Geoscience Reference
In-Depth Information
The atmosphere is a mixture of gases with constant proportions of up to 80km or more. The
exceptions are ozone, which is concentrated in the lower stratosphere, and water vapor in the lower
troposphere. The principal greenhouse gas is water vapor. Carbon dioxide, methane and other trace
gases have increased significantly since the Industrial Revolution, especially in the twentieth
century, due to the combustion of fossil fuels, industrial processes, and other anthropogenic
effects, but larger natural fluctuations occurred during the geologic past.
Reactive gases include nitrogen and sulfur and chlorine species. These play important roles in
acid precipitation and ozone destruction. Acid precipitation (by wet or dry deposition) results from
the reaction of cloud droplets with emissions of SO 2 and NOx. There are large geographical
variations in acid deposition. The processes leading to the destruction of stratospheric ozone are
complex, but the roles of nitrogen oxides and chlorine radicals are highly important in causing polar
ozone holes. Aerosols in the atmosphere originate from natural and anthropogenic sources and
they play an important but complex role in climate.
Air is highly compressible, so that half of its mass occurs in the lowest 5km, and pressure
decreases logarithmically with height from an average sea-level value of 1013mb. The vertical
structure of the atmosphere comprises three relatively warm layers - the lower troposphere, the
stratopause and the upper thermosphere - separated by a cold layer above the tropopause (in the
lower stratosphere), and the mesopause. The temperature profile is determined by atmospheric
absorption of solar radiation, and the decrease of density with height.
What properties distinguish the different layers of the atmosphere?
What differences would exist in a dry atmosphere compared with the real atmosphere?
What role is played by water vapor, ozone, carbon dioxide, methane and CFCs in the radiation
balance of the atmosphere?
Given the strong pressure gradient upward from the surface, why is there no large-scale upward
flow of air?
REFERENCES AND FURTHER
READING
13), J. Wiley & Sons, Chichester, 528pp.
[Important early overview]
Bolin, B., Döös, B. R., Jäger, J. and Warrick, R. A.
(eds) (1986) The Greenhouse Effect, Climatic
Change, and Ecosystems (SCOPE 29), J. Wiley
& Sons, Chichester, 541pp.
Bridgman, H. A. (1990) Global Air Pollution:
Problems for the 1990s, Belhaven Press,
London, 201pp. [Broad survey of air pollution
causes and processes by a geographer; includes
greenhouse gases]
Books
Andreae, M. O. and Schimel, D. S. (1989) Exchange
of Trace Gases Between Terrestrial Ecosystems
andtheAtmosphere,J. Wiley& Sons, Chichester,
347pp. [Detailed technical treatment]
Bolin, B., Degens, E. T., Kempe, S. and Ketner, P.
(eds) (1979) The Global Carbon Cycle (SCOPE
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