during winter and spring. Further south-eastward in region of western Iraq, western Syria, Jordan, Lebanon, northern Israel, the northern Arabian Peninsula and southern Egypt), this happens in spring. Finally, at the extreme southern and eastern region of the study area in region of Iran, north-eastern Iraq and Syria, the Persian Gulf region (Kuwait, Bahrain, Qatar and UAE) and the southern Arabian Peninsula (southern Saudi Arabia, Yemen and Oman), the maximum dust activity is observed in summer. Parallel to that delay, a considerable net intensification of dust activity is also observed. Thus outdoor activity of any kind in these regions, must take into consideration the limitations imposed by airborne dust. Idso (1976) recognized Arabia as one of five world regions where dust storm generation is specially intense. A source-receptor model has been used to identify potential

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source areas of mineral dust reaching eastern Mediterranean region by Gullu et al. (2005). The TOMS data indicate that the Middle East especially Ad Dahna erg region of eastern and central Saudi Arabia is an important area of dust-storm activity (Washington et al., 2003). The frequency of dust events is, in large part, the opposite of the frequency for precipitation events. Obviously, drier, hotter conditions favor more dust storms (Leslie and Speer, 2005).

3.1 Types of dust stormsThere are three types of dust storms that affect over Middle East;

A- Sahara depression (desert cyclone) formed in the lee side of Atlas Mountain and it occurs during spring.

B- Winter type: caused by steeping of the pressure gradient with southerly winds in the front of deep extra-tropical cyclones. In winter cold and dry southerly winds associate with deep depressions on the surface and it extends to upper levels about 1-2 days.

C- Cold front type: Caused by steeping of the pressure gradient winds in cold air in the rear of cold fronts associated with deep extra-tropical cyclones.

In spring dry and strong southwesterly winds tends to occur over northern Africa when a desert depression (Sahara depression) develops and passes over a strong baroclinic zone extending from west to east parallel to the southern Mediterranean coast. The features, which specify the Khamsine weather associated with desert depressions, in ascending order of importance, following El-Tantawy (1969), can be summarized as follows: a) Pronounced rise of temperature (about 8oC (46.4oF) above normal),b) Pronounced fall of dewpoint (about 6.5oC (43.7oF) below normal),c) Strong southerly wind that cause rising sandd- Active cloud formations, rainfall and sometime thunderstorm associated with a cold frontal passage.The above stated adverse weather conditions have attracted the attention of many meteorologists in Egypt. El-Fandy (1940) suggests that these depressions are formed through the oscillation of the quasi-stationary front separating the Mediterranean air from the desert air. The relationship between the jet stream and the formation of desert depression was studied statistically by El-Tantawy (1964), who suggested that Khamasine depressions can be arranged into two main types: a) Subtropical systems: These systems linked with the subtropical jet stream and form in an area of strong surface heating and underneath pronounced divergence around the exit region of the jet stream. He found that this kind of depression originated at different positions where the upper troposphereic flow allows for their formation, Moreover these depressions are steered in the direction of motion of these favorable upper tropospheric flow patterns. b) Extratropical systems: These systems have the same characteristics of the ordinary extratropical cyclones in middle latitudes.

In rather recent investigation of these cyclones Hassan (1974), Youssef (1988), Abdel Basset (2001), and Alpert and Ganor, (2001) detailed quantitative dynamical and energetic for particular cases of a Sahara cyclones. It was found that this type of sub-synoptic phenomenon with a relatively short wave length takes place over low latitudinal area of specific configurations with a period of the order 2 hours. The diurnal variation in such an area may play an important role in magnifying the amplitude of such disturbance due to the effect of surface resonance. In such a small scale disturbance, the rapid change is the more significant dominating factor than that of the wind change.

3.2 Synoptic analysis of dust storms in the Middle East Major dust and/or sand storms can be produced over the Middle East. These storms occur when the

sub-tropical jet stream pushing up from south of the Arabian peninsula and a polar front jet stream pushing down from the European continent (Figure 43 from, Taghavi and Asadi, 2007). These storms are most prevalent in the spring and summer when a prevailing northwesterly wind. The unique topography and human intervention within the region also contribute to the frequency and intensity of

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dust and sand storms in this area. The natural funneling of large air masses by the high mountains in Turkey and Iran combined with the high plateaus in Saudi Arabia, help to funnel air across the Mediterranean into the Persian Gulf. Specifically, dust and sand storms occur when the strong (mostly dry) storms-that often accompany well-defined cold fronts-stir up these particles (http// www.meted.ucar.edu). In most areas, dust storms can be classified by prefrontal and postfrontal winds that primarily occur in the winter, and summer dust storms caused by persistent northerlies. In the winter months, frontal passage leads to strong northwesterly winds on the backside of the front. The resulting dust storm is referred to as a Shamal, from the Arabic for north. The Shamal produces the most widespread hazardous weather known to the region.

On Tuesday, 25 March a strong dust storm limited visibility and in all likelihood reduced military activity over Iraq (Figure 44, from Grumm, 2003). This dust storm was relatively well forecast and has been referred to as a Shamal. It is unclear whether this event would truly classify as a Shamal as this term is often used to speak about a 40- day low intensity dust event in the Persian Gulf region. A Shamal is defined as “a summer northwesterly wind blowing over Iraq and the Persian Gulf often strong during the day but decreasing during the night.” This definition appears linked to heat lows and the intensity of a low-level inversion modulating the intensity of a low-level inversion modulating the winds in the boundary layer. Other, less strict, definitions suggest that the Shamal is a wind and dust storm. They begin in the spring, often defined to begin in February and are at peak intensity during the spring. A key feature with the more intense spring Shamal is an intense low-level jet (LLJ), the interaction with the subtropical jet, and a surface cyclone moving through the region. The longer duration events, which tend to be weaker, appear to be more thermally driven. The event of 25- 27 March 2003 clearly met the loser definition of a Shamal.

4. Climate change over the Middle East Climate change is “any change in climate over time, whether due to natural variability or as a

result of human activity (U.S. Government Accountability Office (GAO), 2007). Concentrations of greenhouse gases, including carbon dioxide, methane, water vapor, nitrous oxide, and fluorinated gases, such as hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, in the atmosphere are essential for life to exist on Earth(http://www.epa.gov/climatechange/emissions/index.html). However, increases in greenhouse gas concentrations, largely due to human activity, are causing the Earth’s surface to warm. Atmospheric concentrations of carbon dioxide, in particular, have increased to levels that are higher than previously seen in reliable recorded history (http://nationalacademies.org/onpi/ 06072005.pdf). Global warming impacts will likely include surface and ocean temperature increases, sea level rise, glacial melt, and more extreme weather events, such as droughts and floods, and less precipitation in some areas, including in the Middle East, with greater desertification.

There is solid evidence for global warming in the 20th century (CSIRO, 2006). In addition to the global-average surface warming of 0.6oC (33.08oF), the lower atmosphere and upper ocean have warmed, snow and ice cover have declined, global-average sea-level has risen 10 to 20 cm, high temperatures have increased, and frost seasons have become shorter (IPCC, 2001). Is the warming of the 20th century unusual or just part of natural variability?. Temperatures during the past 1,000 years can provide a measure of natural climate variability. While thermometer records are widely available for the last 140 years, earlier temperature records must be reconstructed from proxy data (tree-rings, sediments, ice cores and corals). Most proxy data are limited to the northern hemisphere. Mann et al. (1998) found that the 1990s were likely to have been the warmest decade, and 1998 the warmest year, of the past millennium in the northern hemisphere. Jones et al. (1998) reached a similar conclusion from largely independent data and an independent methodology. Crowley and Lowery (2000) found that medieval temperatures (between the mid-12th and early 14th centuries) were no warmer than mid-20th century temperatures. These results, and those of two other reconstructions (Briffa et al., 2001),

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are shown in the diagram below. Independent borehole temperature reconstructions (Pollack and Smerdon, 2004) also indicate that the recent warming is unusual in the context of the last 500 years. More recent research has shown that the late 20th century warmth in the northern hemisphere is unprecedented for at least the past 1,800 years (Mann and Jones, 2003). A claim that the pre-1900 variability may be underestimated by a factor of two (von Storch, et al., 2004) has been challenged (Wahl et al, 2006) Northern Hemisphere temperatures similar to those in the 20th century before 1990 may have occurred around 1000-1100 AD (Moberg et al, 2005). The robustness of multi-proxy reconstructions of temperature over the last millennium needs further investigation (Bürger and Cubasch 2005). Climate model simulations suggest that anthropogenic influences (greenhouse gas increases combined with aerosol increases) could lead to significant climatic change in this region during the next century. Temperature increases during all seasons, and shifting precipitation patterns are likely although their precise nature is far from certain (IPCC, 1996). The IPCC (2001) concludes that global warming over the past 50 years was mainly caused by human activities that have increased atmospheric concentrations of greenhouse gases. Middle East climate has varied considerably over the past 10,000 years (Issar 1995). The historical high correlation between human settlement and climate change in the Middle East (Issar 1995) attests to the sensitivity of systems in the Middle East to climate change.

The results of Nasrallah and Balling (1995) showed a linear warming of near 0.07°C (32.126°F)/decade across the Middle East for the period 1950-1990. The greatest warming is occurring in the spring, and the least warming is occurring in the winter. Analysis of spatial patterns reveals a statistically significant and positive relationship between temperature trends and the severity of human-induced desertification. The annual, summer, and fall regression equations show that in the absence of desertification, the region would have cooled over the study period. In addition, when the temperature trends are stratified by a binary overgrazing classification, Middle Eastern grid points affected by overgrazing are found to be warming faster than the grid points not affected by overgrazing, but the differences are not statistically significant. The results from the dry lands of the Middle East provide even more evidence of a local and regional warming signal associated with desertification and overgrazing. This signal must be considered in any attempt to link regional temperature trends to the atmospheric buildup of anthropo-generated greenhouse gases.Most scenarios computed within the last few years. Rahmstorf and Ganopolski, (1999) and Karl and Trenberth, (2002) show an increase of precipitation in the Middle East of about 100 mm/year until 2100 due to the global warming.

Mann (2002) noticed that the pattern of global warming of the past century does not show a strong influence in this region. Instead, patterns of natural low-frequency variability appear to dominate the region. One of these patterns is associated with the well-known “North Atlantic Oscillation” and leads to changes on inter-annual and decadal timescales. Another distinct pattern appears to relate to influences of low-frequency variability in the North Atlantic Ocean circulation and overlying atmosphere circulation, and describes changes that are predominantly multi-decadal in timescale. This latter pattern is especially important in predicting possible climate change scenarios in future decades in this region.

Alpert et al (2008) introduce in the paper entitled “Climatic trends to extremes employing regional modeling and statistical interpretation over the East Mediterranean” that, in the East Mediterranean (EM) recent climate trends include a decrease in winter temperatures and total precipitation amounts, accompanied by increases in the rainfall over the southern part of the region (IPCC, 2001) and extreme daily rainfall (Alpert et al., 2002, Yosef et al., submitted for publication). Some of these features are apparently caused by the global warming effects due to a significant increase in the concentration of greenhouse gases (GHG) in the atmosphere. Role of teleconnections appears to be essential. The North Atlantic Oscillation (NAO) index increase till the 90s explains the cooler and drier winters over the EM during the period (Ben-Gai et al., 2001; Krichak and Alpert, 2005b). The fact that the south EM

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was not influenced by a significant and dominant rainfall decreases over the region may be explained by positive contribution of the positive trend in occurrence of the East Atlantic/West Russia (EA/WR) pattern (Krichak et al., 2002; Krichak and Alpert, 2005a). Also, increases in intensity and number of El-Nino events were found to be positively correlated to rainfall in the region (Price et al., 1998). The rainfall increase in the southern part of Israel has possibly been affected by the local land-use changes over central to south Israel (Otterman et al., 1990, Ben-Gai et al., 1993, Perlin and Alpert, 2001). Other Mediterranean climate connections to tropical systems like the Indian Monsoon, Saharan dust, etc. were also pointed out recently by Alpert et al. (2005).

Also, in study of Alpert et al., (2008) large-scale predictions over the Mediterranean suggest: up to 35% rainfall reductions and 4oC (39.2oF) - 6oC (42.8oF) warming by 2071-2100. Regional climate model (RCM) findings support these and suggest further decrease in rainfall, increase in temperatures and a tendency to a more extreme climate. Much more detail can be derived from the RCM particularly with statistical downscaling as performed here over Israel with focus on a crucial small area the Upper Catchment of the Jordan River, North Israel. While most of the Mediterranean shows rainfall decreasing trends, there are rainfall increases over south/central Israel. These maybe associated with the significant observed increases in the frequencies of the Red-Sea Trough synoptic system. This finding, however, is not noticed by the global models. Another problem is that the maximum heating observed (since 1948) is found over the Mediterranean Sea, but is predicted for the 21st century to be over land. RCM simulations suggest also a significant factor of increase in the number of the heavy rain days (above 50 mm/d) over Israel - the Jordan River Basin. Averaged over the six stations in the north (except station Eilon all in the JR Basin) there is an average increase of 13.7 days and 2.7 days for the B2 and A2 respectively. Percentagewise these corresponds to +46% and +9%

The increase of extreme rainfall over Israel in spite of the decrease in rainfall totals reflects a change in the rainfall distributions. The trend has been associated with an increase in the frequency of occurrence of Red-Sea trough synoptic systems Alpert et al. (2004). It is not yet clear if the detected trend was a consequence of the global warming or was caused by natural climate variations. GCM simulations for the Middle East indicate higher future temperatures that will increase evapotranspiration and changes in climate patterns that might reduce rainfall in the region as a whole (IPCC-DCC 1999; IPCC-WGI 1999). In contrast, a few other recent simulations including the effect of aerosols in the atmosphere indicate a potential for lower temperatures in the Middle East, which may increase rainfall and water availability (Jones et al. 1997).

Evans, (2009) studied Global warming impact on the dominant precipitation processes in the Middle East. In this study, the ability of a regional climate model, based on MM5, to simulate the climate of the Middle East at the beginning of the twenty-first century is assessed. The model is then used to simulate the changes due to global warming over the twenty-first century. The regional climate model displays a negative bias in temperature throughout the year and over most of the domain. It does a good job of simulating the precipitation for most of the domain, though it performs relatively poorly over the southeast Black Sea and southwest Caspian Sea. Using boundary conditions obtained from CCSM3, the model was run for the first and last 5 years of the twenty-first century. The results show widespread warming, with a maximum of ~10 K in interior Iran during summer. It also found some cooling in the southeast Black Sea region during spring and summer that is related to increases in snowfall in the region, a longer snowmelt season, and generally higher soil moisture and latent heating through the summer. The results also show widespread decreases in precipitation over the eastern Mediterranean and Turkey. Precipitation increases were found over the southeast Black Sea, southwest Caspian Sea, and Zagros mountain regions during all seasons except summer, while the Saudi desert region receives increases during summer and autumn. Changes in the dominant precipitation-triggering mechanisms were also investigated. The general trend in the dominant mechanism reflects a change away from the direct dependence on storm tracks and towards greater precipitation triggering by

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upslope flow of moist air masses. The increase in precipitation in the Saudi desert region is triggered by changes in atmospheric stability brought about by the intrusion of the inter-tropical convergence zone into the southernmost portion of the domain.

5. Climate Change Impacts on Water Resources in Middle EastThe Middle East is the world’s most water-stressed region (UNDP, 2006). Climate change is

projected to cause sea level rise, more extreme weather events, decreased precipitation and, ultimately, less surface and ground water availability, all contributing to even greater water stress in the region, with severe environmental, economic, political and security implications. It is often assumed that since the Middle East region has very scarce water resources, the impact of climate change would be negligible (IPCC-WGII 1996). However, as noted before, water resources in the region are under a heavy and increasing stress. Any alteration in climatic patterns that would increase temperatures and reduce rainfall would greatly exacerbate existing difficulties. The general approach used for assessing the impacts on hydrologic regimes is to obtain climate data (representing various assumptions concerning projection period, GHG growth scenarios, etc) from GCMs and RCMs and use them as input to basin hydrologic models. However, if long-term data on rainfall runoff correlation and basin water balance are not available, complex hydrologic models should be avoided (IPCC-WGI 1996b; Strzepek 1998). Such data are unfortunately missing or unavailable in almost all of the countries under study (Lonergan and Brooks 1994, Brooks and Mehmet, 2000). While data are available for some major basins, data collection programs are recent and do not have the time span that allows reliable statistical correlations of inputs (precipitation, runon, etc.) and outputs (runoff, evaporation, etc.) to be developed for extreme conditions. In this study, potential climate change impacts are evaluated using GCM simulations. Subsequently, a water balance model is used for two representative regions in Lebanon to assess likely modifications in the hydrologic cycle.Several GCMs have been used to model the future climate for the whole planet under varying scenarios. Recent efforts focused on setting standard scenarios and time frames to ensure comparability of results from different GCM simulations (IPCC-WGI 1996a; 1997; Strzepek 1998). The relative success of GCMs in reproducing global weather patterns from past data is not necessarily an assurance that they will correctly predict the future climate even at the global scale.

In order to assess the implications of global climate change for Israel’s coastal region, Dayan and Koch (1999) developed a GCM-derived scenario, using procedures developed by the Climate Research Unit of the University of East Anglia for the IPCC (Intergovernmental Panel on Climate Change, IPCC 1996, the IS92a scenario). The four GCMs of the IS92a scenario were interpolated for stations, and a sub-grid analysis was done for each model, in order to develop scenarios for temperature and precipitation change. Their results predicted 80% to 90% sensitivity to the global climate change. That is, for every 1°C (33.8°F) change in the global mean, warming of 0.8°C (33.44°F) to 0.9°C (33.62°F) is anticipated in Israel, with a consequent reduction in precipitation. These results are similar to those of Palutikof and Wigley (1996) for the Middle East. However, the use of GCM-derived scenarios is highly problematic in a region that is highly sensitive to local- and regional-scale effects.

Segal et al. (1994) constructed a model of winter cyclone movement and overall water balance in the eastern Mediterranean region and found that a rise in temperature will lead to decreased precipitation due to redistribution of rainfall and an increase in evapotranspiration of up to 13% in summer and somewhat more in the winter. These results suggest an overall trend towards a greater water deficit. Dayan and Koch (1999) assessed a possible increase in storminess suggested by several authors and did not find conclusive evidence for increased frequency of storms or increased rain intensity. The scenario presented by Dayan and Koch (1999) for the coastal region of Israel pertains only to the country’s coastline, which is several kilometers wide3. Nevertheless, it is consistent with previous models (Palutikof and Wigley 1996; Segal et al. 1994), and probably applies to a wider area

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due to the relatively coarse resolution of the model used. Furthermore, since the coastal region is inhabited by 70% of the population, this scenario is valid for most of the Israeli population. The increased rainfall intensity will also increase surface run-off from urban areas. This, together with the increased run-off from open areas will generate more frequent and more powerful flash floods that beside damage to infrastructures and life will lead to an increased water loss, either to the Mediterranean or to the Dead Sea.

6. Circulation systems affect the climate of Middle EastThe variability of atmospheric circulation is the most important factor

determining changes in spatial distribution of temperature, cloudiness, precipitation and other climatic elements. Within the context of the discussion on climate change, the diagnostics of long-term circulation variability play an important role, particularly as the Intergovernmental Panel on Climate Change in 1992 termed this problem a ‘key topic for future research’ (Houghton et al., 1992). Natural climate variability is itself quite sizable in the region. While the El Niño/Southern Oscillation (ENSO) phenomenon, a dominant source of interannual climate variability over much of the globe, appears to have either an inconsistent (e.g., Rogers, 1984; Ropelewski and Halpert, 1987) or weak (e.g., Halpert and Ropelewski, 1992) influence on the climate of the region, there is recent evidence that the teleconnection of ENSO has indeed extended its reach into the Middle East in recent decades (Price et al., 1998). The North Atlantic Oscillation (NAO) atmospheric circulation pattern appears, by contrast, to exhibit a clear influence on the climate of the region on inter-annual and decadal timescales (see Cullen et al., 2002). Local and regional climate in mid-latitude are influenced by both large-scale atmospheric circulation and surface features (e.g. Lolis et al., 1999). As spatial distribution of surface characteristics is relatively stable, it would be expected that large scale climate plays an important role in causing changes in local climate. Studies of local climate change are often linked to variations in the atmospheric circulation (e.g. Yarnal, 1984). In characterizing large-scale circulation, an index which describes features of the large-scale circulation can be useful in explaining changes in surface climate elements (e.g. Kozuchowski, 1993). From section 2, one can conclude that the many circulation patterns such as NAO, ENSO, Arctic Oscillation (AO), etc., affect Middle East climate.

6.1 Impact of the North Atlantic Oscillation (NAO) on Middle Eastern ClimateBecause the signature of the NAO is strongly regional, a simple NAO index has

been defined as the difference between the normalized mean December-March sea-level pressure (SLP) anomalies at locations representative of the relative strengths of the Azores High (AH) and Icelandic Low (IL). A lower-than-normal (higher-than normal) IL and higher-than-normal (lower-than-normal) AH result in an enhanced (reduced) pressure gradient and a positive (negative) NAO index. During this +NAO (–NAO) phase, surface winds and wintertime storms moving from west to east across the North Atlantic are stronger (weaker) than usual (Figures 45a, 45b, from (http://www.ldeo.columbia.edu/res/pi/NAO/).

Swings in the NAO are produce changes in wind speed and direction over the Atlantic that significantly alter the transport of heat and moisture (Hurrell et al., 2003). During positive NAO index winters, enhanced westerly flow across the North Atlantic moves relatively warm and moist maritime air over much of Europe and far downstream across Asia, while stronger northerlies carry cold air

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southward and decrease land and sea surface temperatures over the northwest Atlantic (Figure 46). Temperature variations over North Africa and the Middle East (cooling), as well as North America (warming), associated with the stronger clockwise flow around the subtropical Atlantic high-pressure center are also notable. Changes in the mean flow and storminess associated with swings in the NAO are also reflected in pronounced changes in the transport and convergence of atmospheric moisture. Winters tend to be drier than average over much of Greenland, the Canadian Arctic, much of central and southern Europe, the Mediterranean and parts of the Middle East during positive NAO index winters, whereas more precipitation than normal falls from Iceland through Scandinavia (Figure 47).

Middle Eastern climate is known to have a significant relationship with North Atlantic Oscillation (NAO) on inter-annual and longer timescales (Cullen and Demenocal, 2000; Cullen et al., 2002). A positive NAO is related to stronger than average westerly winds across the middle latitudes of the Atlantic, and an intensification and shift of the North Atlantic storm track into northern Europe (Hurrel, 1995). Consequently, a positive NAO is often associated with lower than normal temperatures in the Middle East across southern Europe and in Greenland and higher than normal temperatures and precipitation levels across northern Europe during the winter (Wallace and Gutzler, 1981; Sarachik and Alverson, 2000). Opposite patterns of temperature, precipitation, and wind are usually observed with the negative phase of the NAO (Sarachik and Alverson, 2000; Arkin et al., 2002).

Anomalous temperature variations over North Africa and the Middle East (cooling), as well as North America (warming), associated with the stronger clockwise flow around the subtropical Atlantic high-pressure center are also notable during high-index NAO winters. Drier-than-average conditions prevail over parts of the Middle East during high NAO index winters, as well as over much of central and southern Europe, and the Mediterranean (Hurrell et al., 2000). The regional overprints of warming (e.g., in the Middle East) and extreme cold (e.g., Europe) that are superimposed on generally cold hemispheric conditions, in regions neighboring the North Atlantic, may be attributed to the NAO [see Luterbacher et al., 1999; Cullen et al., 2002), and Mann, 2002). Cullen et al. (2002) examined the relationship between the NAO and Middle Eastern climate and stream flow. They found that, inter-annual to decadal variations in Middle Eastern temperature, precipitation and stream flow reflect the far-field influence of the North Atlantic Oscillation (NAO), a dominant mode of Atlantic sector climate variability. Mann (2002) focused on the variations in the Middle East region and its relationship with larger-scale patterns of climate variability. He examined in detail the relationship between Middle Eastern climate and global climatic variations several centuries back in time. He was able to document the importance of at least two distinct patterns on the climate of the Middle East. One of these patterns is associated with the North Atlantic Oscillation (NAO) and dominated by inter-annual and decadal timescales. The other pattern is distinct from the NAO and more consistent with the atmospheric response to multi-decadal oceanic variations (Delworth et al 1993; Kushnir 1994; Mann and Park 1996). This suggests that patterns not easily resolvable in the short instrumental record (in particular, patterns distinct from the NAO) may be of increasing relative importance on progressively longer timescales, and are important to understanding climatic variations in the Middle East on multi-decadal and longer timescales. Eastern Mediterranean precipitation is examined in relation to the NAO and East Atlantic oscillation by Krichak et al. (2002). The results allow explanation of the observed reduction of the north Israeli precipitation by the East Atlantic positive trend during the period. Teleconnections associated with changing patterns of temperature and pressure anomalies over Israel during the second half of the 20th century were investigated by Ben-Gai et al. (2001). Relatively high, statistically significant, correlation coefficients of - 0.8 and +0.9 were found between the NAO Index anomalies and smoothed (5 year running mean) cool season temperature and surface pressure anomalies in Israel, respectively.

There is evidence of a connection between the Northern Hemisphere annular modes (Arctic Oscillation, AO or North Atlantic Oscillation, NAO) and eastern Mediterranean/Middle East climate

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variability in past centuries (Cullen and deMenocal, 2000; Felis et al., 2000; Rimbu et al., 2001; Cullen et al., 2002; Mann, 2002b; Luterbacher and Xoplaki, 2003; Rimbu et al., 2006). The combined analysis of proxy records derived from fossil corals of the northernmost Red Sea and simulations with a coupled atmosphere-ocean circulation model (ECHO-G) revealed an AO/NAO influence on the region’s inter-annual and mean climate during the late Holocene and last interglacial period 2900 and approximately 122000 years ago, respectively (Felis et al., 2004). Also significant is the red portion of the NAO power spectrum, which may exhibit significant Middle East region, in order to reveal the physical mechanism for the linkage between the AO/NAO and variations of SST and hydrologic balance in the northern most Red Sea. This combined analysis of the proxy record and instrumental climate data revealed that the region’s inter-annual to decadal climate variability is controlled by a high-pressure anomaly over the Mediterranean Sea that is associated with the AO/NAO, especially during the winter season. This high-pressure anomaly favors an anti-cyclonic flow of surface winds over the eastern Mediterranean, thereby controlling the advection of relatively cold air from southeastern Europe towards the northern Red Sea (Rimbu et al., 2001).

The influence of North Atlantic Oscillation (NAO) is much weaker on stream flow over River Nile (Hasanean, 2003). Changes in stream flow of the Tigris and the Euphrates Rivers (Turkey, Syria, and Iraq) are shown to be associated with the North Atlantic Oscillation (NAO), a large-scale mode of natural climate variability which governs the path of Atlantic mid-latitude storm tracks and precipitation in the eastern Mediterranean (Cullen and deMenocal, 2000). Composite indices of Turkish winter (December-March) temperature and precipitation are developed which capture the inter-annual-decadal climate variability for the Tigris-Euphrates headwater region, a significant source of freshwater for Turkey, Syria and Iraq. These indices are significantly correlated with the NAO, with 27% of the variance in precipitation accounted for by this natural mechanism. As evidenced by the recent widespread drought events of 1984, 1989 and 1990, the Tigris-Euphrates stream flow also exhibits significant, ±40% variability, associated with extrema. Negative Index is correlated with: increased precipitation and stream flow in Turkey (Visbeck, 2003). NAO is reduced stream flow volume in the Middle East (Cullen and de Menocal, 2000). Precipitation in Turkey is well correlated with the NAO. As a result spring stream flow in the Euphrates River varies by about 50% with the NAO. An upward trend in the NAO will lead to drought conditions in the Middle East. Cullen et al., (2002) used a new sea surface temperature (SST) based index of the NAO and available stream flow data from five Middle Eastern rivers. They showed that the first principal component of December through March stream flow variability reflects changes in the NAO. However, Middle East rivers have two primary flooding periods. The first is rainfall-driven runoff from December through March, regulated on inter-annual to decadal timescales by the NAO as reflected in local precipitation and temperature. The second period, from April through June, reflects spring snowmelt and contributes in excess of 50% of annual runoff. This period, known locally as the khamasine, displays no significant NAO connections and a less direct relationship with local climatic factors, suggesting that stream flow variability during this period reflects land-cover change, possibly related to agriculture and hydropower generation, and snowmelt.

6.2 Impact of the El Nino Southern Oscillation (ENSO) on Middle East ClimateNatural climate variability is quite sizable in the Middle East region. While the El Niño/Southern

Oscillation (ENSO) phenomenon, a dominant source of inter-annual climate variability over much of the globe, appears to have either an inconsistent (e.g., Rogers, 1984; Ropelewski and Halpert, 1987) or weak (e.g., Halpert and Ropelewski, 1992) influence on the climate of the region. There is recent evidence that the teleconnection of ENSO has indeed extended its reach into the Middle East in recent decades (Rodo et al, 1997; Price et al., 1998; Turkes, 1998; Nazemosadat and Cordery, 2000a,b;

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Hasanean, 2003; Nazemosadat et al., 2006).The authors note evidence of an increase in recent decades in the influence of El Niño on precipitation patterns in the middle east.

There seems to be a connection between past and present Nile flood maxima and ENSO events (Eltahir and Wang, 1999; Kondrashov et al., 2005). The coherency between ENSO index and the Nile flood has a distinguished peak at the time scale of 4-5 years, which is close to the ENSO time scale (Eltahir and Wang, 1999). The possible physical connections are discussed in Eltahir and Wang (1999) and Kondrashov et al. (2005) as well. Hasanean (2003) studied the teleconnection between global climatic events, atmospheric circulation change and stream flow over the River Nile. He found inverse relationship between 3-months seasonal cycle stream flow and ENSO over River Nile. Unlike other seasons, the spring season of stream flow indicates positive with ENSO and Tropical Atlantic sea surface temperatures.

Mariotti et al. (2002, 2005) found that autumn (winter) Southwest Asia (SWA) (the traditional European names the Middle East and the Near East) precipitation above (below) normal during Elnino (La Nina). Anomalous onshore moisture flux from Arabian Sea into SWA during periods is of above (below) normal precipitation in SWA. Also, in SWA, rainfall anomalies appear connected to moisture flux anomalies in the Indo-Pacific region and the anomalous circulation over south Asia

Vorhees et al. (2006) found that convective (subsidence) component of MJO in eastern Indian Ocean (IO) leads to below (above) normal precipitation in SWA. Also, upper-level Rossby-Kelvin response to MJO extends over SWA. Only speculated on how MJO affects low level circulation and moisture transports into SWA.

Nazemosadat et al (2006) explained the role of the Indian and Pacific oceans on the climate variability of the Middle East. He lamented that due to huge amounts of heat inserted into the tropical Pacific atmosphere during periods of higher than normal SSTs, the wind circulation changes from surface to upper levels affecting the whole globe. El Niño conditions weaken the Indian monsoon and warm the Arabian Sea thus weakening the pressure gradient and reducing the wind speed. La Niña conditions make the pressure gradient stronger thus bringing more rainfall in the region. However, there is need to study more on the impacts of ENSO on precipitation in different parts of the region.

6.3 The role of highs pressure (Siberian and Subtropical high pressure) and Indian low pressure on Middle Eastern Climate

During the past several years, the impacts of monsoon condensational heating on the formation of the subtropical anticyclone have been reported by different studies (e.g. Liu et al., 2001; Rodwell and Hoskins, 2001). The summer subtropical circulation in the lower troposphere is characterized by continental monsoon rains and anticyclones over the oceans. Rodwell and Hoskins (2001) demonstrated the duality between the monsoon condensational heating and the low-level subtropical circulation in the sense that either one would be very different without the other. The precipitation increases near the North–East Coast of the Mediterranean Sea, from the Adriatic Sea to the Black Sea, related to low-level wind convergence (Laurent. and Li, 2006). The oscillation and strength of Asiatic monsoon low pressure and subtropical high pressure play an important role in rainfall over the River Nile (Hasanean, 2003). The duration of the rainfall amount depends upon both location of the inter-tropical convergence zone (ITCZ) and the meridional sea surface temperature (SST) gradient in the tropical Atlantic (Hasanean, 2003). Hasanean (2005) defined a robust subtropical circulation index (SCI) as the difference between the North Atlantic subtropical high and the Indian monsoon low. The SCI is negatively correlated to air temperatures over Egypt and is associated with large-scale climate indices of the tropical and subtropical Atlantic

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sector. The subtropical high is being the dominant atmospheric circulation system in the lower troposphere and controlling the whole of the east/west and mid-Atlantic (Hasanean 2005). The subtropical high pressure also exerts a powerful influence on climate over middle latitudes. The SCI is associated with the Hadley cell index patterns whose linear combination can explain year-to-year variability in the SCI. Also, the pattern of SSTs over the Tropical Atlantic (TATL) (10oS–10oN, 0o – 360o) and the North Tropical Atlantic (NATL) (5o –20oN, 60o –30oW) is associated with SCI. These relationships between the TATL index and the NATL index with the SCI suggest that the change of the SLP of the SCI induced the change in the tropical north and the tropical Atlantic SSTs. The summer ENSO has links with the SCI, while there is no connection between the SCI and the summer NAO index. Variations in local climate may be responding to changes in circulation index strength, but may also be due to competing influences from other circulation types. Some of the variability in the correlation between temperature and circulation may be due to different circulation types influencing temperature. While zonal circulation usually has a dominant influence on temperature, there were periods such as the 1920s when meridional circulation appeared to have greater influence (Slonosky and Yiou, 2002). Wang (2002) noted that the changes of the Atlantic subtropical high induce variations of the northeast trade winds on its southern flank and then affect the tropical North Atlantic SST anomalies. The atmospheric circulation cell changes result in anomalous ascending motion in the tropical North Atlantic. It decreases the SLP and pushes the subtropical anticyclone northward, then decreases the northeast trade winds and latent heat flux. This increases the tropical North Atlantic sea surface temperature anomalies. Also, Wang (2002) noted that the tropical Atlantic meridional gradient mode is associated with the variations of the Northern Hemisphere Hadley circulation in the tropical North Atlantic and south tropical Atlantic. Local changes in the meteorological variables in the mid-latitudes are mainly controlled by the atmospheric circulation (Hurrell and Van Loon, 1997). As a consequence, a significant fraction of local variability can be explained by large-scale oscillation patterns. Some previous studies found that almost half of the wintertime (December–February) temperature variance over Egypt could be explained by the East Atlantic–West Russia (EAWR) index and NAO (Hasanean, 2004).

Fu et al., (1999) examined the behavior of the surface fields over the ocean during rapid warming of the 1920s. The Northern Hemisphere continental record shows that both middle and high latitudes experienced rapid warming in the early 20th century warming interval (the 1920s and 1930s. Temperature data for northern tropics, while displaying similar general characteristics, exhibit some differences with regard to timing and rates of change. There is a suggestion of weakening of the westerlies and the trade wind system in the 1930s, following an intensification of the westerlies across the North Atlantic during the previous two decades. There is some indication that the North Atlantic and North Pacific high-pressure systems shifted northward. Coincident with this northward shift of the subtropical highs, typhoons in the Northwest Pacific and hurricanes in the North Atlantic became more numerous in this period of rising temperature, which we suggest is linked to a northward shift of the respective near-equatorial convergence zones. Concomitant to the weakening of the westerlies and trade wind systems, the Asian monsoon troughs deepened substantially, a situation generally favorable to the development of active monsoons. It is thought that the combination of these two features enhanced continental monsoons and implied lowered vertical wind shear over the oceans would tend to enhance the release of latent heat in the tropics, representing strengthened Hadley and Walker circulations, which may have been at least partly responsible for greater aridity in subtropical land areas of both hemispheres during this period. The latter is also consistent with an expansion and/or strengthening of the subtropical high-pressure belt into the continents.

Hasanean (2008) proposed of some of the principal mechanisms associated with the extreme warming during August 1998. Inverse relationship between

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pattern of zonal index (ZI) and pattern of surface temperature over Egypt is found. Concerning atmospheric circulation system, the correlations with Indian monsoon and surface temperature over Egypt show different structures. The August 1998 exhibits strong negative correlation, whereas the weaker positive correlation is simultaneous in August 1997. Hence in the period of extreme warming (August 1998) the trough of Indian monsoon is deepened significantly. The surface temperature is associated with subtropical high pressure center index pattern (SHCI). This relationship between surface temperature and SHCI suggests that the change of the sea level pressure of the SHCI induced the surface temperature change. During August 1997, the SHCI is intensified and highly affects surface temperature over Egypt and in turn supported the area by cold air. During August 1998 the situation is reversed. There is a clear duality between the Indian monsoon low pressure index (INDMI) and SHCI. The mid-latitude temperature response to a subtropical Hadley circulation anomaly is dominated by enhanced power in low-frequency planetary waves (Hou, 1998). The increase in temperature in Egypt may be associated with the weakness in Hadley cell circulation. Significant negative relationship between Hadley cell index and surface temperature is found during August 1998. Hadley circulation affects North Atlantic subtropical high pressure and the recent trend is argued in connection with recent global warming. During extreme warming of surface temperature the intensity of Hadley cell circulation can lead to intensify the subtropical jet stream. Extreme warming may be related to the change of location and strength of the subtropical jet stream. High significant negative, positive correlations between subtropical jet stream index and surface temperature pattern over Egypt during August 1998, August 1997) are found. The anti-correlation between surface temperature and subtropical jet stream index may be related to the effect of the ZI on the subtropical jet stream. The strength of subtropical jet stream is shifted to the northward and weakened during August 1998, while it is shifted to the southward and intensified during August 1997.

Almazroui et al (2009) found that the climatological pressure systems that dominated on Kingdom Saudi Arabia (KSA) area in winter are the Siberian high, the red sea trough, the subtropical high and the westerly trough. While the pressure systems that dominated on KSA area in summer are the Indian monsoon low, the thermal low and the subtropical high. In the second transitional season (Autumn) the pressure system that appeared and dominants are the Red sea trough, the Siberian high and the easterly trough. On upper air levels (500 hPa) the climatological pressure systems that dominate on KSA area during the continuous monthly period from May to October is the subtropical high. While in the other months the Zonal flow appeared and dominants. The analysis of the horizontal distribution of some meteorological variables illustrate that the maximum heating is associated with the location of low pressure systems And the larger heating occurs in summer over the Indian content and the eastern part of KSA in association with the location of Indian monsoon low. The core of the subtropical jet is stronger during the winter than the other seasons and located near 27.5oN, while it’s weaker during the summer and shifted north ward to appear at 43oN. The maximum relative humidity concerns in association with the location of low pressure systems and the regions of seas and oceans in all seasons.

The annual migration of the ITCZ and seasonal development of the monsoon winds are key-components of the climatology in the Indian Ocean and the surrounding areas (Fleitmanna et al., 2007). In spring the ITCZ migrates northward across the Indian Ocean and reaches its northernmost position during boreal summer (Figure 48a). From June to September, a strong low-level monsoonal

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air flow is generated by a strong pressure gradient between the low-pressure cell over the Tibetan Plateau and a high-pressure cell over the Southern Indian Ocean (Figure 48a). North of the equator, a strong southwesterly air flow, also known as the Somali or Findlater Jet (Findlater, 1969) transports large quantities of moisture, that is then released as monsoon precipitation over some parts of Southern Arabia and the Indian subcontinent. The release of latent heat through condensation of moisture is an additional and important forcing of the ISM as it further strengthens and maintains the surface low pressure over the Asian landmass (Webster et al., 1998). In autumn the ITCZ then retreats southward and reaches its southernmost position at approximately 25oS in January (Figure 48b). The reversed pressure gradient during the winter months generates the moderate and dry northeast monsoon.

Significant anti-correlation with Indian Monsoon is found over the Levantine Basin in summer season, as a part of a large structure extending over the Middle East, Northeast Africa and the Arabic peninsula, where maximum anti-correlation of about -0.65 is found (Raicich et al 2001). In summer 2008, the monsoon circulation over much of southern Asia was near normal except the stronger-than-normal south westerlies over northern Arabian Sea and northwestern India associated with the above normal Somali jet. (www.cpc.noaa.gov/...Monsoons/...Monsoons/.../AsianMonsoon_Summer2008.pdf).

6.4 The role of Jet streams on Middle East ClimateThe interaction between the polar front jet stream (PFJ) and subtropical jet stream (SJS) and its

role in the surface cyclogenesis has been investigated not only over the North African region but also over other subtropical regions (Whitney, 1977; Uccellini and Kocin, 1987; Hakim and Uccellini, 1992; Kaplan et al, 1998). More specifically, it was demonstrated that the coincidence of the divergence region in the right of the jet entrance of a PFJ streak with a region to the left of the SJS exit contributes to the initiation of cyclogenesis or the formation of very strong synoptic scale ascending motions. However, the exact role of the interaction between PFJ and SJS at the upper tropospheric levels on this type of cyclogenesis has not yet been fully determined. The Mediterranean climate is characterized by cold-season rainfall originating in the southward spread of the Jet stream during winter, accompanied by a southward shift of surface cyclone tracks (Zangvil and Drulan, 1990), which developed mostly during the cold season (Sahsamanoglou et al. 1991; Sarroni et al. 1996). Tropical Easterly jet stream was weakened in El Nino year and enhanced in La Nina year accompanying with the dry and wet condition respectively. During La Nina year, easterly wind is strong not only over North Africa but also over tropical Atlantic Ocean (Hasanean, 2003). Almazroui et al., (2009) and Alamodi et al (2008) investigated the role of subtropical jet stream on temperature and rainfall over Kingdom of Saudi Arabia, which they indicate that the core of the subtropical jet is stronger during the winter than the other seasons and located near 27.5oN, while it’s weaker during the summer and shifted north ward to appear at 43oN. Northward oscillation of subtropical jet stream play a big role in pulling hot dry air masses of the Arabian Peninsula and eastern Africa northward toward Kuwait and southern Iraq, and even to the southern border of Turkey (Nasrallah, et al 2004). The unusual movement of the SJS to the north of 40oN (north of Greece, Bulgaria, Turkey and over the Black Sea) had a big effect on the lower layers pulling the high pressure ridge northward.

7. ConclusionThe Middle East is a Mediterranean-type climate, characterized by a hot, dry summer and cool winter with short transitional seasons predominates in the northern, central, and western parts of the region. The eastern and southern parts of the region have a semi-arid to arid climate. Winter begins around mid-November and summer begins around the end of May. Rainfall occurs mainly during the winter months. Middle Eastern climatic conditions vary greatly, depending on the season and the geography.

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The well-watered highlands of Turkey and the mountains of Iran and Ethiopia are important as sources of the region's major rivers.

Middle East is dominated by dust or sand storm. Sand storms can occur throughout the year in the Middle East, but the prime months are May-September when hot. Dust or sand storms are caused by the outflow from low-pressure cells passing through a desert area from west to east. They can last for hours or days and cover small areas or entire countries. Lack of rainfall and warm temperatures during winter months set up conditions for spring sand storms by drying out the soil, producing fine particles easily swept up by winds. In region of southern Israel and the Mediterranean parts of northern Egypt the maximum activity is observed during winter and spring. Further south-eastward in region of western Iraq, western Syria, Jordan, Lebanon, northern Israel, the northern Arabian Peninsula and southern Egypt, this happens in spring. Finally, at the extreme southern and eastern region of the study area in region of Iran, north-eastern Iraq and Syria, the Persian Gulf region (Kuwait, Bahrain, Qatar and UAE) and the southern Arabian Peninsula (southern Saudi Arabia, Yemen and Oman).), the maximum dust activity is observed in summer. There are three types of dust storms that affect over Middle East; Sahara depression type, winter type and cold front type. These storms occur when the sub-tropical jet stream pushing up from south of the Arabian peninsula and a polar front jet stream pushing down from the European continent. The unique topography and human intervention within the region also contribute to the frequency and intensity of dust and sand storms in this area. The natural funneling of large air masses by the high mountains in Turkey and Iran combined with the high plateaus in Saudi Arabia, help to funnel air across the Mediterranean into the Persian Gulf.

Climate characteristics exhibit large changes from one area to another and across seasons and years. Average rainfall decreases from west to east and from north to south, ranging from 1,200 millimeters (mm) at the northern tip of the region to less than 50 mm in the desert areas. Temperature also varies across the area, generally according to latitude and altitude and by physiographic province. The greatest warming is occurring in the spring, and the least warming is occurring in the winter. Analysis of spatial patterns reveals a statistically significant and positive relationship between temperature trends and the severity of human-induced desertification. The annual, summer, and fall regression equations show that in the absence of desertification, the region would have cooled over the study period. Middle Eastern region affected by overgrazing are found to be warming faster than the region not affected by overgrazing. The results from the dry lands of the Middle East provide even more evidence of a local and regional warming signal associated with desertification and overgrazing. This signal must be considered in any attempt to link regional temperature trends to the atmospheric buildup of anthropo-generated greenhouse gases. Most scenarios computed within the last few years show an increase of precipitation in the Middle East of about 100 mm/year until 2100 due to the global warming. The results of model in the 21st century show widespread warming, with a maximum of ~10 K in interior Iran during summer. It also found some cooling in the southeast Black Sea region during spring and summer that is related to increases in snowfall in the region, a longer snowmelt season, and generally higher soil moisture and latent heating through the summer. The results also show widespread decreases in precipitation over the eastern Mediterranean and Turkey. Precipitation increases were found over the southeast Black Sea, southwest Caspian Sea, and Zagros mountain regions during all seasons except summer, while the Saudi desert region receives increases during summer and autumn. Changes in the dominant precipitation-triggering mechanisms were also investigated. The general trend in the dominant mechanism reflects a change away from the direct dependence on storm tracks and towards greater precipitation triggering by upslope flow of moist air masses. The increase in precipitation in the Saudi desert region is triggered by changes in atmospheric stability brought about by the intrusion of the inter-tropical convergence zone into the southernmost portion of the domain.

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Middle Eastern climate is known to have a significant relationship with North Atlantic Oscillation (NAO) on inter-annual and longer timescales. A positive NAO is related to stronger than average westerly winds across the middle latitudes of the Atlantic, and an intensification and shift of the North Atlantic storm track into northern Europe. Consequently, a positive NAO is often associated with lower than normal temperatures in the Middle East during the winter. Opposite patterns of temperature, precipitation, and wind are usually observed with the negative phase of the NAO. During high NAO index winters drier-than-average conditions are prevail over parts of the Middle East. Inter-annual to decadal variations in Middle Eastern temperature, precipitation and stream flow reflect the far-field influence of the North Atlantic Oscillation (NAO), a dominant mode of Atlantic sector climate variability. Due to huge amounts of heat inserted into the tropical Pacific atmosphere during periods of El Nino the wind circulation changes from surface to upper levels affecting the whole globe. El Niño conditions weaken the Indian monsoon and warm the Arabian Sea thus weakening the pressure gradient and reducing the wind speed. La Niña conditions make the pressure gradient stronger thus bringing more rainfall in the region. However, there is need to study more on the impacts of ENSO on precipitation in different parts of the region.

The climatological pressure systems that dominated on Middle East in winter are the Siberian high, the red sea trough, the subtropical high and the westerly trough. While the pressure systems that dominated on KSA area in summer are the Indian monsoon low, the thermal low and the subtropical high. In the second transitional season (Autumn) the pressure system that appeared and dominants are the Red sea trough, the Siberian high and the easterly trough. During winter and when the Siberian high pressure is dominated over the Middle East the temperature is coldest one. The maximum heating is associated with the location of low pressure systems. And the larger heating occurs in summer over the Indian content and the eastern part of KSA in association with the location of Indian monsoon low. The oscillation and strength of Asiatic monsoon low pressure and subtropical high pressure play an important role in rainfall over the River Nile. The annual migration of the ITCZ and seasonal development of the monsoon winds are key-components of the climatology in the Indian Ocean and the surrounding areas.

The dry and wet condition may be related with tropical easterly jet stream during weak El Nino year and enhanced in La Nina year respectively. Subtropical jet stream has affected on temperature and rainfall over Arabian Peninsula, where the core of the subtropical jet is stronger during the winter than the other seasons and located near 27.5oN, while it’s weaker during the summer and shifted north ward to appear at 43oN.The interaction between the polar front jet stream (PFJ) and subtropical jet stream (SJS) and its role in the surface cyclogenesis has been affected not only over the North African region but also over other subtropical regions. The Mediterranean climate is characterized by cold-season rainfall originating in the southward spread of the Jet stream during winter, accompanied by a southward shift of surface cyclone tracks, which developed mostly during the cold season.

AcknowledgementsThe author is grateful to the colleagues in Department of Meteorology, Faculty of Meteorology, Environment, and Arid Land Agriculture, King Abdelaziz University, Kingdom of Saudi Arabia.

GlossaryMiddle East: The Middle East is a region that spans southwestern Asia, western Asia, and

northeastern Africa.Climate change: Climate change is “any change in climate over time, whether due to natural

variability or as a result of human activity.Dust Storm: a strong hot dry wind laden with dust appears in arid and semi-arid regions.

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Subtropical High Pressure: Semi-permanent high atmospheric pressure centered, in the mean, near 30°N and 30°S latitudes and associated with the subsidence of the Hadley cell.

Siberian High Pressure: An area of high pressure which forms over Siberia in winter centered in northeastern Siberia. The anticyclone forms because of the intense cooling of the surface layers of air over the continent during this season.

El Nino: Periodic warming of central and eastern tropical Pacific waters.La Nina: Refers to the extensive cooling of the central and eastern Pacific OceanSouthern Oscillation: The pattern of reversing surface air pressure between the eastern and western

tropical Pacific; when the surface pressure is high in the eastern tropical Pacific it is low in the western tropical Pacific, and vice-versa.

El Nino Southern Oscillation (ENSO): The coupled interactions between the ocean and atmosphere that occur in the tropical Pacific, now known to link what were once thought to be the separate phenomena of El Niño and the Southern Oscillation.

Indian Monsoon Low Pressure: The first zone, extending north from latitude 10° S, has a monsoon climate (characterized by semiannual reversing winds). In the Northern Hemisphere “summer” (May–October), low atmospheric pressure over Asia and high pressure over Australia result in the southwest monsoon, with wind speeds up to 45 km per hour and a wet season in South Asia. During the northern “winter” (November–April), high pressure over Asia and low pressure from 10°S to northern Australia bring the northeast monsoon winds and a wet season for southern Indonesia and northern Australia.

North Atlantic Oscillation: Defined as the difference between the normalized mean December-March sea-level pressure anomalies at locations representative of the relative strengths of the Azores High and Icelandic Low.Subtropical jet stream: A belt of strong upper-level westerly wind, located above regions of

subtropical high pressure at the point where there is a steep temperature gradient in the upper troposphere and a major break in the height of the tropopause.

Polar front jet stream: Narrow band of very fast exists in the mid-latitudes at altitudes of 10–13 kilometers in the upper troposphere or lower stratosphere. Jet streams usually occur about the latitudes of the westerlies (35°−60°).

Tropical easterly jet: An upper level easterly wind centered around 15°N, 50-80°E and extends from South-East Asia to Africa starts in late June and continues until early September.

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Biographical SketchHosny Hasanean was born and raised in Asuot, Egypt. After high school, he joined in a

Meteorological Authority of Egypt for four years, which offered him an experience in Meteorology. He gained his Higher Diploma in Meteorology in 1987 from Cairo University. He has been hired in Department of Astronomy and Meteorology, Faculty of Science, Cairo University in 1988. He received his MS and PhD in Meteorology in 1992 and 1996 respectively. His MS research interest was “Causes

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of Climatic Change over Egypt” and PhD research interest was “Validation and evaluation of cloud parameterization roles in atmospheric radiation process". In The Department of Astronomy and Meteorology, Cairo University he has been a pointed as a Lecturer (1992-1996), Assistance Professor (1996-2003), Associate Professor (2003-2007) and Professor (2007-present). Climate and climate change have been his main research interests since graduate school. In addition to the above topics he is very interested in Middle East Meteorology which was his main research foci for years. His other research interests have been tropical-subtropical interaction and atmospheric circulation. Also he interests climatic global indices and its affect on climatic element. Recently, his research repertoire has expanded to the climate and climate change over Arabian Peninsula. In 2004, Dr. Hasanean has joined the international editorial board of The International Journal of Meteorology. Also, he works as a referee for many international journals in Meteorology. He is an associate member of The Abdu-Salam International Center for theoretical physics (ICTP) Trieste, Italy. Dr. Hasanean is currently a Professor in the Department of Meteorology, Faculty of Meteorology, Environment and Arid Land Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia.

Figure CaptionsFigure 1 The topo map of the Middle East shows the topography of the Middle Eastern countries. Map features include country names and borders plus rivers, lakes, and land features.

Figure 2: map of Egypt (http://www.climate-zone.com/climate/egypt/)

Figure 3: Map of Arabia Peninsula http://www.metmuseum.org/toah/hd/m_wap/hd_m_wap.htm)Figure 4: shows the direction and the source of the effecting air masses over the AP (Ghazanfar and Fisher, 1998). The distribution of the surface pressure over the AP during winter time is shown in the middle map while the summer time is shown in the right map (Abdullah and Al-Mazroui, 1998).

Figure 5: Location and topography of kingdom Saudi Arabia. Almazroui et al., 2009.

Figure 6: The average of the annual values of rainfall over KSA stations (Alamodi et al., 2009).

Figure 7: A) The average of the winter values of rainfall over KSA stations, B) The average of the spring values of rainfall over KSA stations (Alamodi et al., 2009).

Figure 8: A) The average of the summer values of rainfall over KSA stations, B) The average of the autumn values of rainfall over KSA stations (Alamodi et al., 2009).

Figure 9: Location of the study area (central coastal lowlands of Saudi Arabia) and the weather stations, Barth and Steinkohl, (2004).

Figure 10: map of Oman http://en.wikipedia.org/wiki/Geography_of_Oman)

Figure 11: Monthly rainfall distribution in Oman. Kwarteng, et al., 2009.

Figure 12: Relations between average yearly rainfall and elevations. Kwarteng, et al., 2009.

Figure 13:map of United Arab Emirates(http://www.climate-zone.com/climate/United Arab Emirates /)

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Figure 14: (a) Average annual rainfall and (b) monthly temperature patterns. (The United Arab Emirates, Initial National Communication to the United Nations Framework Convention on Climate Change, Ministry of Energy, http://unfccc.int/resource/docs/natc/arenc1.pdf).

Figure 15: Map of Qatar (http://en.wikipedia.org/wiki/Geography_of_qatar)

Figure 16: map of Bahrain (http://www.climate-zone.com/climate/bahrain/)

Figure 17: map of Kuwait (http://www.climate-zone.com/climate/ kuwait/)

Figure 18: map of Yemen (http://www.climate-zone.com/climate/yemen/)

Figure 19: Mean monthly rainfall (mm) at selected stations. Farquharson, et al., 1996

Figure 20: Map of Syria (http://www.climate-zone.com/climate/syria/

Figure 21: map of Lebanon (http://www.climate-zone.com/climate/lebanon/)

Figure 22: Monthly averages of air temperatures at different Lebanese locations http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf).

Figure 23: Monthly rain distribution at different Lebanese locations (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf).Figure 24: Average monthly potential evapotranspiration and rain-air temperature plotting curve (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf).

Figure 25: map of Jordan (http://www.climate-zone.com/climate/jordan/)

Figure 26: mean monthly precipitation pattern in winter (Menzel, et al., 2007).

Figure 27: Map of Israel and Plastine (http://www.climate-zone.com/climate/israel/).

Figure 28: Annual normal rainfall map of Israel, 1961-1990 (Goldreich, 1995).

Figure 29: An average vertical temperature profile for summer days and summer rain days (Saaroni and Ziv, 2000).

Figure 30: Time series of rain and drop days for July and August 1951–1997 according to all the measurement stations in Israel (Saaroni and Ziv, 2000).

Figure 31. The winter stream flow in the Jordan River and the winter Nino4 SSTs in the tropical Pacific. From Price et al. (1998).

Figure 32: map of Cyprus (http://www.climate-zone.com/climate/cyprus/)

Figure 33: Map of Iraq (http://geography.about.com/library/cia/blciraq.htm)

Figure 34: Map of Turkey (http://www.climate-zone.com/climate/turkey/).

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Figure 35: Climate classification of Turkey via Thornthwaite method (Sensoy, S. et al, 2008)

Figure 36: Seasonal rainfall distribution of Turkey (Sensoy, S. et al, 2008)

Figure 37: Climate diagram of Turkey (Sensoy, S. et al, 2008)

Figure 38: Geographical distribution of mean annual precipitation (Sensoy, S. et al, 2008)

Figure 39: The Mountain influence on Turkey precipitation (Sensoy, S., 2004)

Figure 40: Air masses affecting Turkey (Sensoy, S., 2004).

Figure 41: map of Iran (http://www.climate-zone.com/climate/iran/)

Figure 42: The spatial distribution of the Iranian mean air temperature (oC) a) winter and b) summer for the period of 1951–2000 (Ghasemi and Khalili, 2006).

Figure 43: Weather map for Middle East showing conditions for a prefrontal occurrence of dust storms (Taghavi and Asadi, 2007).

Figure 44: NOAA MODIS image from 26 March showing the deep cyclone over the northern Arabian peninsula and the dust over Iraq and much of Southwest Asia, From Grumm, 2003.Figure 45: a) Positive North Atlantic Oscillation and b) Negative Atlantic Oscillation Index (http://www.ldeo.columbia.edu/res/pi/NAO/)

Figure 46. Change in winter (December-March) surface temperature corresponding to a unit deviation of the NAO index over 1900 to 2005. The contour increment is 0.2°C. Regions of insufficient data (e.g., over much of the Arctic) are not contoured.

Figure 47. Change in winter (December-March) precipitation corresponding to a unit deviation of the NAO index over 1979-2003. The contour increment is 0.3 mm day-1.

Figure 48: a) boreal summer (Indian Summer Monsoon season) and (b) boreal winter (northeast monsoon season). Bold dashed line marks the location of the ITCZ. Bold arrow marks the location of the Findlater Jet also known as Somali Jet (adapted by Gasse, 2000).

Table CaptionsTable 1: The trend values of the annual, winter, spring, summer and autumn temperature of KSA stations extracted from NNR by Mann-Kendall rank correlation test.

Table 2a. The detected years of abrupt warming of the annual temperature of KSA stations by Mann-Kendall rank statistic test.

Table 2b. The detected years of abrupt cooling of the annual temperature of KSA stations by Mann-

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Kendall rank statistic test.

Table 3: Climatic characteristic of Yemen (http://www.un.org/esa/forests/pdf/session_documents/unff8/ statements/28%20April%20AM/Yemen.pdf).

Table 4 Monthly mean rainfall (mm) at selected stations. Farquharson, et al., 1996

Table 5: Projected climatic changes in Yemen for 2050 based OSU, ECHAM3TR and UKHI GCMs (GOY, 2001), http://unfccc.int/resource/docs/napa/yem01.pdf.

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Figure 1: The topo map of the Middle East shows the topography of the Middle Eastern countries.  Map features include country names and borders plus rivers, lakes, and land features.

Figure 2: map of Egypt (http://www.climate-zone.com/climate/egypt/)

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Figure 3: Map of Arabia Peninsula http://www.metmuseum.org/toah/hd/m_wap/hd_m_wap.htm)

Figure 4: shows the direction and the source of the effecting air masses over the AP (Ghazanfar and Fisher, 1998). The distribution of the surface pressure over the AP during winter time is shown in the middle map while the summer time is shown in the right map (Abdullah and Al-Mazroui, 1998).

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Figure 5: Location and topography of kingdom Saudi Arabia. Almazroui et al., 2009.

Figure 6: The average of the annual values of rainfall over KSA stations (Alamodi et al., 2009).

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Figure 7: A) The average of the winter values of rainfall over KSA stations, B) The average of the spring values of rainfall over KSA stations (Alamodi et al., 2009).

Figure 8: A) The average of the summer values of rainfall over KSA stations, B) The average of the autumn values of rainfall over KSA stations (Alamodi et al., 2009).

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Figure 9: Location of the study area (central coastal lowlands of Saudi Arabia) and the weather stations, Barth and Steinkohl, (2004).

Figure 10: map of Oman http://en.wikipedia.org/wiki/Geography_of_Oman)

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Figure 11: Monthly rainfall distribution in Oman. Kwarteng, et al., 2009.

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Figure 12: Relations between average yearly rainfall and elevations. Kwarteng, et al., 2009.

Figure 13: map of United Arab Emirates (http://www.climate-zone.com/climate/ United Arab Emirates /)

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Figure 14: (a) Average annual rainfall and (b) monthly temperature patterns. (The United Arab Emirates, Initial National Communication to the United Nations Framework Convention on Climate Change, Ministry of Energy, http://unfccc.int/resource/docs/natc/arenc1.pdf).

Figure 15: Map of Qatar (http://en.wikipedia.org/wiki/Geography_of_qatar)

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Figure 16: map of Bahrain (http://www.climate-zone.com/climate/bahrain/)

Figure 17: map of Kuwait (http://www.climate-zone.com/climate/ kuwait/)

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Figure 18: map of Yemen (http://www.climate-zone.com/climate/yemen/)

Figure 19: Mean monthly rainfall (mm) at selected stations. Farquharson, et al., 1996

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Figure 20: Map of Syria (http://www.climate-zone.com/climate/syria/

Figure 21: map of Lebanon (http://www.climate-zone.com/climate/lebanon/)

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Figure 22: Monthly averages of air temperatures at different Lebanese locations http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf).

Figure 23: Monthly rain distribution at different Lebanese locations (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf).

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Figure 24: Average monthly potential evapotranspiration and rain-air temperature plotting curve (http://www.fao.org/sd/climagrimed/pdf/ws01_24.pdf).

Figure 25: map of Jordan (http://www.climate-zone.com/climate/jordan/)

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Figure 26: mean monthly precipitation pattern in winter (Menzel, et al., 2007).

Figure 27: Map of Israel and Plastine (http://www.climate-zone.com/climate/israel/).

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Figure 28: Annual normal rainfall map of Israel, 1961-1990 (Goldreich, 1995).

Figure 29: An average vertical temperature profile for summer days and summer rain days (Saaroni and Ziv, 2000).

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Figure 30: Time series of rain and drop days for July and August 1951–1997 according to all the measurement stations in Israel (Saaroni and Ziv, 2000).

Figure 31. The winter stream flow in the Jordan River and the winter Nino4 SSTs in the tropical Pacific. From Price et al. (1998).

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Figure 32: map of Cyprus (http://www.climate-zone.com/climate/cyprus/)

Figure 33: Map of Iraq (http://geography.about.com/library/cia/blciraq.htm)

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Figure 34: Map of Turkey (http://www.climate-zone.com/climate/turkey/).

Figure 35: Climate classification of Turkey via Thornthwaite method (Sensoy, S. et al, 2008)

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Figure 36: Seasonal rainfall distribution of Turkey (Sensoy, S. et al, 2008)

Figure 37: Climate diagram of Turkey (Sensoy, S. et al, 2008)

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Figure 38: Geographical distribution of mean annual precipitation (Sensoy, S. et al, 2008)

Figure 39: The Mountain influence on Turkey precipitation (Sensoy, S., 2004)

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Figure 40: Air masses affecting Turkey (Sensoy, S., 2004).

Figure 41: map of Iran (http://www.climate-zone.com/climate/iran/)

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Figure 42: The spatial distribution of the Iranian mean air temperature (oC) a) winter and b) summer for the period of 1951–2000 (Ghasemi and Khalili, 2006).

Figure 43: Weather map for Middle East showing conditions for a prefrontal occurrence of dust storms (Taghavi and Asadi, 2007).

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Figure 44: NOAA MODIS image from 26 March showing the deep cyclone over the northern Arabian peninsula and the dust over Iraq and much of Southwest Asia, From Grumm, 2003.

Figure 45: a) Positive North Atlantic Oscillation and b) Negative Atlantic Oscillation Index (http://www.ldeo.columbia.edu/res/pi/NAO/)

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Figure 46. Change in winter (December-March) surface temperature corresponding to a unit deviation of the NAO index over 1900 to 2005. The contour increment is 0.2°C. Regions of insufficient data (e.g., over much of the Arctic) are not contoured.

Figure 47. Change in winter (December-March) precipitation corresponding to a unit deviation of the NAO index over 1979-2003. The contour increment is 0.3 mm day-1.

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Figure 48: a) boreal summer (Indian Summer Monsoon season) and (b) boreal winter (northeast monsoon season). Bold dashed line marks the location of the ITCZ. Bold arrow marks the location of the Findlater Jet also known as Somali Jet (adapted by Gasse, 2000).

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Table 1: The trend values of the annual, winter, spring, summer and autumn temperature of KSA stations extracted from NNR by Mann-Kendall rank correlation test.

Station Long Lat TrendAnnual Win Spr Sum Aut

Turaif 38.74 31.69 -0.025 -0.03 0.049 0.148 -0.044

Guriat 37.28 31.41 -0.039 0.048 0.074 0.022 -0.074Arar 41.14 30.90 0.079 0.016 0.159 0.201 -0.122

Aljouf 40.99 29.79 -0.049 -0.074 0.005 0.192 -0.005Rafha 43.49 29.62 0.074 -0.049 0.059 0.286 0.01

Tabouk 36.61 28.38 -0.030 -0.03 -0.044 0.182 0.049Alqaisoma 46.13 28.32 0.167 0.025 0.167 0.374 0.128

Hail 41.69 27.43 0.189 0.048 0.120 0.399 0.141Gassim 43.77 26.31 0.034 -0.044 -0.099 0.325 0.079Dhahran 50.16 26.26 0.345 0.204 0.231 0.399 0.423Alwajh 38.48 26.21 0.074 -0.069 -0.03 0.369 0.167Alahsa 49.49 25.30 0.342 0.307 0.307 0.368 0.238

Riyadh new 46.72 24.93 0.212 0.221 0.177 0.299 0.013Riyadh Old 46.74 24.71 0.300 0.093 0.159 0.468 0.348

Madinah 39.70 24.55 0.438 0.213 0.246 0.586 0.408Yanbo 38.06 24.14 0.310 0.079 0.000 0.468 0.438Jeddah 39.19 21.71 0.571 0.354 0.303 0.613 0.577

Taif 40.55 21.48 0.571 0.366 0.318 0.640 0.568Makkah 39.77 21.44 0.489 0.325 0.29 0.446 0.394Albaha 41.64 20.29 0.472 0.455 0.255 0.463 0.489Bisha 42.62 19.99 0.652 0.42 0.333 0.67 0.655

Khamis Moshet 42.81 18.30 0.667 0.411 0.387 0.625 0.676Abha 42.66 18.23 0.547 0.355 0.261 0.502 0.606

Najran 44.41 17.61 0.419 0.246 0.236 0.207 0.409

Sharorah 47.11 17.47 0.247 0.065 0.126 0.082 0.333Gizan 42.58 16.90 0.652 0.423 0.39 0.592 0.643

Table 2a. The detected years of abrupt warming of the annual temperature of KSA stations by Mann-Kendall rank statistic test.

years Stations1986 Turaif – Gizan1987 Aljouf

1996 Turaif – Rafha1998 Tabouk – Bisha

2000 Turaif – Rafha – Alqaisoma – Ahsa – Riyadh new – Makkah – Bisha2003 Tabouk

Table 2b. The detected years of abrupt cooling of the annual temperature of KSA stations by Mann-Kendall rank statistic test.

years Stations1983 Turaif – Aljouf – Gizan1988 Guriat

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1994 Alqaisoma – Ahsa1997 Riyadh new – Makkah – Sharurah

Table 3: Climatic characteristic of Yemen (http://www.un.org/esa/forests/pdf/session_documents / unff8/statements/28%20April%20AM/Yemen.pdf)

Table 4 Monthly mean rainfall (mm) at selected stations. Farquharson, et al., 1996

Table 5: Projected climatic changes in Yemen for 2050 based OSU, ECHAM3TR and UKHI GCMs (GOY, 2001), http://unfccc.int/resource/docs/napa/yem01.pdf.

Climate element Minimum Maximum

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Temperature change (oC) 1.4 2.8Precipitation change (%) -24 35Cloud cover change (%) -6 18

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