宁夏一次大到暴雨过程成因分析

利用地面、高空常规观测资料、数值预报物理量场以及卫星、雷达、自动站等资料，综合分析了2009年8月18日发生在宁夏的全区性大到暴雨过程．分析表明，台风“环高”的生成发展与西太平洋副高（简称副高）之间的相互作用，形成了有利宁夏降水的“东高西低”的环流形势，在副高东退过程中宁夏出现明显降水．500hPa短波槽和700hPa低涡是造成降水的天气系统．降水期间，中低层有明显的水汽和不稳定能量输送，且存在层结不稳定条件；云图中有多个中小尺度对流云团先后影响；雷达回波图上，此次降水过程表现为混合性降水，强降水由多个强度35～40dBz的强回波块影响造成，出现强降水的站点附近有“逆风区”或明显的气流辐合区存在，有明显的中小尺度上升运动，在雷达反演的风廓线可分析出“低层暖平流，高层冷平流”的配置．

Analysis on Causes of A Heavy Rain Process Occurred over Ningxia

By using conventional observation data,numerical prediction model products,satellite,radar and automatic meteorological station data,a heavy rain process occurred over Ningxia on August 18 in 2009 is analyzed.The results show that the beneficial precipitation circulation for Ningxia which is high pressure ridge at east and low pressure trough at west is founded because of the interaction of west pacific subtropical high and typhoon VAMCO,during the moving back stage of west pacific subtropical high,heavy rain occurred in Ningxia.The weather systems which caused heavy rain are short-wave trough at 500 hPa and low vortex at 700 hPa.From satellite picture we can see that there are several meso and micro-scale convective cloud cell which caused heavy rain.In middle and low level,there are remarkable transportation of water vapor and instable energy,and stratification is instable.On radar images,the heavy rain process showed the characteristics of mixed precipitation process,several strong echoes of 35-40 dBz caused heavy rain,and there is adverse wind area or obvious convergence area around the stations with heavy rainfall,so there is obvious meso and micro scale ascending motion during heavy precipitation stage,from radar wind profile we can see that there was warm advection at low level and cold advection at high level.