一次东北冷涡暴雨数值模拟及动力诊断分析

利用常规观测资料、NCEP再分析资料和卫星云图产品，对2009年6月18-19日黑龙江省西南部地区的一次东北冷涡暴雨过程进行诊断分析，并利用WRF中尺度模式对暴雨过程进行数值模拟，分析产生暴雨的天气尺度和中尺度特征。结果表明：此次暴雨是由东北冷涡前部的暖湿切变造成的，鄂霍次克海阻塞高压阻挡使冷涡移动缓慢，使冷涡系统影响时间长，降水量增大。暖湿空气在切变处强烈辐合上升，为暴雨产生提供了动力条件；低空偏南急流为暴雨提供充沛的水汽条件，同时低层增温增湿使大气层结不稳定。低层强辐合区与高层强辐散区重叠，易产生强烈的上升运动，有利于深对流的发展和中尺度系统的生成及维持。暴雨是由暖锋云带中多个对流云团的发展移动造成的，地面中尺度切变线为暴雨云团的发展和维持提供了有利条件。数值模拟结果显示此次暴雨是由两次中尺度切变线先后在同一区域的发展和移动造成的；切变线上存在与暴雨关系密切的中尺度垂直环流。

Numerical simulation on a rainstorm process caused by Northeast China cold vortex and its diagnostic analysis

Based on conventionally observational data,the NCEP reanalysis data and satellite cloud image,a rain-storm process caused by Northeast China cold vortex in the southwest of Heilongjiang province on June 18-19, 2009 was analyzed and simulated by a WRF numerical model.The effects of weather system and mesoscale charac-teristics were discussed.The results indicate that the heavy rain is caused by warm-wet shear in front of Northeast China cold vortex.Cold vortex moves slowly because of impeding effect of Okhotsk high,which leads to increase of precipitation.The strong convergence and updraft of strong southeast warm-wet airflow on the shear provide dy-namic conditions for the heavy rain,while low-level jets supply abundant water vapor for the heavy rain.The in-crease of temperature and humidity in the low level makes atmospheric stratification unstable.Low strong conver-gence area and upper strong divergence area overlay,which consequently leads intense ascending movement.It provides conditions of deep convection development and promotes the formation and maintenance of mesoscale system when heavy rain occurs.Rainstorm is caused by development and movement of several mesoscale cloud clusters that is in the cloud belt of warm front.The mesoscale convergence line on the ground provides the advanta-geous conditions for the development and maintenance of mesoscale cloud clusters.The numerical simulation result suggests that rainstorm happens because two mesoscale shear lines develop and move successively in the same re-gion.There is a mesoscale vertical circulation which is related to rainstorm on the mesoscale shear line.