温室气体吸收带重叠对CO_2红外辐射效应的影响

The Overlapping Effect of Greenhouse Gases Absorption Bands on CO_2 Thermal Radiative Effect

利用精确的逐线积分模式,研究了大气主要温室气体H2O、CO2、O3、N2O和CH4吸收带重叠对红外冷却率的影响。同时,通过CO2浓度加倍的敏感性试验,详细讨论了重叠效应对CO2辐射效应的影响。结果表明:气体吸收带重叠对大气红外辐射计算具有重要的影响。在这5种大气主要的吸收气体中,N2O和CH4的重叠效应对总冷却率影响很小,在实际应用中可以忽略两者的重叠作用,采用近似方法处理其贡献。重叠效应对CO2辐射效应影响的总趋势是减弱由于其浓度增加而导致的温室效应的增强,主要贡献来自于CO215μm带的两翼,以及以960 cm-1和1064 cm-1为中心的次级弱吸收区。在垂直方向上,重叠效应主要表现在减弱了地表大气的增温强度,并使对流层大气由原来的冷却作用转变为增暖作用,而对平流层大气的影响很小。此外,由于大气H2O含量的变化,重叠效应还表现出明显的季节性和纬度变率。

The effect of overlapping of atmospheric H2O,CO2,O3,N2O,and CH4 absorption bands on the total thermal cooling rates and the radiative perturbation due to the doubling CO2 abundance are investigated using an exact line-by-line integration algorithm.It is found that the overlapping effect plays an important role on the calculation of thermal cooling rates.Among the five main infrared absorbers,the overlapping effect of N2O and CH4 can be neglected as their little contribution.The influence of overlapping effect on the CO2 thermal radiative is to decrease the enhanced greenhouse effect due to increased absorber announces which are mainly contributed by the 15-μm CO2 band wings and the secondary weaker bands centred at 960 cm-1 and 1064 cm-1.In vertical,overlapping effect has slight influence on the radiative perturbation in stratosphere,but plays a significant role in troposphere and surface.The net effect of the overlapping absorption is to transform the troposphere from cooling to warming,and to decrease the strength of surface warming caused by CO2 increase.Additionally,overlapping effect exhibits strong seasonal and latitudinal variations due primarily to changes in H2O concentration.