气溶胶光学厚度、类型及廓线对CO2反演的敏感性分析

位于1.6和2.06 μm附近的短波红外波段可用于探测低层大气CO²信息,然而除大气分子(主要是CO²)吸收外,大气分子散射、气溶胶和云散射也是限制这些波段的卫星测量信号的主要因素,因此气溶胶光学参数及其垂直分布也必然制约着GOSAT(Greenhouse Gases Observing Satellite)CO²的反演精度。利用正演模式DISORT分析气溶胶光学厚度(AOD)、类型以及廓线对CO²反演精度的敏感性,旨在提高CO²反演精度。结果表明:①不同类型气溶胶AOD增大对CO²柱总量的影响各不相同,且CO²柱总量变化量的变化趋势也不相同,这取决于气溶胶的散射相函数与单次散射反照率的大小;②气溶胶类型变化会导致CO²柱总量变化,且这种变化随着AOD增大而增大;③对于满足指数分布的沙尘气溶胶,标高的低估会导致反演的CO²柱总量偏大,而气溶胶的集中分布导致反演的CO²柱总量偏小,且气溶胶层越高,反演的CO²柱总量越小。

Sensitivity Studies for CO2 Inversion of Aerosol Optical Depth,Type and Profile

Short-Wave InfraRed(SWIR)Band located at 1.6 μm and 2.06 μm can be used to detect the CO² information at low atmosphere.Apart from that of atmospheric compositions(mostly CO²),satellites measurements in the SWIR are also influenced by scattering of atmospheric molecular,aerosols and clouds.Therefore the aerosol and its vertical distribution could reduce the accuracy of total column CO² from the GOSAT.In order to improve the accuracy,the sensitivities of retrieval algorithm with AOD,types and its profiles have been analyzed by a forward radiative transfering model\|DISORT.The results show that:①The impact of AOD ,depending on the phase function and single scattering albedo,has different behaviour for different aerosol types,and the variation CO² column amount with the increase of AOD is also different;②When aerosol type changes,the CO² column amount varies,and this variation increases with AOD;③For dust aerosols,of which the vertical distribution decrease exponentially with height,indexed by a scale height,underestimation of scale height will result in overestimated CO² column amount,while aerosols concentrated within a limited height,underestimation of aerosol height will result in underestimated CO² column amount,and the higher the aerosol layer,the smaller of CO² column amount will be  derived.