Weather and Climate

Weather and ClimateLecture IILayers of the AtmosphereTroposphereStratosphereMesosphereThermosphereExosphereTroposphereIt is the lowest layer of the atmosphere.Almost all weather occurs in this layer and this is the layer where planes usually fly.Starts at Earths surface and is around 20km high.The temperature is about 17C

StratosphereThe second layer of the atmosphere is the stratosphere.The stratosphere is very dry and so doesnt contain many clouds.The stratosphere extends around 50km down to anywhere from 6-20km above the Earth surfaceThe temperature is about -15C at the top of the stratosphere.MesosphereThis is the third layer of the atmosphere.Here different gases mix together and meteors vapourise.This layer extends from about 50km to 85km above the earths surface.The temperature is about -90C.

ThermosphereThis is the fourth layer of atmosphere.Space shuttles orbit in this layer.It is about 90km to 5,000km above our planet.Temperatures can reach 500C.

ExosphereThis the last layer of our atmosphere.Here atoms and molecules are released into space.It is over 5,000km above our planet.The temperature can reach thousands of Celsius.Chemical CompositionThe Earths atmosphere is a complex mixture of gases: nitrogen (N2) (about 78% by volume), oxygen (O2) (about 21% by volume) and argon (Ar) (about 0.9% by volume) with small and varying amounts of water vapor (H2O) (0 to 4% by volume) and still smaller amounts of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3) and dozens of other gases at still smaller concentrationsChemical CompositionThe protection afforded by the atmosphere is very important for life on Earth. The atmosphere shields the Earths surface and its myriad forms of life from biologically damaging high-energy cosmic radiation. In addition, ozone, found mostly in the stratosphere, absorbs ultraviolet radiation from the Sun, shielding the Earths surface from this biologically damaging radiation.

What is Weather + ClimateWeather is the hour-by-hour, day-by-day conditions of the atmosphere.Climate is the the average weather conditions over a long period of time.Factors affecting WeatherTemperature PrecipitationAir pressureWind speed and directionSunshineHumidityCloud Cover

TemperatureTemperature is measured in degrees centigrade by a maximum and minimum thermometer. During the day, the mercury or alcohol expands and in the night the mercury or alcohol contracts.

Temperature is measured in degrees centigrade by a maximum and minimum thermometer. During the day, the mercury or alcohol expands, pushing the metal pin higher on the scale. In the night the mercury or alcohol contracts.

14PrecipitationRainfall (a type of precipitation) is measured in mm by a rain gauge. The water collected can be poured into a measuring cylinder and then can be recorded.

15Air PressureAir pressure is measured in millibars (mb) on a barometer. As the pressure changes the cylinder rises causing the lever to move and the pen to draw on the rotating drum.

Wind SpeedWind speed is measured in miles per hour or knots and is measured using an anemometer. A wind meter can also be used.

Wind DirectionWind direction is measured by a wind vane which turns in the direction the wind is coming from. Most of Britains winds come from the south-west. These are called prevailing winds.

SunshineSunshine is measured using a Campbell Stokes sunshine recorder. A note is made of how much sunshine there is everyday.

Sunshine

HumidityHumidity is measured by a hygrometer in milliliters per cubic centimeters. However some hygrometers measure humidity in percentages.

Effects of HumidityAnimals and plants Humidity is one of the fundamentalabiotic factorsthat defines any habitat, and is a determinant of which animals and plants can thrive in a given environment.

Human comfort Humans are sensitive to humid air because the human body uses evaporative cooling as the primary mechanism to regulate temperature.

Effects of HumidityElectronics Many electronic devices have humidity specifications, for example, 5% to 95%. At the top end of the range, moisture may increase the conductivity of permeableinsulatorsleading to malfunction.

Building construction Traditional building designs typically had weakinsulation, and it allowed air moisture to flow freely between the interior and exterior

Cloud CoverCloud cover is measured in oktas. Each okta represents one-eighth of the sky covered by cloud.

Stevenson ScreenA Stevenson Screen is a store where weather instruments are kept. It is white to reflect sunlight and slatted to allow air to circulate. It is placed on grass away from buildings and trees.

Types of CloudsCumulus, Stratus and StratocumulusAltocumulus and AltostratusCirrocumulus, Cirrus, Cirrostratus and CumulonimbusThe lowest cloudsThe lowest clouds in the atmosphere are stratus, cumulus and stratocumulus. These clouds are around 6,000 feet high. Stratus clouds are horizontal layers and cumulus clouds are cotton-like in appearance. Stratocumulus is a cross between them.

Mid-Level CloudsMid-level clouds include altocumulus and altostratus. Theses clouds range from 6,000 feet to 20,000 feet. Altocumulus clouds are dark individual segments. Altostratus clouds are thin sheets from which the sun can be seen through.

The Highest CloudsThe highest clouds are cirrus, cirrocumulus, cirrostratus and cumulonimbus. They are around 20,000 feet high. Cirrus clouds look like thin wispy stripes, cirrocumulus clouds look like fish scales, cirrostratus clouds look like white veils and cumulonimbus clouds are very tall, large clouds.

The Water CycleThe sun causes water to form water vapour and rise up into the atmosphere. i.e. evaporation.At the same time transpiration (the transfer of water from trees into the atmosphere) occurs.As water vapour rises it begins to cool. The temperature falls by 1C for every 100m you ascend. At the dew point the water vapour cools to form clouds.Soon the water droplets become heavy and fall as precipitation.Factors Affecting UKs ClimateLatitudeThe Gulf StreamSouth-westerly Prevailing WindsAltitudeDistance from the SeaLatitude The higher the latitude, the colder it will be as the Suns rays have to travel further through the atmosphere to reach areas of higher latitude like Britain.

The Gulf StreamThe Gulf Stream (North Atlantic Drift) is a water current from the Gulf of Mexico that brings moist warm air across the Atlantic Ocean to the west of the British Isles.

SW Prevailing WindsThe south-westerly prevailing winds are the UKs most common winds which travel across the Atlantic Ocean picking up lots of moisture which then gets dropped on the first land mass it meets - Britain.AltitudeThe higher the altitude, the colder it is. Higher areas like Lake District receive more rainfall because air is forced to rise upwards and the water vapour condenses to form clouds.

35Distance to SeaOceans heat up and cool down much more slowly than land. This means that coastal locations tend to be cooler in summer and warmer in winter than places inland which are at the same latitudes and altitudes.MicroclimatesShelterSurfaceAspectNatural Physical FeaturesBuildings

ShelterBuildings, walls, hills and valleys can provide shelter. It will feel a degree or two warmer on the sheltered side than the side facing the wind.

This side of the hedge is warmer.This side is colder as it is facing the wind.SurfaceDark surfaces absorb heat and are therefore warmer than light shiny surfaces. Light surfaces reflect heat and are therefore cooler.Light surface reflects heat

Dark surfaces absorb heatAspectAs the sun moves through the sky, it warm slopes that face it. In Britain, south-facing slopes receive more sunlight than north-facing slopes as the sun moves through the south during the day.

This slope is warmerBuildingsDuring the day, dark buildings absorb heat and release it in the night. Buildings also break up the wind depending on the direction they are facing and the prevailing wind direction.

Buildings absorb heat.Natural Physical FeaturesRain is caught in the canopy of a forest, reducing precipitation. In winter, it feels warmer in a sheltered forest as the trees provide protection from the cooling wind. In summer it feels cooler as the trees block out the sun.

Warmer in winter and colder in summerPressure SystemsAnticyclonesDepressionsAnticyclonesAnticyclonesProcessCool air sinkingAir MassesOne air mass at time.Isobars on MapIsobars dispersedWeatherStill or very light windsSeasonal VariationVery cold in winter; hot in summerPressureHigh PressureDepressionsDepressionProcessWarm air risingAir MassesTwo air massesIsobars on MapIsobars tightly packedWeatherWind, cloudy skiesSeasonal VariationWet, mild and windy throughout the year.PressureLow pressureTypes of RainfallRelief RainfallConvectional RainfallFrontal Rainfall.Relief RainfallPrevailing winds bring moist air to Britain.Air is forced to rise over high areas.Air cools and condensesClouds form and it starts to rain.Air descends on the other side of the mountain.It warms up and dries over an area to the east of the mountains known as the rain shadow.Relief Rainfall Diagram

Convectional RainfallThe sun heats the earth.The earth heats the air above it.Hot air rises because it is less dense.The water vapour cools at the dew point and condenses into water droplets.These water droplets join together and then fall as rain.

Convectional Rainfall Diagram

Frontal RainfallWhen a warm and cold air mass meet they dont mix.The lighter warmer air rises over the heavier, colder air.As the warm air rises condensation occurs, clouds form and rain falls along the front.First a warm front passes over, bringing rain and warm air, then a cold front passes bringing more rain and cold air.Frontal Rainfall Diagram