Lecture4 sep16-bb

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Lecture4 sep16-bb

  1. 1. 1
  2. 2. 2
  3. 3. Atmospheric Compositions
  4. 4. Composition of the Atmosphere Air is composed of a mixture of gases: Gas N2 O2 Ar concentration (%) 78 21 0.9 99.9% Major constituents
  5. 5. Composition of the Atmosphere Air is composed of a mixture of gases: Gas greenhouse gases concentration (%) N2 O2 Ar H2O CO2 CH4 N2O O3 78 21 0.9 variable 0.037 Minor constituents
  6. 6. Water Vapor H2O
  7. 7. Water? Or water vapor? Water vapor  H2O  Invisible  The most abundant greenhouse gas  Variable, why?  Only substance is naturally in three phases: solid, liquid, and a gas solid liquid gas
  8. 8. Composition of the Atmosphere Air is composed of a mixture of gases: Gas greenhouse gases concentration (%) N2 O2 Ar H2O CO2 CH4 N2O O3 78 21 0.9 variable 0.037 Minor constituents
  9. 9. Carbon Dioxide CO2
  10. 10. The dashed land-use change line does not include management-climate interactions The land sink was a source in 1987 and 1998 (1997 visible as an emission) Source: Le Quéré et al. 2012; Global Carbon Project 2012
  11. 11. Source: Le Quéré et al. 2012; Global Carbon Project 2012
  12. 12. Composition of the Atmosphere Air is composed of a mixture of gases: Gas greenhouse gases concentration (%) N2 O2 Ar H2O CO2 CH4 N2O O3 78 21 0.9 variable 0.037 Minor constituents
  13. 13. Freon (CFC) and Ozone (O3)
  14. 14. Freon-11 Freon-12 Refrigerators, air conditioners Source:
  15. 15. Freons are greenhouse gases but, more importantly, they also affect ozone…
  16. 16. Ozone (O3) production • Concentrated in stratosphere (10-50km) • Produced by absorbing UV radiation through the ozone-oxygen cycle: O2 + UV  O + O, O + O2  O3 • Ground-level ozone (troposphere) is created when intense sunlight reacts with nitrogen oxides (NOx) and volatile organic compounds (VOCs), which mainly come from vehicles, power plants, and industrial facilities. VOC + NOx + + = ozone
  17. 17. Good ozone up high Bad ozone near by
  18. 18. Ozone (O3) destruction CFCs: float up to stratosphere and constantly react with O3 to form ClO and O2: Cl + O3  ClO+ O2 ClO + O  Cl +O2 Scientists estimate that one chlorine atom can destroy 100,000 "good" ozone molecules. The Antarctic ozone hole, seen from space, Sept. 16, 2000. More Dobson units = more ozone. Image from NASA/TOMS CFCChlorofluorocarbons CIO chlorine monoxide Figure 1-6 Simultaneous measurements of ozone (O3) and chlorine monoxide (CIO) made from a NASA aircraft as it flew into the Antarctic ozone hole in
  19. 19. Global average
  20. 20. See The Earth System, ed. 2, of 1-6 Figure 1-6 Simultaneous measurementsFig. ozone (O3) and chlorine monoxide (CIO) made from a NASA aircraft as it flew into the Antarctic ozone hole in September 1987.
  21. 21. The Nobel Prize in Chemistry 1995 Paul J. Crutzen Max-Planck-Institute Mario J. Molina F. Sherwood Rowland MIT UC Irvine Paul Crutzen, Mario Molina and Sherwood Rowland have all made pioneering contributions to explaining how ozone is formed and decomposes through chemical processes in the atmosphere. Most importantly, they have in this way showed how sensitive the ozone layer is to the influence of anthropogenic emissions of certain compounds. The thin ozone layer has proved to be an Achilles heel that may be seriously injured by apparently moderate changes in the composition of the atmosphere. By explaining the chemical mechanisms that affect the thickness of the ozone layer, the three researchers have contributed to our salvation from a global environmental problem that could have catastrophic consequences.
  22. 22. Atmospheric Structure Air density? Air pressure? Air temperature?
  23. 23. Vertical Profiles of Density The density = Mass Volume The density of air decreases with height. Density profile cannot be used to describe atmospheric structure!
  24. 24. Atmospheric Pressure Pressure = force per unit area Atmospheric Pressure at Sea Level: 1013.25 millibars (mb) Pressure profile cannot be used to describe atmospheric structure!
  25. 25. Vertical Profiles of Temperature How do you think the temperature varies with height?
  26. 26.  Temperature decreases with height. lapse rate (6.5 oC/km) top of troposphere  the tropopause higher is summer, lower in winter tropopause is proportional to mean tropospheric temperature  where all the weather occurs Unstable 90% of all the gases on Earth is in this layer
  27. 27. Tropopause
  28. 28. Why is a fire always going up? Hot and lighter! 28
  29. 29. Why this balloon can carry so many people? Fire hot air Because the air density is less than surroundings
  30. 30. Stable State example: if you push the rock A along either side of the hill and then let go, it will return to its original position
  31. 31. Unstable State example: if the rock rests on the top of the hill, a slight push will set it moving away from its original position
  32. 32. Brick Stable?

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