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Air, Weather, and ClimateAir, Weather, and Climate

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Earth’s AtmosphereEarth’s Atmosphere

Compared to the size of the Earth (12000 km), the atmosphere is Compared to the size of the Earth (12000 km), the atmosphere is a thin shell (120 km)a thin shell (120 km)Composed of:Composed of:

– ~78% N~78% N22 gas gas

– 21% O21% O22 gas gas

– 1% argon gas and other permanent gases1% argon gas and other permanent gases

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If the Earth is If the Earth is compared to compared to

thisthis Orange… Orange…the Earth’s the Earth’s atmosphere atmosphere would be would be

thinner than thinner than the layer of the layer of pesticide onpesticide on

this Orange’s this Orange’s surfacesurface

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Layers of the AtmosphereLayers of the Atmosphere

TroposphereTroposphere StratosphereStratosphere MesosphereMesosphere ThermosphereThermosphere IonosphereIonosphere ExosphereExosphere

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TroposphereTroposphere

Closest to the earth’s surfaceClosest to the earth’s surface Where we liveWhere we live

– Weather occurs hereWeather occurs here very thin (averaging 11 km or 7 miles high)very thin (averaging 11 km or 7 miles high) Contains 75% of mass most from water vaporContains 75% of mass most from water vapor Temp decreases as altitude increasesTemp decreases as altitude increases

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StratosphereStratosphere

Above the troposphereAbove the troposphere extends to 50 kilometers (31 miles) highextends to 50 kilometers (31 miles) high dry and less densedry and less dense Warmer temps higher up and cooler layers Warmer temps higher up and cooler layers

farther down, due to the absorption of uv raysfarther down, due to the absorption of uv rays Ozone layerOzone layer

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MesosphereMesosphere

extends to 85 kilometers (53 miles) highextends to 85 kilometers (53 miles) high extremely low air pressureextremely low air pressure temperature decrease with altitude reaching temperature decrease with altitude reaching

-90-90°°C at the topC at the top

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ThermosphereThermosphere

extends to 600 kilometers (372 miles) highextends to 600 kilometers (372 miles) high temperatures go up as altitude increases due to temperatures go up as altitude increases due to

absorption of solar radiation by oxygenabsorption of solar radiation by oxygen molecules so few and far between that they molecules so few and far between that they

collide rarelycollide rarely Farthest away from earth’s surfaceFarthest away from earth’s surface

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IonosphereIonosphere

when solar energy is absorbed directly by air when solar energy is absorbed directly by air molecules, the atoms gain or lose electrons and molecules, the atoms gain or lose electrons and become charged particles called ionsbecome charged particles called ions

reflects many types of radio waves allowing reflects many types of radio waves allowing them to bounce around the worldthem to bounce around the world

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ExosphereExosphere

Top of the thermosphere and continues until it Top of the thermosphere and continues until it merges with interplanetary gases, or space (372 merges with interplanetary gases, or space (372 to 6200 miles)to 6200 miles)

H and He are the primary componentsH and He are the primary components

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WeatherWeather

Contribute to WeatherContribute to Weather– Air temperature Air temperature

– Air pressure Air pressure

– Humidity Humidity

– Cloud cover Cloud cover

– Precipitation Precipitation

– Winds Winds

Types of WeatherTypes of Weather– FrontsFronts

– Severe WeatherSevere Weather

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Air TemperatureAir Temperature As solar energy reaches the equator, regions heat As solar energy reaches the equator, regions heat

up more than the poles. up more than the poles. Warm air and water at the equator travel toward Warm air and water at the equator travel toward

the poles while cold air and water at the poles the poles while cold air and water at the poles travel toward the equator in an attempt to travel toward the equator in an attempt to equalize the temperature equalize the temperature – Constant struggle = changing weather Constant struggle = changing weather

13http://www.usatoday.com/weather/tg/wglobale/wglobale.htm

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Air PressureAir Pressure Caused by the weight of air pressing down on the EarthCaused by the weight of air pressing down on the Earth

High pressure-cool, dense air that descends towards High pressure-cool, dense air that descends towards surface of earthsurface of earth– Fair weatherFair weather

Low pressure-less dense warm air goes toward the Low pressure-less dense warm air goes toward the center of a low pressure air masscenter of a low pressure air mass– Produces cloudy and stormy weatherProduces cloudy and stormy weather

Air pressure changes with weatherAir pressure changes with weather

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Humidity and Cloud CoverHumidity and Cloud Cover

Relative humidity-Relative humidity-amount of water vapor in the air amount of water vapor in the air Cloud CoverCloud Cover

– clouds cool the planet by reflecting sunlight back clouds cool the planet by reflecting sunlight back into space.into space. AlbedoAlbedo

– reduces the amount of heat that radiates into space reduces the amount of heat that radiates into space

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WindsWinds

Horizontal wind moves from areas of high to Horizontal wind moves from areas of high to low pressure low pressure

Vertical wind moves from low to high pressureVertical wind moves from low to high pressure Speed is determined by differences in pressureSpeed is determined by differences in pressure Coriolis effect Coriolis effect

– As air moves from high to low pressure in the N. As air moves from high to low pressure in the N. hemisphere, it is deflected to the right hemisphere, it is deflected to the right

– Opposite for S. hemisphereOpposite for S. hemisphere

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Winds cont.Winds cont.

Hadley cellsHadley cells– Carries heat and moisture from the tropics to the Carries heat and moisture from the tropics to the

northern and southern mid-latitudesnorthern and southern mid-latitudes Rising air motion near the equatorRising air motion near the equator Descending air motion in the subtropicsDescending air motion in the subtropics

– Lost most of water vaporLost most of water vapor

– Where deserts are locatedWhere deserts are located

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Convection CurrentsConvection Currents

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WeatherWeather WeatherWeather – daily temperature and moisture – daily temperature and moisture

conditions in a placeconditions in a place– driven by atmospheredriven by atmosphere– atmospheric conditions over short time periods (hours atmospheric conditions over short time periods (hours

or days) in small geographic areasor days) in small geographic areas– produced by interacting air massesproduced by interacting air masses– Types of weatherTypes of weather

Warm Front-warmWarm Front-warm air displaces cool airair displaces cool air Cold Front-cooler air displaces warmer air Cold Front-cooler air displaces warmer air Severe-hurricanes, thunderstorms, tornadoesSevere-hurricanes, thunderstorms, tornadoes

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ClimateClimate ClimateClimate – long term weather patterns – long term weather patterns

– driven by atmospheredriven by atmosphere– Uneven heating of earth’s surfaceUneven heating of earth’s surface

EquatorEquator Seasonal changes in temp and precipSeasonal changes in temp and precip Opposite seasons in N&S hemispheresOpposite seasons in N&S hemispheres

– determines distribution of biomes across Earthdetermines distribution of biomes across Earth

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What Factors Control Climate?What Factors Control Climate?

LatitudeLatitude Elevation/topographyElevation/topography Nearby waterNearby water Ocean currentsOcean currents VegetationVegetation Prevailing windsPrevailing winds

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Ocean CurrentsOcean Currents Warm/cold currents influence land climateWarm/cold currents influence land climate Currents redistribute heat from sun which influences climateCurrents redistribute heat from sun which influences climate

– El NinoEl Nino – change in the direction of tropical winds warms SA – change in the direction of tropical winds warms SA and NA coastal surface waters, suppresses upwellings, and and NA coastal surface waters, suppresses upwellings, and alters weatheralters weather Warm water spreads from the west Pacific to the east Warm water spreads from the west Pacific to the east

PacificPacific EffectsEffects

– Distorts jet streamDistorts jet stream– Reduces primary productivityReduces primary productivity

Some fish species declineSome fish species decline– La NinaLa Nina -cooling counterpart -cooling counterpart

Upwelling of nutrient rich waterUpwelling of nutrient rich water

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““Natural” Greenhouse EffectNatural” Greenhouse Effect Solar radiation passes through the atmosphere. Solar radiation passes through the atmosphere.

– ~51% of the sun's radiation reaches the surface~51% of the sun's radiation reaches the surface This energy is then used in number of processes including: This energy is then used in number of processes including:

– heating of the ground surfaceheating of the ground surface

– melting of ice and snowmelting of ice and snow

– evaporation of waterevaporation of water

– plant photosynthesisplant photosynthesis

– ~30% is reflected back to space by clouds and the surface~30% is reflected back to space by clouds and the surface

– ~19% of the energy available is absorbed by clouds and gases ~19% of the energy available is absorbed by clouds and gases Gases absorb and reradiate this outgoing radiation, effectively storing Gases absorb and reradiate this outgoing radiation, effectively storing

some of the heat in the atmosphere, thus producing a net warming of some of the heat in the atmosphere, thus producing a net warming of the surfacethe surface

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““Natural” Greenhouse Effect cont.Natural” Greenhouse Effect cont.

This process has kept the Earth's temperature This process has kept the Earth's temperature about 60 degrees Fahrenheit warmer than it about 60 degrees Fahrenheit warmer than it would otherwise be. would otherwise be.

Life on Earth could not be sustained without the Life on Earth could not be sustained without the natural greenhouse effect.natural greenhouse effect.