1. 1

2. 2

3. Atmospheric
Compositions

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. 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. Water Vapor
H2O

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. 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. Carbon Dioxide
CO2

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. Source: Le Quéré et al. 2012; Global Carbon Project 2012

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. Freon (CFC)
and Ozone (O3)

14. Freon-11
Freon-12
Refrigerators, air conditioners
Source:

15. Freons are greenhouse
gases but, more
importantly, they also
affect ozone…

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. Good ozone up high
Bad ozone near by

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. Global average

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. 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. Atmospheric
Structure
Air density?
Air pressure?
Air temperature?

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. 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. Vertical Profiles of Temperature
How do you think
the temperature
varies with height?

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. Tropopause

28. Why is a fire always going up?
Hot and lighter!
28

29. Why this balloon can carry so many people?
Fire hot air
Because the air density is less than surroundings

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. 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. Brick
Stable?