一次盛夏罕见连阴雨过程分析

目的]分析2009年7月22日～8月14日安徽省出现的一次罕见低温阴雨过程。方法]利用常规观测、NCEP分析场及自动站等资料对2009年7月22日～8月14日安徽省出现的一次罕见低温阴雨过程进行分析,探讨这次盛夏连阴雨过程的成因,揭示导致连阴雨的环流特征和影响系统,并在此基础上,分析了高低层环流场的配置及物理量场的差异对降水范围、强度的影响。结果]这次连阴雨过程根据环流形势和影响系统可以分为7月22～24日、7月27日～8月1日、8月4～8日、8月9～14日4个阶段,且4个阶段分别受东北低涡影响、冷暖空气共同影响、高空低槽影响以及台风和副高外围影响;过程中大比湿区的维持为连阴雨提供了充足的水汽条件;暴雨出现在等比湿线密集区内,即湿度锋区比湿中比湿〉13 g/kg的区域;850 hPa上空维持一温度槽,不断扩散南下的冷空气既是造成连阴雨期间异常低温的主要原因,同时也为降水维持提供了上升运动条件。结论]该研究为实际预报和服务工作提供参考依据。

Analysis of a Rare Continuous Rainy Process in Midsummer

Objective] The research aimed to analyze a rare low temperature and rainy weather process which happened in Anhui Province from July 22 to August 14,2009.Method] Based on the data of conventional observation,NCEP analysis field and automatic station,a rare low temperature and rainy weather process which occurred in Anhui province from July 22 to August 14,2009 was analyzed.The formation reason of continuous rainy process in midsummer was discussed.The circulation characteristics and influence system of continuous rainy process were revealed.On the base,the influences of configuration of circulation field at high and low layers and difference of physical quantity filed on range and strength of precipitation were analyzed.Result] According to the circulation situation and influence system,the continuous rainy process could be divided into four stages: July 22-24,from July 27 to August 1,August 4-8 and August 9-14.Moreover,it was respectively affected by northeast low vortex,cold and warm air,high-latitude low trough,typhoon and periphery of subtropical high in four stages.The maintenance of big specific humidity zone provided sufficient water vapor condition for the continuous rainy weather.The rainstorm appeared in dense zone of specific humidity line,where the specific humidity >13 g/kg in the frontal zone of humidity.One temperature trough maintained at 850 hPa.The cold air which continued to diffuse and go south was main reason of the abnormal low temperature during continuous rainy period.Moreover,it provided ascending motion condition for precipitation maintenance.Conclusion] The research provided reference basis for actual forecast and service work.