论大气二氧化碳温室效应的饱和度

ON THE SATURATION OF GREENHOUSE EFFECT DUE TO ATMOSPHERIC CARBON DIOXIDE

利用最新版本的大气分子吸收光谱资料HITRAN 2 0 0 0 ,用精确的逐线积分算法 ,计算了大气CO2 浓度变化后产生的辐射强迫。在此基础上 ,研究了CO2 温室效应的饱和度以及影响CO2 辐射强迫的各种因子。主要结论如下 :地面温度愈高 ,一般辐射强迫也愈大 ,但辐射强迫并不完全取决于地面温度 ,它还受大气温度廓线的强烈影响 ;研究的 6种模式大气中 ,吸收带重叠对热带大气的CO2 辐射强迫影响最大 ,对亚极冬季大气的影响最小 ;与长波辐射强迫相比 ,短波辐射强迫的贡献很小 ;CO2 的温室效应在 15 μm带中心等波段确实已经达到饱和 ,但在其它 (15 μm带两翼 ,10μm ,5 .2 μm带等 )波段远未达到饱和 。

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 CO 2, the saturation of greenhouse effect due to carbon dioxide and the spectral distribution of the saturation have been examined in the paper. The content and major conclusions of the paper are the follows: (1) Six model atmospheres: Tropical Atmosphere (TRP), Middle Latitude Summer Atmosphere (MLS), Middle Latitude Winter Atmosphere (MLW), Subarctic Summer Atmosphere (SAS), Subarctic Winter Atmosphere (SAW), and US Standard Atmosphere (USSTD), are chosen to study the effects of surface temperature and temperature profile on the radiative forcing. The results show that, in general, 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 radiative forcing due to carbon dioxide includes both of the contributions from the short wave and long wave. The solar zenith angle, duration of daylight and the solar irradiance on the top of the atmosphere are calculated in order to compute the short wave radiative forcing for each model atmosphere. Compared with the long wave radiative forcing, the solar short wave radiative forcing is very small. (3) Effects of overlapping of the absorption bands on the radiative forcing have been examined for different model atmosphere. We found that the band overlapping has significant effect on the radiative forcing and it depends on the model atmosphere. The effect is the largest for the TRP atmosphere and smallest for the SAW atmosphere. (4) The saturation of greenhouse effect due to carbon dioxide and its spectral distribution are studied through calculating respectively the radiative forcing due to two times, four times and eight times of present concentration of atmospheric carbon dioxide. The results show that the greenhouse effect due to carbon dioxide is saturated in the center of CO 2 15μm band, indeed, but it is never saturated and will not be saturated in the near future for the wings of 15μm band and the other bands.