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