基于卫星遥感的全球洋面降水暖云与非降水暖云的云参数差异

摘要

Data collected from quasi-synchronous Aqua/MODIS and CloudSat/CPR measurements were used to compare cloud parameters between precipitating and non-precipitating warm clouds over global oceans.The characteristics of cloud water vertical structure near cloud top,which were implied by the contrasts among the three cloud droplet effective radii (R16,R21,R37) retrieved from distinct nearinfrared channels of MODIS,were especially examined and their discrepancies between the two cloud categories were clarified.It is found that the global distribution of warm clouds has notable regional features.The valid range of most cloud properties are similar for precipitating and non-precipitating warm clouds,including cloud top temperature (CTT),optical thickness (COT),geometrical thickness,cloud droplet effective radius (Re),cloud water path (CWP).But there is still evident distinction between their averages,with the COT,Re,CWP of precipitating warm clouds significantly higher than non-precipitating ones.According to the statistics,the model of R37＜R21＜R16 corresponds to the maximum fraction of precipitating clouds.This suggests that cloud droplet size and cloud water mostly tend to monotonously increase downward when precipitation is generated from warm clouds.Such observational evidence reflects to some extent that multi-spectra based cloud retrievals are effective for detecting precipitation in warm clouds.%利用中分辨成像光谱仪(Aqua/MODIS)和云廓线雷达(CloudSat/CPR)两部星载仪器的准同步探测资料,分析了全球洋面暖云覆盖量和暖云降水频率的空间分布特征.并就暖云占优的多个中低纬海域,对降水暖云和非降水暖云的云微物理性质进行了对比,特别分析了由MODIS云滴有效半径(R16,R21,R37)相对大小所指示的云层顶部云水垂直结构在两类云之间的差异.研究结果表明,降水暖云与非降水暖云的云顶温度、光学厚度、云滴有效半径、云水路径等参数的有效范围接近一致,但均值存在明显差异.降水暖云的云顶高度显著偏高,其光学厚度、云滴有效半径、云水路径显著大于非降水暖云.针对6种云水垂直结构模态的初步统计结果显示,对应最大降水概率的模态为R37＜R21＜R16.该观测事实揭示了洋面暖云发展至降水阶段时,云层上部的云滴尺寸和云水含量多呈现为向下增长,该结果也反映了多光谱云参数反演资料在暖云降水识别中的潜在价值.