Characteristics of the atmosphereCharacteristics of the atmospherelecture 22.1blecture 22.1b

CompositionComposition

Gases in air:Gases in air:N 78%N 78%

OO22 21% 21%

Argon 0.93%Argon 0.93%

COCO22 .035% .035%

• Thickness: Thickness: 400 mi. from 400 mi. from surface to surface to space.space.

TroposphereTroposphere

Layer closest to Layer closest to ground.ground.

OO22 and H and H22O are O are most dense.most dense.

All weather occurs All weather occurs in this layer.in this layer.

With elevation, With elevation, temperature and temperature and OO22 decrease. decrease.

Temperature Temperature InversionsInversions

Happen when Happen when warm air sits warm air sits above above cold air. cold air.

Pollutants are Pollutants are trapped near the trapped near the ground.ground.

Ex: ‘spare the air’ Ex: ‘spare the air’ days/nights, smogdays/nights, smog

StratosphereStratosphere

Ozone layer in Ozone layer in upper region.upper region.

OO33 molecules molecules absorbabsorb UV UV radiation from radiation from sun, sun, pprotectingrotecting life.life.

Ozone “hole”Ozone “hole” Use of CFCs has Use of CFCs has

caused a caused a thinningthinning of the of the ozone layer.ozone layer.

CFCs are in CFCs are in refrigerants, refrigerants, A/C and A/C and aerosolsaerosols

Result: more Result: more UV radiationUV radiation hit hit earth.earth.

RecoveryRecovery Nations Nations

agreed to agreed to stopstop using CFCs in using CFCs in 1987.1987.

The ozone The ozone layer appears layer appears to be getting to be getting thicker again.thicker again.

UUpper atmospherepper atmosphere IonosphereIonosphere: Radio : Radio

waves reflect off waves reflect off ionsions in this layer (farther @ in this layer (farther @ night)night)

ThermosphereThermosphere: 980 C : 980 C Satellites, Satellites,

International Space International Space StationStation

Sunrise from the Space Shuttle

Magnetosphere and plasmasphereprotect earth from solar wind, radiation.Generated by earth’s magnetic field.

Aurora borealisAurora borealis

AurorasAuroras circle the earth’s magnetic poles. circle the earth’s magnetic poles. Solar energy excites ions- Solar energy excites ions- photons of light photons of light

are released are released as e- fall back to lower E as e- fall back to lower E levels.levels.

Changes over timeChanges over time

Early earth’s atmosphere was toxic.Early earth’s atmosphere was toxic. Volcanoes Volcanoes out-gassed methane (CHout-gassed methane (CH44) CO) CO2, 2,

HH22O.O. CometsComets added organic molecules. added organic molecules.

PhotosynthesisPhotosynthesis

Later, Later, algae+ plantsalgae+ plants develop ability to develop ability to use sunlight to store energy.use sunlight to store energy.

Oxygen in atmosphere was created by this Oxygen in atmosphere was created by this processprocess: 20% of air today.: 20% of air today.

CO2 + H2O C6H12O6 + O2

Carbon/Carbon/Oxygen Oxygen

cyclecycle

Plants and the oceans Plants and the oceans absorbabsorb Carbon. Carbon. Respiration and burningRespiration and burning releaserelease Carbon as CO Carbon as CO2 .2 .

Greenhouse effectGreenhouse effect

Greenhouses are warmer than their Greenhouses are warmer than their surroundings.surroundings.

Their walls Their walls prevent heat from escapingprevent heat from escaping, , trapping it inside.trapping it inside.

Greenhouse gasesGreenhouse gases

COCO2, 2, HH22OO gas in the atmosphere warms the earth. gas in the atmosphere warms the earth. Burning fossil fuelsBurning fossil fuels has has greatly increasedgreatly increased CO CO22

levels.levels. Effect: our planet is Effect: our planet is warmingwarming at a rapid rate. at a rapid rate.