利用掩星资料分析东亚地区云厚的分布特征

利用2007年1月至2009年1月COSMIC掩星湿空气数据,基于相对湿度廓线出入云层时发生突变反演云边界高度的思想,统计分析了东亚地区云厚的分布特征。结果表明,掩星最低探测高度集中在3km以下,主要影响部分中云和低云云厚的反演。云发生概率沿纬度和经度方向呈现不同的分布特征,各类云概率随高度也有不同的变化规律。东亚地区所有云的平均厚度为1.78km,其中单层云和顶层云分布相似,双层云与其他云层的地理差异不大,单层云在春秋季分布相对均匀,而在夏冬季差异较大。夏季和冬季顶层云云顶高与云厚的二维频率分布各异,主要在于夏季有更多云体较厚且位于对流层上部的高云存在。

Characteristics Analysis of Cloud-Layer Thickness in East Asia Using Occultation Data

Based on the idea that getting cloud boundary height by using mutation of relative humidity profile when it comes into or out of clouds,we obtain the statistical characteristics of cloud-layer thickness in East Asia by using COSMIC occultation wet-air data from Jan.2007 to Jan.2009.The results show that minimum detecting altitude of COSMIC is lower than 3 km height,which mainly affects the retrieval of cloud-layer thickness of part middle-and low-level clouds.Occurrence frequencies of clouds along the direction of latitude and longitude show different distribution characteristics,and as altitude increases,frequencies of various types of clouds also have different variation regularity.Average thickness of all clouds in East Asia is 1.78 km,and single-layer cloud has the same distribution with highest-layer cloud,and two-layer and other-layer clouds have similar geographic distribution.Single layer cloud is relatively uniform in spring and autumn but the differences in summer and winter are relatively large.Two-dimensional frequency distributions of cloud-top height and layer thickness of highest-layer cloud in summer and winter are different,which mainly indicates that there are more thicker high clouds existing in upper troposphere in summer than in winter.