What is air?What is the atmosphere?Atmosphere—static or dynamic?How formed?H, He diffusedVolcanic emissions: C, N, O, SPhotosynthesisAtmosphereCloak of air held in place by gravityComponents—Nitrogen:78%Oxygen: 21%Argon: 0.9%Carbon Dioxide: 0.035%Neon: 0.00182%Atmosphere“Ocean” of gas and aerosolsAerosols: minute particles & liquid droplets500 km or 300 miles thickAtmosphereZones of different temperaturesTroposphereStratosphereMesosphereThermosphereComposition & behavior—control weather and climateZonesTroposphere—next to surfaceMost directly affects living systemsThin, 11km (7 mi)75% of atmosphere’s massTemperature drops 6° C/kmTropopauseLowest temperature: -62°CTropopause—temperature no longer decreases with altitude, reversalActs as cap, prevents mixingTroposphereConstantly movingCirculation in horizontal and vertical convection currentsHeat and moisture redistributed globallyStratosphere11km->50 kmSimilar in composition, little H2O vapor, 1000 x more ozoneTemperature rises with altitudeOzone absorbs UV-B (290-330 nm)Makes surface warmerStratosphereAbsorption by ozone decreases UV-caused cellular damageLittle mixingContaminants (natural & man-made) remain suspendedStratopause—temperature drop with altitudeMesosphere50 km -> 90 kmLow air pressureTemperatures fall with altitude-90°Thermosphere90 km -> 500 kmTemperature rises to 1700°CIonized gases react with solar and cosmic radiation: aurorasSame composition, very low concentrationN & O sink, H & He riseDiffuses into spaceEnergy (again)1000 watts/m2 from sun70% absorbed by atmosphere and surface30% reflectedAlbedo—reflectivitySnow, clouds, water (low sun)EnergySecond Law of ThermodynamicsComes in as lightRe-emitted as heat, far infraredAtmospheric gases (CO2 and H2O) absorb ERelease to lower atmosphereHeat leaks slowlyGreenhouse EffectAtmosphere transmits lightTraps heatMaintains warmthNatural processHuman activities enhanceGreenhouse gases: CO2, H2O, O3, N2O, CFCs, HFCs, CH4Air, Weather, ClimateWhat is air?What is air?What is the atmosphere?What is the atmosphere?AtmosphereAtmosphere——static or dynamic?static or dynamic?How formed?How formed?H, He diffusedH, He diffusedVolcanic emissions: C, N, O, SVolcanic emissions: C, N, O, SPhotosynthesisPhotosynthesisAtmosphereAtmosphereCloak of air held in place by gravityCloak of air held in place by gravityComponentsComponents——Nitrogen:78%Nitrogen:78%Oxygen: 21%Oxygen: 21%Argon: 0.9%Argon: 0.9%Carbon Dioxide: 0.035%Carbon Dioxide: 0.035%Neon: 0.00182%Neon: 0.00182%Atmosphere Atmosphere ““OceanOcean”” of gas and aerosols of gas and aerosolsAerosols: minute particles & liquid dropletsAerosols: minute particles & liquid droplets500 km or 300 miles thick500 km or 300 miles thickAtmosphereAtmosphereZones of different temperaturesZones of different temperaturesTroposphereTroposphereStratosphereStratosphereMesosphereMesosphereThermosphereThermosphereComposition & behaviorComposition & behavior——control weather and control weather and climate climateZonesZonesTroposphereTroposphere——next to surfacenext to surfaceMost directly affects living systemsMost directly affects living systemsThin, 11km (7 mi)Thin, 11km (7 mi)75% of atmosphere75% of atmosphere’’s masss massTemperature drops 6° C/kmTemperature drops 6° C/kmTropopause Tropopause Lowest temperature: -62°CLowest temperature: -62°CTropopauseTropopause——temperature no longer decreases with temperature no longer decreases with altitude, reversalaltitude, reversalActs as cap, prevents mixing Acts as cap, prevents mixing TroposphereTroposphereConstantly movingConstantly movingCirculation in horizontal and vertical convection Circulation in horizontal and vertical convection currentscurrentsHeat and moisture redistributed globallyHeat and moisture redistributed globallyStratosphereStratosphere11km->50 km11km->50 kmSimilar in composition, little HSimilar in composition, little H22O vapor, 1000 x O vapor, 1000 x more ozonemore ozoneTemperature rises with altitudeTemperature rises with altitudeOzone absorbs UV-B (290-330 nm)Ozone absorbs UV-B (290-330 nm)Makes surface warmerMakes surface warmerStratosphere Stratosphere Absorption by ozone decreases UV-caused Absorption by ozone decreases UV-caused cellular damagecellular damageLittle mixingLittle mixingContaminants (natural & man-made) remain Contaminants (natural & man-made) remain suspendedsuspendedStratopauseStratopause——temperature drop with altitudetemperature drop with altitudeMesosphere Mesosphere 50 km -> 90 km50 km -> 90 kmLow air pressureLow air pressureTemperatures fall with altitudeTemperatures fall with altitude-90°-90°Thermosphere Thermosphere 90 km -> 500 km90 km -> 500 kmTemperature rises to 1700°CTemperature rises to 1700°CIonized gases react with solar and cosmic Ionized gases react with solar and cosmic radiation: aurorasradiation: aurorasSame composition, very low concentrationSame composition, very low concentrationN & O sink, H & He riseN & O sink, H & He riseDiffuses into spaceDiffuses into spaceEnergy (again)Energy (again)1000 watts/m1000 watts/m2 2 from sunfrom sun70% absorbed by atmosphere and surface70% absorbed by atmosphere and surface30% reflected30% reflectedAlbedoAlbedo——reflectivityreflectivitySnow, clouds, water (low sun)Snow, clouds, water (low sun)EnergyEnergySecond Law of ThermodynamicsSecond Law of ThermodynamicsComes in as lightComes in as lightRe-emitted as heat, far infraredRe-emitted as heat, far infraredAtmospheric gases (COAtmospheric gases (CO22 and H and H22O) absorb E O) absorb E Release to lower atmosphereRelease to lower atmosphereHeat leaks slowly Heat leaks slowlyGreenhouse EffectGreenhouse EffectAtmosphere transmits lightAtmosphere transmits lightTraps heatTraps heatMaintains warmthMaintains warmthNatural processNatural processHuman activities enhanceHuman activities enhanceGreenhouse gases: COGreenhouse gases: CO22, H, H22O, OO, O33, N, N22O, CFCs, O, CFCs, HFCs, CHHFCs,