2008年初持续雨雪灾害过程分析

利用地面实况资料与长沙单站探空等观测资料,对2008年1月中下旬至2月上旬初发生在湖南的低温、雨雪、冻雨灾害天气过程的影响实况和成因进行了分析.结果表明:中高纬阻高的建立、崩溃、重建导致其前部的鄂霍茨克海低涡不断引导冷空气南下,是产生低温、雨雪、冻雨的大气环流背景;南支锋区上强盛的西南气流带来了充沛的水汽,与北支锋区上南下的冷空气结合时,出现了持续的冻雨,当冻雨形成后逆温的强弱、融化层厚度及暖层温度高低、冷却层厚度、700 hPa西南气流强弱、日平均气温与日雨量的变化都与冻雨厚度变化密切相关;当高空南支有低槽分裂东移,中低层西南大风核上强烈的水汽辐合与阻高崩溃横槽转竖带来的冷空气共同作用影响时,为南方大范围暴雪过程提供了动力、水汽和凝结条件.

The analysis of persistent rain and snow, disasters process at the beginning of 2008

By using the conventional intensive observational data and sounding data of Changsha, the impact and the cause of formation of low temperature, rain, snow, sleet disasters process in Hunan from mid-January to mid-February 2008 were analyzed. Results show that the establishment, collapse and reconstruction of the blocking high in the high-latitude caused the cold air which was guided by the front of the vortex of the Ochotsk Sea to move southward continuously. It's the atmospheric circulation background which caused the cold temperature, rain, snow and freezing process. The persistent freezing occurs when the plentiful water vapor which was brought from the strong southwest stream on the Southern Branch front zone was combined with the southward cold air which came from the Northern Branch front zone. When freezing formed, the changes of the stream thickness had closely related to the temperature inversion intensity, the thickness of melted layer, the temperature of warming layer, the thickness of cooling layer, the intensity of 700 hPa southwest airflow, the daily average temperature and daily rainfall. When the low groove of South Branch split eastward, the strong moisture convergence in the lower southwest gale core was combined with the cold air which was brought by blocking high collapse and horizontal groove translated into vertical rotation to provide the dynamic, water vapor and condensatin conditions for the large range blizzard in the south.