淮河流域混合云频率、云高和含水量的毫米波云雷达资料分析

Analysis on millimeter-wave cloud radar data of the occurrence frequency,the top height and the liquid water path of mixed phase clouds over Huai River basin

本文选用2007年1月—2010年2月的Cloud Sat卫星94 GHz探测资料（2B-GEOPROF）对淮河流域混合云出现频率、云高以及含水量分布规律进行了研究。研究结果表明：（1）混合云出现频率和云高具有显著的季节性变化特征,均表现为夏季值高、冬季低;（2）Cloud Sat 2B-CWC-RO反演产品在假设混合云冰水混合比与云内温度（-20-0℃）成线性关系条件下反演的液态水含量（LWP）与地面观测值相差较大,本文利用冰水混合比与云内温度成指数函数关系反演的LWP更接近地面观测值;（3）反演的LWP具有明显的季节分布特征,其季节平均值夏秋季高、春冬季低。混合云随着LWP值的增加,其对应的雷达反照率因子范围和出现的高度层越来越集中,混合云在对流层中下层的出现频率随LWP的增加而增多,出现频率高值区及其分布的高度层也具有明显的季节性特征,并与混合云零度层高度有密切关系。

By using the Cloud Sat data（ 2B-GEOPROF） provided by 94 GHz spaceborne radar from January 2007 to February 2010,the occurrence frequency,top height and the liquid water path（ LWP） of the mixed phase clouds over Huai River basin were studied. Results show that：（ 1） both of the occurrence frequency and top height of mixed phase clouds show seasonal distribution characteristics,which are higher in summer and lower in winter;（ 2） the LWP provided by the Cloudsat Level 2B Standard Data Products（ 2B-CWC-RO） under the assume that the mixture ratio of ice and liquid water has linear relation with the temperature of cloud（- 20 ℃- 0 ℃） is remarkably different from the ground observation,however,the LWP retrieved by the exponential relationship between the mixture ratio of ice and liquidwater and the temperature of cloud is much closer to the ground observation;（ 3） the retrieved LWP has obvious seasonal distribution characteristics,which show higher in summer and lower in winter. With the LWP of the mixed phase clouds increasing,the range of radar reflectivity and their altitude are more and more concentrated. The mixed phase clouds＇ occurrence frequency in lower troposphere increases with the LWP value increasing; the maximum value of corresponding radar reflectivity has remarkable seasonal characteristics,which is dependent on the height of 0 ℃ layer of mixed phase clouds.