一次重庆特大暴雨过程的中尺度分析

Analysis of Heavy Rain Caused by Shear Line over Chongqing

利用NCEP格点再分析资料、地面实况资料、TBB资料以及雷达资料对2011年7月6 7日重庆大暴雨过程进行了分析研究。结果表明,此次暴雨过程中切变线附近发展起来的中尺度对流系统是暴雨产生的直接原因,且从动力、热力、水汽条件以及能量等方面分析表明重庆东北部已具备暴雨发生的有利条件。通过雷达产品的分析可知,两个阶段降水的中尺度特征不同:第一阶段降水,径向速度场上出现逆风区,对应逆风区的回波较强,雨强较大,且垂直风廓线VWP显示高空有偏西偏南的强风速带下传,从而形成较深厚的西南气流风场;第二阶段降水,径向速度场上出现强度不对称的"牛眼"结构,存在风速辐合,同时VWP显示中低层有深厚的冷空气楔入,使暖湿空气抬升,降水在经过短暂的减弱后再次加强。

With NCEP reanalysis data,surface observed data,TBB data and radar data,the diagnosing analyses are made of a heavy rain in Chongqing from 6 to 7 July 2011. The result indicate that mesoscale convective system near shear line is the direct cause of heavy rain,and the analysis of dynamics,heat,w ater vapor condition and energy show s that the northeast of Chongqing has favorable conditions for heavy rain occurred. The analysis of radar product indicates that inverse wind area appears on Doppler velocity,under w hose influence,the echo and rainfall intensify. And VWP also show s that the w est and south strong w inds bring dow n to low-level to form a deep southw est airflow wind field. In second phase,the symmetrical intensity bull' s-eye structure appears on the Doppler velocity,w hich indicate that wind speed convergence existing in the precipitation area. At the same time,VWP show s that the low level strong northeast dry air intruding lifts w arm moist air and benefits to the occurrence development of convective motion,w hich is favorable to strengthen the heavy rain again after brief w eakened.