The AtmosphereThe Atmosphere

What is weather?What is weather?

• state of the atmosphere state of the atmosphere at a given time and placeat a given time and place

Who studies the weather?Who studies the weather?

MeteorologistsMeteorologists – scientists – scientists

MeteorologyMeteorology – study of the atmosphere – study of the atmosphere and related phenomenaand related phenomena

WGN ChicagoWGN ChicagoTom SkillingTom Skilling

NBC ChicagoNBC ChicagoGinger ZeeGinger Zee

Look at the following pictures. Think Look at the following pictures. Think about how these pictures relate to about how these pictures relate to

Earth’s dynamic atmosphere.Earth’s dynamic atmosphere.

How did Earth’s atmosphere form?How did Earth’s atmosphere form?

VolcanoesVolcanoes(Nitrogen, Sulfur, CO, CO(Nitrogen, Sulfur, CO, CO22, CH, CH44))

CometsComets(H(H22O)O)

PhotosynthesisPhotosynthesis(O(O22))

Composition of the AtmosphereComposition of the Atmosphere

Lower atmosphereLower atmosphere•99% of atmosphere in the 99% of atmosphere in the

lowermost 32 kmlowermost 32 km

Upper atmosphereUpper atmosphere•~~vacuum (low air pressure)vacuum (low air pressure)•composition changescomposition changes

•oxygen layer oxygen layer helium layer helium layer hydrogen layer hydrogen layer outer space outer space

Earth’s layered atmosphereEarth’s layered atmosphere•based on temperature and composition differencesbased on temperature and composition differences

ozone absorbs energy in stratosphere

~ 70% atmosphere in troposphere

Temperature changes with altitudeTemperature changes with altitude

Our atmosphere is Our atmosphere is very thinvery thin compared to the size of Earth.compared to the size of Earth.

Troposphere composition Troposphere composition

ppmv: parts per million by volume

Gas Volume

Nitrogen (N2) 78.084%

Oxygen (O2) 20.946%

Argon (Ar) 0.9340%

Carbon dioxide (CO2) 365 ppmv

Neon (Ne) 18.18 ppmv

Helium (He) 5.24 ppmv

Methane (CH4) 1.745 ppmv

Krypton (Kr) 1.14 ppmv

Hydrogen (H2) 0.55 ppmv

Not included in above dry atmosphere:

Water vapor (highly variable) typically 1%

The ionosphereThe ionosphere• layers in mesosphere & layers in mesosphere &

thermosphere containing thermosphere containing ionsions

• affects travel of affects travel of radio wavesradio waves–radio travels farther at nightradio travels farther at night

• aurorasauroras = solar particles = solar particles interacting with the ionosphereinteracting with the ionosphere

ionosphereionosphere•affects radio wavesaffects radio waves•influences aurorasinfluences auroras

AurorasAurorasions interacting with ions interacting with atmospheric gases atmospheric gases and solar particlesand solar particles

radio wavesradio wavestravel farther travel farther

at nightat night

Earth’s Heat BudgetEarth’s Heat Budget• insolationinsolation ( (inincoming coming solsolar radiar radiationation))

• most of atmosphere’s energy transferred most of atmosphere’s energy transferred from the surfacefrom the surface– radiation (infrared)radiation (infrared)

• absorbed by carbon dioxide and water vapor absorbed by carbon dioxide and water vapor (greenhouse effect)(greenhouse effect)

– conduction and convectionconduction and convection– evaporation of waterevaporation of water

Earth’s heat budgetEarth’s heat budget

Human activity can affect Earth’s heat budget.Human activity can affect Earth’s heat budget.

Chemical and transport processes Chemical and transport processes related to atmospheric composition related to atmospheric composition

Causes of Local temperature Causes of Local temperature variationsvariations

• Intensity of insolationIntensity of insolation– incoming solar radiation from the Sunincoming solar radiation from the Sun

• Time of DayTime of Day– morning vs. noonmorning vs. noon

• LatitudeLatitude– Equator vs. PolesEquator vs. Poles

• Time of YearTime of Year– winter vs. summerwinter vs. summer

• Cloud CoverCloud Cover– clouds trap heatclouds trap heat

• Differential heatingDifferential heating– land vs. water vs. snowland vs. water vs. snow

Intensity of Insolation varies with:

1.Time of Day• More direct/vertical radiation (closer to 90 ˚) = more intense

• At noon, the sun’s rays are closest to 90 ˚

• However, warmest time of day is usually around 3:00 PM

• Coolest time of day usually right before sunrise

2.Latitude• Angle of sunlight varies with latitude

• Equator receives almost vertical rays year round – HOT

• Poles receive sun’s rays at low angles - COLD

3.Time of Year• More direct rays – warmer; usually warmer a month after maximum

insolation

• Example: Here it is warmest in July & maximum insolation is in June (summer solstice)

• Least direct rays – cooler a month after; January is our coolest month; December is time of minimum insolation

4. Cloud cover• Clouds reflect sunlight; warmer on a clear day

• Clouds hold in heat; warmer on a cloudy night

Surfaces heat up more if the Surfaces heat up more if the Sun is more directly overheadSun is more directly overhead

SummerSummer WinterWinter

Sun rays strike Earth from 0Sun rays strike Earth from 0° to 90°° to 90°

More atmosphere to go through reflects more lightMore atmosphere to go through reflects more light

Insolation varies with latitude and time of yearInsolation varies with latitude and time of year

Temperatures of land vary more than Temperatures of land vary more than water due to land’s low specific heatwater due to land’s low specific heat

Temperature Maps

Isotherms

•

Isotherms

• Lines drawn onweather map toshow places withthe sametemperature

• One isotherm linerepresents 5 - 10 ˚

• Lines are notstraight becauseland and water heatand cool differently

• Are more regular in the Southern Hemisphere because mostly water

• Bend toward poles in a warmer area

• Bend toward equator in a colder area

• In Northern Hemisphere shift: *Northward in July

*Southward in January

Isotherms = equal temperature linesIsotherms = equal temperature lines

Complex patterns based on land cover and elevationComplex patterns based on land cover and elevation

Human Impacts on the AtmosphereHuman Impacts on the Atmosphere

• ParticulatesParticulates– smoke, dust, and ashsmoke, dust, and ash

• Acid rainAcid rain– sulfur and nitrogen emissionssulfur and nitrogen emissions

• SmogSmog– automobile exhaustautomobile exhaust

• Ozone depletionOzone depletion– CFC emissionsCFC emissions

• Global warmingGlobal warming– greenhouse gases like COgreenhouse gases like CO22 and CH and CH44

Temperature Temperature InversionsInversions

• The troposphere The troposphere usuallyusually cools with cools with increasing altitudeincreasing altitude

• InversionInversion = layer of = layer of air near the ground air near the ground where temperature where temperature increases with increases with increasing altitudeincreasing altitude– usually forms early in usually forms early in

the morning after a the morning after a clear night.clear night.

Los Angeles, CALos Angeles, CA•temperature inversions temperature inversions

keep smog near the groundkeep smog near the ground

The Ozone “Hole” is carefully The Ozone “Hole” is carefully monitored by scientistsmonitored by scientists

It is not really a hole…just a region It is not really a hole…just a region of lower ozone concentration of lower ozone concentration

•Ozone blocks UV lightOzone blocks UV light•CFCs destroy ozoneCFCs destroy ozone•CFCs remain in the CFCs remain in the atmosphere for yearsatmosphere for years

The ozone hole is the region over Antarctica with total ozone of 220 Dobson Units or lower. This map shows the ozone hole on October 4, 2004. The data were acquired by

the Ozone Monitoring Instrument on NASA’s Aura satellite.

Largest Recorded Ozone HoleLargest Recorded Ozone HoleSeptember 2006September 200626 million km26 million km22

What if the world never What if the world never stopped using CFCs?stopped using CFCs?

•simluation showing the size of the simluation showing the size of the ozone hole by 2054ozone hole by 2054

•global ozone drops by halfglobal ozone drops by half•short wavelenght skin cancer-short wavelenght skin cancer-causing radiation hundreds to causing radiation hundreds to thousands of time as intensethousands of time as intense

Internet Link

Red = high concentrationsBlue = low concentrations

Greenhouse EffectGreenhouse Effect•certain gases absorb outgoing infrared certain gases absorb outgoing infrared

radiation and heat the atmosphereradiation and heat the atmosphere

Without the Without the Greenhouse EffectGreenhouse Effect Earth would be Earth would be ~ 60° F cooler~ 60° F cooler

Greenhouses (analogy)Greenhouses (analogy)•heats up because the Sun warms the ground inside itheats up because the Sun warms the ground inside it

•ground warms the air near the groundground warms the air near the ground•air is prevented from rising and flowing away.air is prevented from rising and flowing away.

•warming thus occurs by suppressing convectionwarming thus occurs by suppressing convection

CoolerCooler

HotterHotter

Greenhouse GasesGreenhouse Gases• Naturally occurring:Naturally occurring:

– water vaporwater vapor– carbon dioxidecarbon dioxide– ozoneozone– methanemethane– nitrous oxidenitrous oxide

• Human emissions:Human emissions:– carbon dioxidecarbon dioxide– methane (livestock)methane (livestock)– CFCs (chlorofluorocarbons)CFCs (chlorofluorocarbons)– HCFCsHCFCs (hydrochlorofluorocarbons)– HFCs (hydrofluorocarbons)

Yearly fluctuation due to seasonal plant growth (Northern Hemisphere)

Long-term increases in COLong-term increases in CO22 most most

likely caused by likely caused by human emissionshuman emissions

Humans are rapidly adding to the Humans are rapidly adding to the level of greenhouse gases!level of greenhouse gases!

power-plants

livestock

deforestation transportation

Consumer decisions that you make can help to Consumer decisions that you make can help to reduce greenhouse gas emissions.reduce greenhouse gas emissions.

Website – Carbon offsetWebsite – Carbon offset

Hybrid vehicleHybrid vehiclefuel economy gauges help you fuel economy gauges help you

drive more efficientlydrive more efficiently

Consumer can also offset fossil fuel electricity use with renewable Consumer can also offset fossil fuel electricity use with renewable energy certicicatesenergy certicicates

The future?The future?Can humans use natural resources in a Can humans use natural resources in a

sustainable manner, minimize the sustainable manner, minimize the warming of the atmosphere, and prevent warming of the atmosphere, and prevent

likely outcomes of global warming?likely outcomes of global warming?Tropical diseases Tropical diseases

increaseincrease

Sea levels rise as glaciers meltSea levels rise as glaciers melt Species endangered Species endangered or extinctor extinct