用TRMM/TMI估算HUBEX试验区的云中液态水
ESTIMATION OF CLOUD LIQUID WATER OVER THE HUBEX AREA USING TRMM/TMI
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摘要: 文中应用热带降雨测量卫星微波成像仪的微波遥感资料反演云中液态水。由于微波成像仪85.5 GHz通道对云中液态水非常敏感,通过离散纵坐标矢量辐射传输模式,运用迭代的方法可以有效地反演出陆地上空非降水云中的液态水路径。在淮河流域能量与水分循环试验中,分别运用微波成像仪85.5 GHz垂直极化单通道和微波成像仪85.5 GHz极化亮温差两种方法来估算陆地上空的云中液态水路径,反演结果与地基微波辐射计的测量结果是较为一致的。当地表比辐射率或地表温度误差较大时,用极化亮温差法估算云中液态水路径相对较好,尤其是对于低云,因为该方法对地表温度不敏感。Abstract: The ability of the tropical rainfall measuring mission microwave imager (TRMM/TMI) for cloud liquid water (CLW) retrieval has been demonstrated in this study. Due to the great sensitivity of the TMI 85.5 GHz channels to CLW,the liquid water path (LWP) of nonprecipitating clouds over land can be successfully estimated by using the vector discrete ordinate radiative transfer(VDISORT) model based on the iteration algorithm. Both the vertical-polarized 85.5 GHz single-channel method and the polarization-difference of 85.5 GHz method were applied for the LWP estimates over land regions during the Huaihe River Basin Energy and Water Cycle Experiment (HUBEX) in China. The retrieval results show reasonable agreement with the ground-based microwave radiometer measurements. When the surface emissivity or skin temperature is difficult to be made sure, the polarization-difference method shows advantages of providing estimates of LWP,especially for low clouds because of its extremely insensitiveness to the surface skin temperature.