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# Distribution of Gases in the Atmosphere

Distribution of Gases in the Atmosphere. Most gases are well mixed and distributed evenly throughout the lowermost 100 km of the atmosphere. Examples: O 2 , N 2 , Ar, CO 2 , freons Gases with short lifetimes are not well-mixed. Example: O 3. Structure of the Atmosphere.

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## Distribution of Gases in the Atmosphere

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1. Distribution of Gases in the Atmosphere • Most gases are well mixed and distributed evenly • throughout the lowermost 100 km of the atmosphere. • Examples: O2, N2, Ar, CO2, freons • Gases with short lifetimes are not well-mixed. • Example: O3

2. Structure of the Atmosphere Pressure = force per unit area (exerted by a gas or liquid on a surface) At sea level, P = 1 atmosphere = 1.013 bar (or 1013 mbar) Pressure decreases away from the Earth’s surface. The air becomes “thin” at high elevations.

3. The Barometric Law • Pressure declines exponentially with altitude • Thus, it forms a (nearly) straight line when plotted on a log scale 

4. Pressure vs. Altitude 100 80 Altitude (km) 60 40 20 10-3 1 103 Pressure (mbar)

5. Pressure vs. Altitude 100 80 Pressure decreases away from the Earth’s surface. Altitude (km) 60 40 20 10-3 1 103 Pressure (mbar)

6. Temperature vs. Altitude 100 80 Altitude (km) 60 40 20 200 250 300 (-73 -23 +27 oC) Temperature (K)

7. Temperature vs. Altitude 100 80 Altitude (km) 60 40 20 Temperature decreases 200 250 300 Temperature (K)

8. Temperature vs. Altitude 100 80 Altitude (km) 60 40 20 Troposphere 0-10 km Temperature decreases 200 250 300 Temperature (K)

9. Temperature vs. Altitude 100 80 Altitude (km) 60 Temperature increases 40 20 Troposphere 0-10 km 200 250 300 Temperature (K)

10. Temperature vs. Altitude 100 80 Altitude (km) 60 Temperature increases Stratosphere 10-50 km 40 20 Troposphere 0-10 km 200 250 300 Temperature (K)

11. Temperature vs. Altitude 100 80 Mesosphere 50-90 km Temperature decreases 60 Stratosphere 10-50 km 40 20 Troposphere 0-10 km 200 250 300 Temperature (K)

12. Temperature vs. Altitude + 1000 oC Thermosphere 90 + km 100 Temperature increases 80 Mesosphere 50-90 km 60 Stratosphere 10-50 km 40 20 Troposphere 0-10 km 200 250 300 Temperature (K)

13. Troposphere heated by convection turbulent, mixed contains all weather (wind, rain, clouds, etc.) water is important in this region Stratosphere not well mixed, or “stratified” cold at base, warmer in upper region ozone present ozone heats upper region by absorbing uv radiation

14. + 1000 oC 100 80 60 ozone Stratosphere 10-50 km 40 20 water Troposphere 0-10 km 200 250 300 Temperature (K)

15. Atmospheric Structure

16. Quiz Why is it colder at high altitudes in the troposphere? Answer- As air expands it looses energy by doing work. The loss of energy results in lower temperatures?

17. Quiz Why do temperatures rise in the stratosphere? Temperatures rise because oxygen (O2) and ozone (O3) absorb the sun’s light, (uv radiation).

18. Simple Circulation

19. Surface Circulation

20. Coriolis Effect

21. Coriolis Effect

22. Surface Circulation

23. Representative ocean temperature profile

24. Representative Ocean DensityPprofile

25. Simple model: Ocean is two boxes Warm upper box Deep cold box

26. What happens to CO2 after it dissolves in ocean? Carbonic acid CO2 +H20 H2CO3 H2CO3 + CO3-2 HCO3- + H+ carbonate bicarbonate Carbonate neutralizes the CO2

27. The Atlantic Conveyor

28. How long does it take to exchange the deep water with the surface water? Approx. 1,000 years How do we know this? C-14 measurements

29. Simple model: Ocean is two boxes Atmospheric CO2 rapid exchange H2CO3 + CO3-2 HCO3- + H+ Warm upper box Slow mixing or exchange Deep cold box

30. What is the ocean’s capacity to neutralize CO2? For the surface ocean: Concentration of carbonate times volume of surface ocean For the whole ocean: Concentration of carbonate times volume of surface ocean Result: Ocean water can’t neutralize all CO2 tha may be emitted.

31. Additional neutralizing Capacity Ocean sediments; CaCO3 +H2CO3 Ca+2 + 2HCO3- What are these? CaCO3 from coccolithophorids and foraminifera.

32. Sediment Map showing abundant carbonate sediments

33. Biology is also important Photosynthesis here by phytoplankton CO2 + H2O CH20 + O2 Warm upper box Organic debris sinks Decomposition via bacterial respiration CH20 + O2 CO2 + H2O Deep cold box

34. Where is the missing CO2? Only half of the CO2 released by human activity is still in the atmosphere. There is evidence that approx. half of the missing CO2 has dissolved into the ocean and the other half has been incorporated into the biosphere.

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