2011年7月31日黑龙江省暴雨天气诊断分析

应用常规观测资料、NCEP再分析资料和卫星云图产品,对2011年7月31日黑龙江省西部暴雨天气成因进行诊断分析。讨论了产生暴雨的天气系统特征,大气不稳定条件及产生暴雨的水汽条件和动力触发机制。结果表明：暴雨是由低涡、低涡槽前暖湿气流与冷空气的共同影响产生的。低层强盛的偏南气流建立起水汽通道,将水汽源源不断地向暴雨区输送。低层增温增湿使得大气层结不稳定。低层较强的西北气流与强盛的东南暖湿气流汇合,产生强切变,辐合上升运动增强,为暴雨的产生提供了动力条件,有利于不稳定能量释放。高层辐散与低层辐合相配合,有利于上升运动发展和维持。地面中尺度低压和中尺度辐合线为中尺度云团的发展和维持提供了条件;中尺度云团在暴雨区旋转停留近21 h,这是暴雨发生的主要原因。

Diagnostic analysis of a heavy rain process on July 31, 2011 over Heilongjiang province

Based on the conventionally observational data,the NCEP reanalysis data and satellite cloud image,the formation reasons of heavy rain weather on July 31,2011 in the west of Heilongjiang province were diagnosed.The weather system characteristics,atmospheric instable conditions,water vapor condition causing this process and dynamically triggering mechanism were discussed.The results indicate that the heavy rain is caused by the interaction of low vortex,warm-wet airflow in front of low vortex trough and cold air.The strong southerly airflow sets up a water vapor channel where water vapor can be transported to rainfall areas.The increase of temperature and humidity in the low level makes atmospheric stratification unstable.The strong northwest airflow converges with the strong southeast warm-wet airflow on low level and generates the strong wind shear,so convergence and ascending motion augment,which provide the dynamic condition for the heavy rain.At the same time,it is favorable to release the unstable energy.Upper divergence and lower convergence go together,which is favorable to the development and maintenance of ascending movement.Mesoscale low pressure and mesoscale convergence line on the ground provide the conditions for the development and maintenance of mesoscale cloud mass.The mesoscale cloud mass still stays about 21 hours in the areas of the heavy rain areas,which is the main reason causing the heavy rain.