1. The Atmosphere (Abridged)
Purpose: The purpose of this presentation is to provide APES students with important information on the atmosphere.
Objective: At the end of this presentation students will have generated notes necessary to understand key processes in the Earth’s atmosphere.

2. The Atmosphere-history
3.2 billion years ago (bya) atmosphere mostly steam and CO2 (Life begins in sea)
bya photosynthetic bacteria (cyanobacteria) began producing oxygen
mya ozone levels in stratosphere sufficient to protect land plants from UV radiation.

3. The Atmosphere-current composition
Around 1% Ar2
0.01-4% H2O
0.037 CO2

4. The Atmosphere-current composition
The Greenhouse Effect
- Natural warming effect of the troposphere
1. sunlight hits the Earth’s surface turning into infrared (heat) radiation
2. heat risessome escapes into space
some heats greenhouse gases emitting infrared radiation which warm the troposphere +

5. The Atmosphere-current composition
Major greenhouse gases:
water vapor (primary)
CO2
O3 (ozone)
CH4 (methane)
N2O (nitrous oxide)
CFCs (chlorofluorocarbons)

6. The Atmosphere-current composition
Mean global temperature
14.53oC or 58.14oF ( )
14.0oC or 57.2oF ( )
(Source
-18oC or 0oF without greenhouse effect

7. The Atmosphere-Climate
Climate: Regional patterns of atmospheric conditions
-mainly influenced by average temperature and precipitation
-globally follows a cyclic pattern
+ glacial periods lasting around 100,000 yrs
+ interglacial periods lasting around 10,000 yrs
+ Holocene epoch—nearing end of interglacial period

8. The Atmosphere-climate
Factors that affect global climate
shape of the Earth’s orbit (eccentricity)
“wobble” of the Earth’s axis (precession)
changes in the tilt of the Earth’s axis (obliquity)
volcanic activity
changes in solar output
atmospheric composition

9. The Atmosphere-climate
Factors that affect regional climate
uneven heating of the Earth’s surface (varies by latitude and season)
rotation of the Earth
ocean currents
mountains
altitude
tilt of the Earth

10. The Atmosphere-factors that affect regional climate
Uneven heating of the Earth’s surface
Consistent, year-round heating at equator
More seasonal variation as latitude increases
Uneven heating produces atmospheric areas of low pressure (less dense, rising air) and high pressure (more dense, falling air.)
Pattern alternates about every 30 degree change in latitude (p. 125)

11. The Atmosphere-factors that affect regional climate: Earth’s rotation
Coriolis Effect—The apparent deflection of a moving object due to the motion of the Earth underneath it

12. The Atmosphere-factors that affect regional climate: ocean currents
Water’s high specific heat causes it to gain and lose heat slower than land masses
Oceans produce milder climates
Changes in density due to temperature differences and the Earth’s rotation produce ocean circulation patterns
Europe is warmer than it should be due to warm ocean currents

13. The Atmosphere-factors that affect regional climate: ocean currents

14. The Atmosphere-factors that affect regional climate: mountains
Mountains force air masses to rise as they pass across them
Rising air cools and moisture condenses producing precipitation on the “windward’ side
Descending air on the “leeward” side has less moisture producing areas of lower precipitation
Rain shadow effect

15. The Atmosphere-factors that affect regional climate: mountains

16. The Atmosphere-factors that affect regional climate: altitude
Average temperature decreases about 3oF for every 1000 feet in altitude Barrons p. 117

17. The Atmosphere-factors that affect regional climate: tilt of the Earth
The Seasons!

18. The Atmosphere-weather
Weather-The short-term conditions in the troposphere at a location.
Includes atmospheric conditions such as
- temperature
- pressure
- relative humidity
- sunshine
- cloud cover
- wind direction and speed

19. The Atmosphere-weather: temperature
Measure of kinetic energy
Differences produced by uneven heating of Earth’s surface
Maps of areas with the same temperatures are called isotherms

20. The Atmosphere-weather: temperature

21. The Atmosphere-weather: temperature
Normally troposphere gets cooler with altitude
Temperature inversion--a layer or warmer air above cooler surface air
- subsidence inversionlarge mass of warmer air moves into a region, floats over top of stationary cooler air
- radiation inversionat night air near the ground cools faster than air above

22. The Atmosphere-weather: temperature

23. The Atmosphere-weather: temperature
Cold Front—leading edge of advancing mass of cold air
-more dense so slides under warmer air lifting it
-rising warm air produces thunderheads and rainstorms

24. The Atmosphere-weather: temperature-Cold Front

25. The Atmosphere-weather: temperature
Warm Front—leading edge of advancing mass of warm air
-less dense so rises up over colder air
-more gradual lifting produces thickening clouds and longer periods of rain

26. The Atmosphere-weather: temperature-Warm Front

27. The Atmosphere-weather: temperature (note symbols)

28. The Atmosphere-weather: clouds
Condensation of water vapor in rising air due to lower temperatures.
Atmospheric conditions determine cloud type
Cloud names indicate appearance and altitude

29. The Atmosphere-weather: Clouds
Cirrus Clouds:
-High altitude
-Thin and wispy

30. The Atmosphere-weather: Clouds
Stratus Clouds
-lower altitude
-layered and sheetlike

31. The Atmosphere-weather: Clouds
Cumulus Clouds
-Low to medium altitude
-Flat bottom and fair weather
-Cumulonimbus are thunderstorm clouds

32. The Atmosphere-weather: Pressure
Earth’s gravity pulling down on molecules in the atmosphere creates atmospheric pressure
Atmospheric pressure at sea level is:
- 760 mm of Hg
in. of Hg
psi
millibar

33. The Atmosphere-weather: Pressure
Maps of areas with the same barometric pressure are called isobars
Areas of low pressure bring cloudy rainy weather. Counterclockwise (NH) (cyclone)
Areas of high pressure usually indicate clear weather. Clockwise (NH) (anticyclone)
Air moves from areas of high pressure into areas of low pressure—wind!

34. The Atmosphere-weather: Pressure

35. The Atmosphere-weather: Pressure

36. The Atmosphere-weather: Jet Stream
Narrow, fast-moving wind current in the upper troposphere
Position usually coincides in part with the regions of greatest storminess in the lower troposphere
Also called polar jet stream, because of the importance in moving cold, polar air.

37. The Atmosphere-weather: Jet Stream

38. Atmospheric-Oceanic Interactions: El Nino-Southern Oscillation (ENSO)
Normal conditions in eastern equatorial Pacific Ocean

39. Atmospheric-Oceanic Interactions: ENSO

40. Atmospheric-Oceanic Interactions: ENSO
El Nino-A warming of the surface water of the eastern and central Pacific Ocean, occurring every 4 to 12 years and causing unusual global weather patterns.
trade winds that usually push warm surface water westward weaken, allowing the warm water to pool as far eastward as the western coast of South America.

41. Atmospheric-Oceanic Interactions: ENSO

42. Atmospheric-Oceanic Interactions: ENSO

43. Atmospheric-Oceanic Interactions: La Nina
Cooling of the surface water of the eastern and central Pacific Ocean, causing similar, generally opposite disruptions to global weather patterns.
Trade winds blow more strongly than usual, pushing the sun-warmed surface water farther west and increasing the upwelling of cold water in the eastern regions.

44. Atmospheric-Oceanic Interactions: El Nino vs. La Nina

47. Typical vs. El Nino vs. La Nina
Winds off the western coast of equatorial South America blow east to west, pushing surface waters west.
Cooler deeper waters rise (upwelling) to replace moving surface water, bringing nutrients to the surface, increasing fish populations.
El Nino
Winds off the western coast of equatorial South America lessen, stop or start to blow west to east.
Warmer surface waters deepen as they “run into” western South America. Deep nutrients do not rise, decreasing fish populations.
La Nina
Winds off the western coast of equatorial South America strengthen, blowing east to west, pushing surface waters west.
Surface waters off of the west coast of equatorial South America cool due to increased upwelling. Increased fish populations.

48. Typical vs. El Nino vs. La Nina
Normal rainfall in western South America, southeastern Asia, eastern Africa, southeastern South America and southeastern U.S.
Normal rainfall in southern Africa, Australia, eastern South America, northwestern and northeastern Canada and U.S.
El Nino
Increased rainfall in western South America, southeastern Asia, eastern Africa, southeastern South America and southeastern U.S.
Less rainfall/drought in southern Africa, Australia, eastern South America, northwestern and northeastern Canada and U.S.
La Nina
Decreased rainfall in western South America, southeastern Asia, eastern Africa, southeastern South America and southeastern U.S. Increased tornadoes in the U.S.
More rainfall in southern Africa, Australia, eastern South America, northwestern and northeastern Canada and U.S.

49. Typical vs. El Nino vs. La Nina
Normal number of Atlantic and Pacific hurricanes
Normal temperatures in eastern Asia, northwestern Canada and U.S. and northeastern Canada and U.S.
El Nino
Fewer Atlantic and more Pacific hurricanes
Warmer temperatures in eastern Asia, northwestern Canada and U.S. and northeastern Canada and U.S.
La Nina
“Sometimes” more Atlantic and fewer Pacific hurricanes
Cooler winter temperatures in southeastern and southwestern U.S.
Warmer winter temperatures in north central U.S.

50. Don’t Forget the 5-Question Quick Quiz on Tuesday