lecture15 - geowiki.ucsd.edu · 3) earth’s tilted axis orbits sun! sun in zenith at different...

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SIO15-19: Lecture15: The Atmosphere and Climate


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climate: average long-term condition; controlled by location regional to globalweather: short-term condition; controlled by atmospheric anomalies local to regional

climate: “I live in San Diego because it rains in Seattle”

weather: “San Diego got soaked last week”


how much solar radiation is received in any area?

insolation per area:greater when Sun is overhead than near poles

Marshak: Earth, Portrait of a Planet

zenith

seasonswatchshortVideo15a

annually 2.4 times lowerat poles than at equator

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how much solar radiation is retained in any area?

Albedo: fraction of insolation reflected back to space

- 80% fresh snow- 25% grass- 10% oceans

THE DUAL FUNCTION OF H2O

WATER VAPOR: most abundant greenhouse gas (warms)

CLOUDS: reflect sunlight back into space (cools)




- 30% reflected back to space- 51% absorbed at surface-  19% absorbed by atmosphere

Earth’s surface emits more heat (IR) than it receives

Ahrens: Meteorology Today

see Fig 11.4

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+ 1% other stuff- 0.93% Ar- CO2 400ppm (0.04%)- Ne 18ppm- He 5ppm- CH4 2ppm- Kr 1ppm

mainly N2 and O2+ 0-4% water vapor (H2O) (variable)

Greenhouse Gases: H2O, CO2, CH4

watchshortVideo15b


Which element is the main contributor to Earth’s atmosphere?

(0.33 pt)

Write your own pop quiz only. Have your student ID ready.Submitting a pop quiz for your friend is cheating!

We check handwriting.Suspected cheaters will lose ALL previous PQ credits!Students in class less than 20 min are NOT eligible to get PQ credit.

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Earth’s atmosphere acts like a greenhouse

greenhouse gases: H2O, CO2, CH4-  transparent to visible, UV light-  absorb infrared-  reflect IR back to Earth- > trap heat

Earth with greenhouse:16ºC/61ºFEarth without greenhouse: 34ºC/61ºF colder -> -18ºC/0ºF

Fig 11.8

H2O most abundant greenhouse gas


What is Earth’s most abundant greenhouse gas?(0.34 pt)



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3) Earth’s tilted axis orbits Sun!  sun in zenith at different times (+/- 23.5º N/S)!  local insolation changes throughout the year


Fig 11.15

summer in San Diegobut winter in Santiago, Chile


SIO15-19: Lecture15: The Atmosphere and ClimateMarshak: Earth, Portrait of a Planet

oppositeseasonsbetweenNandShemispheres

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Abbott: Natural Disasters



polar ice, subpolar Tundra, subtropical (temperate), dry land (desert), tropicalplus: highland, continental


see Fig 11.7

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Which season is it in Santiago, Chilewhen it is winter in San Diego? (0.33 pt)




•  oceans store more heat than atmosphere •  oceans are climate moderators (negative feedback) !  coastal areas have less extreme climate

Heat Capacity: ability to absorb heat without getting hot

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- ocean processes longer-term than atmospheric processes- > ocean currents slower than atmospheric winds-  currents blocked by continents-  Driving Mechanism: cold and salty water sinks (thermohaline circulation)

source: Wikipedia

exact shape of heat conveyor not well known


Ocean Surface Currents


-  warm western boundary currents (e.g. Gulf Stream)-  cold eastern boundary currents (e.g. California Current) (think May Grey/June Gloom!)

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!  atmosphere has less CO2 than humans produced in last 150 yrs!  oceans take up CO2!  it’s not (only) the rain forest!!  leads to ocean acidification

but what we do know!


50% air below 5.6 km 90% air below 16 km 99.99997% below 100km

•  air pressure: push due to weight of atmosphere above•  greatest at sea level: 1 atmosphere, 14.7 PSI, 1035 mbar (g/cm2)•  pressure and density decrease exponentially with altitude

simple

watchshortVideo15b

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troposphere: lower 10km; weather layer, mixingstratosphere: next 35km; very dry, no vertical mixing, O3 layermesosphere: less O3; meteorites burn upthermosphere: < 1% air; (ISS at ~350 km)

Layers follow T-function


it takes 600 cal to evaporate 1g waterevaporation: water vapor absorbs heat

condensation: water vapor releases heat

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SIO15-19: Lecture15: The Atmosphere and Climateverysimilartopast2weeks

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lecture15 - geowiki.ucsd.edu · 3) earth’s tilted axis orbits sun! sun in zenith at different...

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