On The Radiative Forcing And The Saturation Of Greenhouse Effect Due To Atmospheric Carbon Dioxide

The objective of this paper is to study the saturation of greenhouse effect due to carbon. dioxide and the spectral distribution of the saturation. Using HITRAN 2000, the updated absorption line data of atmospheric molecules, and an exact line-by-line algorithm, we have calculated the radiative forcing (in turn the greenhouse effect) due to the changes in concentration of atmospheric carbon dioxide. Based on the comparison among radiative forcing resulted from various concentration of atmospheric CO2, the saturation of greenhouse effect due to carbon dioxide and the spectral distribution of the saturation have been examined.The content of the paper is composed of 4 parts:1. The effects of surface temperature and temperature profile on the radiative forcing. Six model atmospheres are chosen in this paper: Tropical Atmosphere (TRP), Middle Latitude Summer Atmosphere (MLS), Middle Latitude Winter Atmosphere (MLW), Subarctical Summer Atmosphere (SAS), Subarctical Winter Atmosphere (SAW), and U.S. Standard Atmosphere (USSTD). The results show that, ingeneral, the radiative forcing is larger when the surface temperature is higher. However, the radiative forcing depends not only on the surface temperature but also the atmospheric temperature profile.2. The calculation of the solar radiation. The radiative forcing includes both of short-wave and long-wave radiative forcing. The zenith angle, duration of daylight and the total solar radiation on the top of the atmosphere are calculated in order to compute the short-wave radiative forcing for each model atmosphere.3. Effects of overlapping of the absorption bands on the radiative forcing have been examined for different model atmosphere. We found that the overlapping effect is the largest for the TRP atmosphere and smallest for the SAW atmosphere.4. The saturation of greenhouse effect due to carbon dioxide. The saturation of greenhouse effect due to carbon dioxide is studied through calculating respectively the radiative forcing due to two times, four times and eight times concentration of atmosphere carbon dioxide. The results show that the greenhouse effect due to carbon dioxide is saturated in the center of 15 u m band of CO2, indeed, but it is never saturated and will not be saturated in the near future for the wings of 15 v m band and the other bands.