我国冻雨时空分布及温湿结构特征分析

Analyses on Spatial-Temporal Distributions and Temperature-Moisture Structure of Freezing Rain in China

利用2008年1月-2010年4月全国常规地面观测资料和探空资料,根据地面观测冻雨记录,分析了我国冻雨的时空分布规律,并依据冻雨发生时探空分析的云顶同暖层(>0℃)相对位置等结构配置,初步研究了冻雨温湿结构特征和形成的物理机制类型。结果表明,我国冻雨一般从11月开始,到来年3月结束,以1月居多(占72%);冻雨多发生在长江以南区域,占总数的90%以上;我国冻雨发生主要以暖雨机制为主,占总数的73%,而冰相机制冻雨仅有27%;以暖雨机制产生的冻雨,云顶普遍不高(低于3km),而冰相机制冻雨云顶相对较高(可达9km);出现冻雨时,地面温度(百叶箱温度)均低于0℃,冰相机制冻雨的暖层厚度基本在1km以上,暖层最高温度平均在3℃以上;我国北方(30°N以北的地区)发生冻雨的机制比较单一,主要是冰相机制,南方(30°N以南的地区)冻雨两种机制都存在,受地形影响,一般在海拔高的地区暖雨机制比冰相机制多。

The spatial and temporal distributions of the freezing rain in China is analyed using the surface observation data from January 2008 to April 2010.And then,the vertical structures of cloud and atmospheric temperature from sounding,for example,the relative locations of cloud top height and warm layers（T〉0 ℃）,are used to study the temperature and moisture structures and the type of formation mechanism of freezing rain.The results show that the freezing rain occurs mostly from November to March,with the highest concentration in January（accounting for 72% of the total number）.Over 90% of all freezing rain occur the areas to the south of Yangtze River,leaving only a few to other regions.According to different formation mechanisms,freezing rain can be divided to two patterns： Warm rain mechanism（WRM） and ice-phase mechanism（I-PM）.The WRM account for 72%,while I-PM only 27%,among of all freezing rain detected here.The cloud top heights of WRM are low（below 3 km）,while those for I-PM are relatively higher（reaching 9 km）;The temperature of ground（instrument shelter） is lower than 0 ℃;The thickness of I-PM warm layers is basically more than 1 km and their maximum temperatures are higher than 3 ℃.It is likely that formation mechanism of freezing rain is regionally variable,with I-PM almost solemnly dominates in regions to the north of 30°N,and two mechanisms both exist in regions to the south of 30°N.Affecting by topography,WRM occurs more often than the other in high-altitude areas.