The climate of India is strongly The climate of India is strongly influenced by monsoon winds. influenced by monsoon winds. The monsoons are experienced in the The monsoons are experienced in the tropical area between 20 tropical area between 20 º º N to 20 N to 20 º º S. S. Let us understand the following facts: Let us understand the following facts: 1. The differential heating and cooling of 1. The differential heating and cooling of land and water. land and water. 2. The shift of the position of Inter 2. The shift of the position of Inter Tropical Convergence Zone. (ITCZ)- The Tropical Convergence Zone. (ITCZ)- The equatorial trough (monsoon trough) from equatorial trough (monsoon trough) from 5 5 º N shifts to Ganga Plain in summer. º N shifts to Ganga Plain in summer.
Transcript
The climate of India is strongly influenced by The climate of India is strongly influenced by monsoon winds.monsoon winds.
The monsoons are experienced in the tropical The monsoons are experienced in the tropical area between 20area between 20ºº N to 20 N to 20º º S.S.
Let us understand the following facts:Let us understand the following facts: 1. The differential heating and cooling of land and 1. The differential heating and cooling of land and
water.water. 2. The shift of the position of Inter Tropical 2. The shift of the position of Inter Tropical
Convergence Zone. (ITCZ)- The equatorial trough Convergence Zone. (ITCZ)- The equatorial trough (monsoon trough) from 5(monsoon trough) from 5º N shifts to Ganga Plain º N shifts to Ganga Plain in summer.in summer.
3. The presence of the high pressure area, east 3. The presence of the high pressure area, east of Madagascar. (approx. at 20of Madagascar. (approx. at 20º over the º over the Indian ocean.) The intensity and position of Indian ocean.) The intensity and position of the this high pressure effects the IMthe this high pressure effects the IM
4.The Tibetan plateau gets intensely heated 4.The Tibetan plateau gets intensely heated during summer and which results in strong during summer and which results in strong vertical air currents and low pressure at 8 km vertical air currents and low pressure at 8 km above the sea level. above the sea level.
5. The movement of westerly jet stream to the 5. The movement of westerly jet stream to the north of Himalayas and the presence of north of Himalayas and the presence of tropical easterly jet stream over the Indian tropical easterly jet stream over the Indian Peninsula. Peninsula.
1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds
Middle-latitude desertsMiddle-latitude deserts
exist in rain shadows.
1) Deserts: where & why1) Deserts: where & whyDeserts & windsDeserts & winds
SOUTHERN OSCILLATION SOUTHERN OSCILLATION
Changes in the pressure conditions over the Changes in the pressure conditions over the southern ocean also affect the monsoon.southern ocean also affect the monsoon.
Normal condition- The tropical eastern Normal condition- The tropical eastern south Pacific ocean experiences high south Pacific ocean experiences high pressure and the tropical eastern Indian pressure and the tropical eastern Indian ocean experience low pressure. ocean experience low pressure.
But in certain years there is a reversal in But in certain years there is a reversal in the above condition. This periodic change is the above condition. This periodic change is known as SO.known as SO.
EL NINOEL NINO
EL NINO EVENT connected to SO- EL NINO EVENT connected to SO- During which a warm ocean current During which a warm ocean current that flows past the Peruvian Coast, in that flows past the Peruvian Coast, in place of the cold Peruvian current, place of the cold Peruvian current, every 2 to 5 years. The changes in every 2 to 5 years. The changes in pressure conditions are connected to pressure conditions are connected to the El Nino.the El Nino.
HOW TO PREDICT THE HOW TO PREDICT THE INTENSITY OF MONSOONINTENSITY OF MONSOON
The difference in pressure over Tahiti The difference in pressure over Tahiti and Darwin in north Australia (Pacific and Darwin in north Australia (Pacific ocean, 18ocean, 18º S/149º W and Indian º S/149º W and Indian Ocean 12º30Ocean 12º30’’S/131ºE) is computed.S/131ºE) is computed.
If the pressure difference were If the pressure difference were negative, it would mean below negative, it would mean below average and late monsoon.average and late monsoon.
The onset of monsoonThe onset of monsoonMonsoon winds are affected by different Monsoon winds are affected by different
atmospheric conditions.atmospheric conditions. In May- summer month, the temperature In May- summer month, the temperature
rises- low pressure trough is developed. In rises- low pressure trough is developed. In June this trough attracts south-east trade June this trough attracts south-east trade winds from the south of equator. These winds from the south of equator. These moisture carrying winds deflect right in moisture carrying winds deflect right in lands and known as south-westerly winds. lands and known as south-westerly winds.
These strong winds overrun the whole These strong winds overrun the whole country in a months time.country in a months time.
DIVISION OF MONSOON WINDS DIVISION OF MONSOON WINDS BY PENINSULA BY PENINSULA
THE ARABIAN SEA BRANCHTHE ARABIAN SEA BRANCH It enters Kerela till 1It enters Kerela till 1stst June. June. It reaches Mumbai till 10It reaches Mumbai till 10thth June. June. It arrives over Saurashtra-Kuchchh and central India till It arrives over Saurashtra-Kuchchh and central India till
Mid JuneMid June
THE BAY OF BENGAL BRACHTHE BAY OF BENGAL BRACH It advances rapidly and reaches in Assam in the 1It advances rapidly and reaches in Assam in the 1stst
week of June. week of June. It turns to Ganga Plain because of Mountain rangeIt turns to Ganga Plain because of Mountain range It causes rain in Delhi till 29It causes rain in Delhi till 29thth June and in Punjab till 5 June and in Punjab till 5thth
July.July.
Merging of branchesMerging of branches
Both the branches merge over north-Both the branches merge over north-western part of Ganga Plain.western part of Ganga Plain.
In the western Himalayas ( Himachal In the western Himalayas ( Himachal Pradesh) They cause heavy rainfall.Pradesh) They cause heavy rainfall.
The islands receive the very first The islands receive the very first monsoon from south to north from the monsoon from south to north from the 11stst week of April to 1 week of April to 1stst week of May. week of May.
WITHDRAWAL OF MONSOONWITHDRAWAL OF MONSOON
It begins in north-western states by early It begins in north-western states by early sep. sep.
It withdraws completely from the northern It withdraws completely from the northern half of peninsula till mid oct. in slow pace.half of peninsula till mid oct. in slow pace.
It withdraws from southern part rapidly.It withdraws from southern part rapidly. By early Dec. Withdrawal is completed.By early Dec. Withdrawal is completed. From the islands withdrawal takes place From the islands withdrawal takes place
from 1from 1stst week of Dec. to 1 week of Dec. to 1stst week of Jan week of Jan from north to south direction.from north to south direction.
THE SEASONSTHE SEASONSTHE COLD WINTER SEASONTHE COLD WINTER SEASON
Northern India ( Mid Nov. to Feb.)Northern India ( Mid Nov. to Feb.) Dec. and Jan. coldest monthsDec. and Jan. coldest months Normal tem. 10Normal tem. 10º to 15ºCº to 15ºC Days are warmer than nightsDays are warmer than nights Frost in common in north and snowfall Frost in common in north and snowfall
in Himalayas in Himalayas The northern trade winds prevail over The northern trade winds prevail over
country. They do not cause rain in north country. They do not cause rain in north india.(Land to sea)india.(Land to sea)
NORTHERN INDIANORTHERN INDIA
In northern india high pressure regions In northern india high pressure regions develops and with light winds moving develops and with light winds moving outwards from this area.outwards from this area.
Because of relief these winds blow through Because of relief these winds blow through Ganga valley from west to the northwest.Ganga valley from west to the northwest.
Clear sky, low temp., and variable winds.Clear sky, low temp., and variable winds. Rain fall- The two parts of india get rainfall.Rain fall- The two parts of india get rainfall. 1. North-west part of india- from the 1. North-west part of india- from the
Mediterranean cyclones.Mediterranean cyclones. 2.Tamil Nadu- north-east winds which blow 2.Tamil Nadu- north-east winds which blow
over the Bay of Begal. over the Bay of Begal.
SOUTHERN INDIASOUTHERN INDIA
Average Tem- 24Average Tem- 24º-25º-25 Temperature decrease from south to Temperature decrease from south to
north.north. The peninsula region does not have The peninsula region does not have
well defined cold season due to well defined cold season due to moderating influence of the sea.moderating influence of the sea.
THE HOT WEATHER SEASONTHE HOT WEATHER SEASONmarch to maymarch to may
Heat belt shifts from south to north- due to Heat belt shifts from south to north- due to the apparent movement of sun.the apparent movement of sun.
In March, April and May the highest temp. In March, April and May the highest temp. occur in The Deccan (38occur in The Deccan (38ºC), Gujarat (42ºC) ºC), Gujarat (42ºC) and North-west of India(45ºC).and North-west of India(45ºC).
In may rising temp. leads to a low In may rising temp. leads to a low pressure in a wider area from Thar Desert pressure in a wider area from Thar Desert to Chhota Nagpur.to Chhota Nagpur.
Due to low pressure, the moisture-laden Due to low pressure, the moisture-laden winds from the Arabian Sea are attracted winds from the Arabian Sea are attracted towards this area.towards this area.
Consequently there is (about 158cm) rainfall Consequently there is (about 158cm) rainfall in the Raj Mahal and Chhota Nagpur hills lying in the Raj Mahal and Chhota Nagpur hills lying between the Satpuras and the Vindhyas.between the Satpuras and the Vindhyas.
Kerala and Karnataka also experience the pre-Kerala and Karnataka also experience the pre-monsoon showers. They help in early ripening monsoon showers. They help in early ripening of mangoes- so also known as Mango showersof mangoes- so also known as Mango showers
In Peninsula temp. remains lower due to the In Peninsula temp. remains lower due to the moderating influence of oceans.moderating influence of oceans.
Other Climatic FeaturesOther Climatic Features
1. Loo- Strong, gusty, hot and dry winds 1. Loo- Strong, gusty, hot and dry winds blowing over north and north-west during blowing over north and north-west during the day (Sometimes until late in the the day (Sometimes until late in the evening).evening).
2. Dust storms-In may in north.2. Dust storms-In may in north. They bring temporary relief rain and cool They bring temporary relief rain and cool
torrential downpour with hails.-In west torrential downpour with hails.-In west Bengal these are known as Kaal Baisakhi. Bengal these are known as Kaal Baisakhi.
ADVANCING MONSOONADVANCING MONSOONRAINY SEASONRAINY SEASON
In June the low pressure in north In June the low pressure in north intensifies. It attracts the south-west trade intensifies. It attracts the south-west trade winds from subtropical areas of southern winds from subtropical areas of southern oceans(Southern hemisphere). They cross oceans(Southern hemisphere). They cross the equator and blow in a south-west and the equator and blow in a south-west and enter in Indian Peninsula.enter in Indian Peninsula.
They move from sea to land so bring They move from sea to land so bring abundant moisture. abundant moisture.
Speed- 30km/hSpeed- 30km/h
Break or BurstBreak or Burst
Early in the season, the windward side of Early in the season, the windward side of western Ghats receives more than 250cm western Ghats receives more than 250cm rainfall but decrease when it goes further.rainfall but decrease when it goes further.
The Deccan Plateau and MP get less rainfall The Deccan Plateau and MP get less rainfall because they are in the rain shadow area.because they are in the rain shadow area.
Other branch cause rainfall in north-east Other branch cause rainfall in north-east (Mawsynram) in Khasi range get heighest (Mawsynram) in Khasi range get heighest rainfall.rainfall.
Rainfall in Ganga valley decreases from Rainfall in Ganga valley decreases from east to west. So Gujarat and Rajasthan get east to west. So Gujarat and Rajasthan get scanty rainfall.scanty rainfall.
DRY SPELL OR BREAKSDRY SPELL OR BREAKS
Monsoon has wet and dry spells.Monsoon has wet and dry spells. Monsoon rains take place only few days at Monsoon rains take place only few days at
a time. a time. These breaks in monsoon are related to These breaks in monsoon are related to
the movement of monsoon trough and its the movement of monsoon trough and its axis keep on moving northward or axis keep on moving northward or southward. It determines the spatial southward. It determines the spatial distribution of rainfall.distribution of rainfall.
DIFFERENTIAL RAINFALLDIFFERENTIAL RAINFALL
Whenever the axis moves to Himalaya, It Whenever the axis moves to Himalaya, It gets heavy rainfall and the plains are dry gets heavy rainfall and the plains are dry and visa versa.and visa versa.
Heavy rainfall brings devastating flood.Heavy rainfall brings devastating flood. The frequency and intensity of tropical The frequency and intensity of tropical
depressions form at the head of Bay of depressions form at the head of Bay of Bengal and cross over to mainland.Bengal and cross over to mainland.
The depression follow the axis of the The depression follow the axis of the monsoon trough of low pressure.monsoon trough of low pressure.
(Effects of rainfall)(Effects of rainfall)
RETREATING MONSOONSRETREATING MONSOONS(Transition or Autumn Season)(Transition or Autumn Season)From hot rainy to dry winter From hot rainy to dry winter
During Oct.-Nov. with the apparent During Oct.-Nov. with the apparent movement of the sun towards the movement of the sun towards the south, the low pressure trough become south, the low pressure trough become weaker.weaker.
This is gradually replaced by high This is gradually replaced by high pressure.pressure.
The south-west monsoon winds weaken The south-west monsoon winds weaken and start withdrawing gradually. and start withdrawing gradually.
Weather phenomenaWeather phenomena
Clear sky and rise in temp.Clear sky and rise in temp. Days are warm, nights are cool and pleasant. Days are warm, nights are cool and pleasant.
Land is still moist.Land is still moist. Oct. heat is present because of rise in temp. Oct. heat is present because of rise in temp.
and humidity.and humidity. In northern india temp. starts falling in mid In northern india temp. starts falling in mid
oct.oct. Low pressure over north-west part starts Low pressure over north-west part starts
shifting towards Bay of Bengal and create shifting towards Bay of Bengal and create cyclonic disturbances over the Andaman sea.cyclonic disturbances over the Andaman sea.
Rain fall Rain fall
These cyclones cross the eastern coast These cyclones cross the eastern coast and cause heavy and widespread rainfall.and cause heavy and widespread rainfall.
They are often destructive. They struck They are often destructive. They struck the deltas of krishna, Godavari and the deltas of krishna, Godavari and Kaveri.Kaveri.
Sometime in Orissa, West Bengal and Sometime in Orissa, West Bengal and Bangladesh.Bangladesh.
The Coromonadel coast is derived from The Coromonadel coast is derived from depression and cyclones.depression and cyclones.
DISTRIBUTION OF RAINFALLDISTRIBUTION OF RAINFALL
Regions of heavy rainfall(Over 200 cm Regions of heavy rainfall(Over 200 cm rianfall - Western slopes of Western Ghats, rianfall - Western slopes of Western Ghats, West Coastal Plain, hills of Meghalaya. West Coastal Plain, hills of Meghalaya. Highest rainfall in Mawsynram above Highest rainfall in Mawsynram above 1000cm. 1000cm.
Regions of Moderate Rainfall-(100-200cm)Regions of Moderate Rainfall-(100-200cm)
Area adjoining to western ghats, Brahmaputra Area adjoining to western ghats, Brahmaputra valley, Orissa, Bihar, Jharkhand, Chhatisgarh, valley, Orissa, Bihar, Jharkhand, Chhatisgarh, MP, some parts of UP, HP, J & K, etc.MP, some parts of UP, HP, J & K, etc.
DISTRIBUTION OF RAINFALLDISTRIBUTION OF RAINFALL
Regions of Low rainfall (50-100cm) Regions of Low rainfall (50-100cm) Upper ganga valley, parts of Punjab, Upper ganga valley, parts of Punjab, Haryana, J & K, Andhara Pradesh and Haryana, J & K, Andhara Pradesh and Tamil Nadu.Tamil Nadu.
Regions of Scanty rainfall (less than Regions of Scanty rainfall (less than 50cm annual rainfall)-Kutch, Leh in 50cm annual rainfall)-Kutch, Leh in Kashmir, Western Rajasthan. Some Kashmir, Western Rajasthan. Some parts of punjab and Haryana.parts of punjab and Haryana.
CAUSES OF UNEVEN CAUSES OF UNEVEN DISTRIBUTIONDISTRIBUTION
1. Hilly and forest area get heavy rainfall because 1. Hilly and forest area get heavy rainfall because of high altitude and abundance of trees.of high altitude and abundance of trees.
2. The areas without mountains to check rain 2. The areas without mountains to check rain bearing winds get scanty rainfall. As in Rajasthan, bearing winds get scanty rainfall. As in Rajasthan, the Aravalli Hills standing parallel to the the Aravalli Hills standing parallel to the monsoon.monsoon.
3. Areas which come in the rain shadow like 3. Areas which come in the rain shadow like western side of western ghats or Ladakh.western side of western ghats or Ladakh.
4. The areas which come first in the way of rain 4. The areas which come first in the way of rain bearing winds get more as compared to areas bearing winds get more as compared to areas which come last of all. As Kolkata gets more rain which come last of all. As Kolkata gets more rain than Delhi.than Delhi.
