基于CloudSat卫星观测资料的辽宁省不同天气系统影响下云系垂直结构特征

Characteristics of Cloud Vertical Structure Under Different Synoptic Systems in Liaoning Province Based on CloudSat Observation

为区分不同天气系统影响下云垂直结构的差异,从而为人工增雨作业提供参考,对2004-2014年辽宁省进行人工增雨作业期间,500、850 hPa以及地面的天气形势进行了统计,利用CloudSat卫星观测资料对筛选的出现频率≥2次·a-1的系统配置下的云垂直结构进行分析,并研究了典型系统影响下的作业云系垂直结构特征。根据系统配置差异,2004-2014年间影响辽宁省的共有225次过程,可划分为17种配置类型,其中典型天气系统四种,分别为西风槽-切变线-冷锋(CF型)、西风槽-低涡-蒙古气旋(MCW型)、西风槽-低涡-南方气旋(SC型)和低涡-低涡-蒙古气旋型(MCV型)。对四种典型天气系统影响下的云垂直结构分析发现,不同天气系统影响下云层均以单层云为主。SC影响下的云层发展较为旺盛,云底较低而云顶较高,云层深厚。MCW影响下的云层云底高度较高,云层较薄。不同天气系统影响下的云夹层厚度大多(>50%)在1 km以下,而且随着云层数目增加,低于1 km的云夹层所占的比例增加。将云底高度≤2 km且云厚≥2 km视为作业云系,发现有云条件下,SC型符合条件的作业云系最多(59.7%),而MCW型影响下最少(14.5%)。作业云系以单层低冷云为主,单层低冷云的云底高度低于1 km且云顶高度可达7 km以上,作业云系的云夹层厚度对降水云催化效果影响较小。

In order to distinguish the cloud vertical structure(CVS) under different synoptic systems and provide reference for artificial rainfall enhancement, the characteristics of 500-850 hPa surface circulation field during Liaoning artificial rainfall enhancement periods from 2004 to 2014 and the CVS observed by CloudSat under typical synoptic systems(occurrence frequency larger than twice per year) are analyzed.According to the configuration difference of circulation filed, about 225 episodes, namely 17 types of synoptic systems, are identified, of which 4 typical types are selected, including westerly trough-shear linecold front(CF), westerly trough-vertex-Mongolia cyclone(MCW), westerly trough-vertex-southern cyclone(SC) and vertex-vertex-Mongolia cyclone(MCV). The analysis of CVS under typical systems shows that the dominated clouds are single-layer clouds. Under the influence of SC,the heights of cloud bases are lower and cloud thicknesses are thicker than that of other systems while that of MCW are opposite. More than 50 % of cloud intervals’ thicknesses are smaller than 1 km, and this proportion increases with the layer numbers. Taking the clouds with base height≤2 km and thickness≥2 km as the target clouds for artificial rainfall enhancement, we achieve the results that the proportion of qualified clouds under cloudy condition of SC is the highest(59. 7%) and that of MCW is the lowest(14. 5%). The target clouds are dominated by single-layer-low-cold clouds with base heights lower than 1 km and top heights higher than 7 km.Moreover, the thicknesses of cloud intervals have little effect on cold clouds seeding.