The AtmosphereThe Atmosphere

Structure and ChangeStructure and Change

OverviewOverview

StructureStructure Compositional structureCompositional structure Temperature structureTemperature structure Functional structureFunctional structure

ChangeChange Natural sources of changeNatural sources of change Natural influences on Natural influences on

pollutionpollution Anthropogenic pollutionAnthropogenic pollution

GeneralGeneral Thermopause is considered the outermost boundary Thermopause is considered the outermost boundary

of the atmosphere.of the atmosphere. 480km, 300 mi above surface480km, 300 mi above surface

The Exosphere extends beyond the thermopauseThe Exosphere extends beyond the thermopause Rarefied (near vacuum)Rarefied (near vacuum) Sparse Hydrogen and Helium atomsSparse Hydrogen and Helium atoms Extends to 20,000 miles (32,000 km) from Earth’s surfaceExtends to 20,000 miles (32,000 km) from Earth’s surface

Density of Atmosphere increases near the surfaceDensity of Atmosphere increases near the surface 90% of atmospheric mass occurs within 16,000 meters of 90% of atmospheric mass occurs within 16,000 meters of

surfacesurface Air pressure (sea level): 1013.2 mb; 101.32 kPa; 29.92 inAir pressure (sea level): 1013.2 mb; 101.32 kPa; 29.92 in

Air pressure decreases with decreasing density (i.e., altitude)Air pressure decreases with decreasing density (i.e., altitude)

Atmospheric gases held by Earth’s Atmospheric gases held by Earth’s gravitygravity Earth’s gravity weakens with altitudeEarth’s gravity weakens with altitude Changes density profileChanges density profile Sorts atmosphere into different layersSorts atmosphere into different layers

Three different ways of looking at Three different ways of looking at atmospheric layeringatmospheric layering CompositionComposition

HomosphereHomosphere HeterosphereHeterosphere

TemperatureTemperature Troposphere (Tropopause)Troposphere (Tropopause) Stratosphere (Stratopause)Stratosphere (Stratopause) Mesosphere (Mesopause)Mesosphere (Mesopause) Thermosphere (Thermopause)Thermosphere (Thermopause)

FunctionFunction OzonosphereOzonosphere IonosphereIonosphere

CompositionComposition HomosphereHomosphere

Gases evenly Gases evenly mixedmixed

ExceptionsExceptions Water vapor Water vapor

(clouds)(clouds) Ozone layer Ozone layer Point sources at Point sources at

surfacessurfaces Over 99% of Over 99% of

AtmosphereAtmosphere HeterosphereHeterosphere

Uneven mixture Uneven mixture of gases, sorted of gases, sorted by atomic and by atomic and molecular weightmolecular weight

TemperatureTemperature TroposphereTroposphere 90% of Atmosphere90% of Atmosphere

Nearly all of the water vapor and weatherNearly all of the water vapor and weather Supports lifeSupports life Upper boundary: TropopauseUpper boundary: Tropopause

18 km (11mi) at equator, 12 km (8 mi) mid-18 km (11mi) at equator, 12 km (8 mi) mid-latitudes, 8 km (5 mi) at poleslatitudes, 8 km (5 mi) at poles

Varies with temperature (solar heating)Varies with temperature (solar heating) Temperatures decrease with altitudeTemperatures decrease with altitude

Normal Lapse Rate: 6.4Normal Lapse Rate: 6.4ooC/km (3.5C/km (3.5ooF/ft)F/ft) Environmental Lapse RateEnvironmental Lapse Rate InversionsInversions Crucial for understanding weatherCrucial for understanding weather Heated by the Earth’s surfaceHeated by the Earth’s surface

StratosphereStratosphere MesosphereMesosphere ThermosphereThermosphere

StratosphereStratosphere 18 – 50 km (11 –31 mi) above surface18 – 50 km (11 –31 mi) above surface Ozone layerOzone layer Temperature increases with altitudeTemperature increases with altitude

Heating from absorption of ultraviolet light by Heating from absorption of ultraviolet light by ozoneozone

At lower levels, heated by surface emanations as At lower levels, heated by surface emanations as wellwell

Upper boundary: StratopauseUpper boundary: Stratopause MesosphereMesosphere

50 – 80km (30 – 50 mi) above surface50 – 80km (30 – 50 mi) above surface Temperature decreases with altitudeTemperature decreases with altitude Upper boundary: MesopauseUpper boundary: Mesopause

Coldest region in atmosphereColdest region in atmosphere Emanations from the stratosphere provide heat Emanations from the stratosphere provide heat

sourcesource

ThermosphereThermosphere 80 – 480 km (50-300 mi) on average80 – 480 km (50-300 mi) on average Upper Boundary: ThermopauseUpper Boundary: Thermopause

Actual altitude varies between 250 – 550 km Actual altitude varies between 250 – 550 km (155 – 340 mi)(155 – 340 mi)

Increases with increased solar activityIncreases with increased solar activity

Extremely high temperatures but little Extremely high temperatures but little sensible heatsensible heat

Heated by direct exposure to incoming solar Heated by direct exposure to incoming solar radiationradiation

Air particles have extremely high kinetic energy Air particles have extremely high kinetic energy (temperature)(temperature)

Low density of particles means fewer collisions Low density of particles means fewer collisions of particles, lower overall capacity to store heatof particles, lower overall capacity to store heat

FunctionFunction Classifies atmospheric layers Classifies atmospheric layers

according to how they shield the according to how they shield the surface from harmful radiationsurface from harmful radiation

OzonosphereOzonosphere OO33

Absorbs short-wave radiation and Absorbs short-wave radiation and reradiates it as long-wave radiationreradiates it as long-wave radiation

Shields surface from harmful Shields surface from harmful ultraviolet radiationultraviolet radiation

Various pollutants deplete ozoneVarious pollutants deplete ozone IonosphereIonosphere

OzonosphereOzonosphere IonosphereIonosphere

Absorbs short-Absorbs short-wave radiationwave radiation

Cosmic rays, Cosmic rays, Gamma rays, X-Gamma rays, X-rays, shorter UVrays, shorter UV

High energy High energy radiation tends radiation tends to knock to knock electrons off of electrons off of the atmospheric the atmospheric gas atoms, gas atoms, producing producing positively positively charged ionscharged ions