3. Origin of Earth’s Atmosphere Early Earth was HOT! Why? Accretion; Radioactive decay of elements Consequences - Constant volcanism, surface temperature too high for liquid water or life as we know it, molten surface or thin, unstable basaltic crust. Cooling led to: Condensation & accumulation of surface water Changing atmosphere due to volcanic out-gassing The right conditions for the evolution of life Source: http://www.ux1.eiu.edu/~cfjps/1400/atmos_origin.html

4. 1 st Atmosphere Composition - H 2, He Lost to space early in Earth's history because: Earth's gravity is not strong enough to hold lighter gases Earth still did not have a differentiated core (solid inner/liquid outer core) which creates Earth's magnetic field (magnetosphere = Van Allen Belt) which deflects solar winds. Once the core differentiated the heavier gases could be retained

5. 2 nd Atmosphere Produced by volcanic out-gassing. H 2 O, CO 2, SO 2, CO, S 2, Cl 2, N 2, H 2 and NH 3 (ammonia) and CH 4 (methane) No free O 2 at this time Ocean Formation - As the Earth cooled, H 2 O produced by out-gassing could exist as liquid in the early Archean, allowing oceans to form.

6. Addition of O 2 Photochemical dissociation - breakup of water molecules by UV radiation Produced O 2 levels approx. 1-2% current levels At these levels O 3 (Ozone) can form to shield Earth surface from UV Photosynthesis – CO 2 + H 2 O + sunlight  glucose + O 2 O 2 produced by cyanobacteria, and eventually higher plants

7. Present Composition 78% Nitrogen 21% Oxygen 1% Other trace gases

8. Layers of the Atmosphere Caused by temp. differences These differences result from how solar energy is absorbed as it moves through the atmosphere

9. http://www.aerospaceweb.org/question/atmosphere/atmosphere/layers.gif

10. 4 Main Layers of the Atmosphere http://www.epa.gov/apti/course422/images/fig-1.gif

11. http://www.greenfacts.org/images/glossary/stratosphere-troposphere.jpg

14. Troposphere Closest to Earth Nearly all weather occurs here Almost all H 2 O vapor and CO 2 Temp. decreases with altitude because air in this layer is heated from below by thermal energy that is re-radiated from Earth’s surface

15. Tropopause Upper boundary of the troposphere Jet stream - Varies with latitude & seasons - 250 mph - East wind

16. Stratosphere 16 – 50 km Ozone layer is here Temp. increases because air is heated from above by absorption of solar radiation by ozone Jets fly here to avoid turbulence Stratopause - upper boundary

17. Ozone Layer Ozone is made of 3 atoms of oxygen (O 3 ) ≈ 2-3 mm thick if it were at sea level Purpose - absorbs harmful UV radiation from the Sun

18. Mesosphere 50 – 85 km Temp. decreases as altitude increases Mesopause - Upper boundary Avg Temp. = - 90 o C COLDEST layer in the atmosphere Meteors begin to disintegrate here

19. Red Sprite

20. Sprites

21. Sprites

22. Blue Jets

23. E.L.Ves. Emission of Light and Very low frequency perturbations

24. Thermosphere 90 km ~ 1000 km Space begins here (~100 km) Temp. increases as altitude increases Can’t read temp. with a thermometer because air particles are too far apart Space Shuttle & ISS orbit here Ionosphere is the lower region Aurora occur here

25. Exosphere End of the atmosphere Almost a vacuum Where light elements escape Earth’s gravity

27. http://curriculum.calstatela.edu/courses/builders/lessons/less/les3/les3gifs/layers.gif

31. Temperature A measure of the kinetic energy of the molecules of a substance

32. Methods of Heat Transfer Conduction – direct transfer Convection – bulk movement of particles Radiation – electromagnetic waves

33. Where does radiation go? 25% penetrates Earth’s atmosphere 20% absorbed by the atmosphere 30% scattered back into space (albedo)

34. Albedo Varies due to  Cloud cover  Particulate matter (dust, pollen, ash, etc.)  Sun’s angle  Surface (water vs. land)

35. Differential Heating Earth’s surface is heated unevenly due to:  Geographic position (latitude)  Land vs. Water  Altitude  Ocean currents  Cloud cover  Albedo

36. Humidity The amount of water vapor in the air 90% of water vapor comes from oceans (evaporation) The warmer air is, the more water vapor it can hold

37. Dew Point The temp. at which water vapor begins to condense If the dew point and air temp. are the same, the following will form:  At ground level = dew or frost  Just above ground = fog  Higher levels = clouds

38. Relative Humidity The amount of water vapor in the air expressed as a percentage of the amount required to saturate the air at the current temp. % R.H. = Actual absolute humidity x 100 Maximum absolute humidity

39. Psychrometer Used to measure humidity Made with 2 thermometers - Dry bulb Measures air temp. - Wet bulb Cooler than dry bulb Uses evaporation to measure temp. - Wet bulb depression – difference between dry & wet bulb temps.

41. Particulates Tiny, solid particles Volcanic dust Ash f/ fires Microscopic organisms Mineral particles f/ the soil Pollen f/ plants Particles f/ meteors Salt f/ the ocean Can be suspended for mo’s or yrs

42. Fly ash from burning wastes http://images.google.com/imgres?imgurl=http://www.chemsoc.org/exemplarchem/entries/2002/Air%2520pollution%2520- %2520Smith%2520%26%2520Kirsop/particulates.gif&imgrefurl=http://www.chemsoc.org/exemplarchem/entries/2002/Air%2520pollution%2520- %2520Smith%2520%26%2520Kirsop/dogs16.htm&h=251&w=332&sz=62&hl=en&start=1&tbnid=jq- gUdKJKpbV4M:&tbnh=90&tbnw=119&prev=/images%3Fq%3Dparticulates%26svnum%3D10%26hl%3Den%26rls%3DTSHA,TSHA:2006-08,TSHA:en

43. Air Pollutants Any substance that is in the atmosphere & is harmful to people, animals, plants or property Main source is burning of fossil fuels These release harmful substances SO 2, hydrocarbons, N oxides, CO & Pb into the air

44. Pollutants http://www.greenfacts.org/images/glossary/secondary-pollutants.jpg

45. http://www.nuigalway.ie/ccaps/research_atmospheric_composition.html

46. http://www.windows2universe.org/earth/Atmosphere/ozone_hole.html

47. Breaking Down the Ozone Layer CFC’s (chlorofluorocarbons) break down the ozone layer They used to be used in refrigerators, air conditioners & exhaust compounds

48. www.theozonehole.com

49. Temperature Inversions When a layer of warm air is on top of cool air This can trap polluted air beneath Topography can make it worse Smog occurs b/c of the pollutants & lack of circulation

50. Temperature Inversion http://www.epa.qld.gov.au/images/environmental_management/air/warm_air_inversion.jpg

51. http://www.virtual-lakes.co.uk/DerLatriggInversion.jpg

52. http://www.weatherquestions.com/temperature_inversion.jpg

53. How to Control Smog Prevent the release of pollutants Passage of laws Community awareness Personal responsibility

54. http://davidk.scelerat.com/images/smog-med.jpg

55. Atlanta, GA http://gallery.bostonradio.org/2004-11/atlanta/100-02527-med.jpg