particularly effective at absorbing counterradiation. The amount of water vapor in the atmosphere is a direct response to temperature. Other long wave-absorbing gases can be produced by human activity. Carbon dioxide and certain other trace gases (such as methane, nitrous oxide, and chlorofluorocar-bons) can potentially upset the long wave exchanges involved in the Earth's energy balance. Such deviations can lead to changes in the average global temperature. Potential consequences of an escalating amount of these atmospheric gases include a growing proportion of outgoing long wave radiation being "trapped" in the atmosphere, leading to an increase in the Earth's temperature.
Clouds serve as very effective absorbers of outgoing long wave radiation. This, in turn, affects surface and near-surface temperatures. The presence of clouds in a nighttime sky results in warmer temperatures than a cloudless one. In the absence of incoming short wave radiation, only long wave exchanges occur at night. With clouds trapping much of the outgoing long wave, substantial amounts are redirected back toward the surface. This increases the near-surface temperatures. Similarly, the lack of clouds leads to greater amounts of long wave radiation escaping the Earth-atmosphere system to space.
SEE ALSO: Albedo; Radiation, Microwave; Radiation, Short Wave; Radiative Feedbacks.
BIBLIOGRAPHY. C.D. Ahrens, Meteorology Today (Thompson Brooks/Cole, 2007); T.R. Oke, Boundary Layer Climates (Routledge, 1987); P.J. Robinson and Ann Henderson-Sellers, Contemporary Climatology (Prentice Hall, 1999).
Petra A. Zimmermann
Ball State University
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