基于COSMIC掩星探测资料的云底高反演研究

本文基于相对湿度廓线进入云层时的突变实现云底高反演的思想,采用2008年11月至2009年1月的COSMIC掩星湿空气数据反演全球云底高度,并与探空资料反演结果进行对比分析,得出以下重要结论:(1)当温度－40 ℃

Research of cloud-base height retrieval based on COSMIC occultation sounding data

Based on the idea of retrieving cloud-base height by using the mutation of relative humidity profile when it comes into cloud,this paper gets information of cloud-base height by using COSMIC wet air data from November 2008 to January 2009,and after comparing with the results retrieved from radiosonde data,it acquires the following important conclusions:(1)When the temperature of cloud layer is between 0 and-40 Celsius Degree,this paper retrieves the cloud-base height when cloud phase is respectively thought as liquid cloud or ice cloud,and finds that it may fail to detect high cloud and multilayer cloud if cloud phase is considered as pure liquid;(2)COSMIC gets worse cloud-base height results for low cloud and better ones for high cloud and multilayer cloud,and its retrieval results are generally greater than radiosonde′s;(3)To further analyze the differences of retrieval results between COSMIC and radiosonde when they both detect cloud,this paper discusses the retrieval results respectively as their cloud-layer numbers are equal or not.When the cloud-layer numbers are equal,the differences are larger in low-latitude regions and for the single layer cloud by calculating their mean and standard deviation,but they have consistent results for three-layer and four-layer cloud.When the numbers are different,some single layer clouds from COSMIC split up into multilayer clouds in the radiosonde results,which leads to the great differences between them.