热带低压倒槽引发江苏东北部大暴雨过程分析

Analysis on heavy rainfall event triggered by inverted typhoon trough in the northeast region of Jiangsu province

利用常规观测资料、NCEP 1°×1°再分析资料、加密自动观测站资料、连云港风廓线雷达和多普勒天气雷达资料等,对2012年8月10日江苏东北部地区特大暴雨过程进行了分析。结果表明:台风"海葵"登陆后在安徽东南部减弱成热带低压,北伸的低压倒槽与高空低槽的结合,是产生这次特大暴雨的天气背景。特大暴雨发生在大气层结极不稳定区域,同时具有水汽强辐合,对流层低层强辐合、高层强辐散的环境场特征。散度场的垂直分布特征变化先于降水强度的变化;冷空气从低层开始入侵,并向中高层渗透,触发了不稳定能量的释放。地面中尺度辐合线的长时间维持,是这次特大暴雨产生的直接原因。平均径向速度产品揭示的风向风速辐合、气旋性环流、低空急流及暖平流等的环境场特征,为短临预报中判断强降水发生及维持提供了依据。

Based on data of convention observation, NCEP 1 °×1° reanalysis, ground-based observa- tion, wind-profile radar in Lianyungang and Doppler weather radar, heavy rainstorm process on August 10, 2012 was analyzed. The result indicated that after landing in the southeast Anhui, typhoon ＂Haikui＂ weak- ened into a tropical depression. The combination of inverted trough stretching towards the north and upper- level trough was found to be the background of the heavy rainstorm happened in the northeastern Jiangsu Its ambient field was characterized by extreme unstable atmospheric stratification, moisture convergence center, convergence trough, upper-level divergence center and powerful ascending motion. Cold air pene- trated into the meso-sphere and upper-level from the lower atmosphere, which triggered the release of insta- ble energy. The lasting of medium-scale convergence line was the main reason of this heavy rainfall event. Wind convergence , cyclonic circulation , mesocyclone signature ,low-level jet,warm advection and greater radial wind field were revealed in the medium-scale environmental field signature during the torrential rain. According to these facts, the nowcasting of occurrence and maintaining of heavy precipitation is available.