1211号“海葵”台风登陆后引发两段大暴雨过程的对比分析

利用地面加密自动站观测资料以及NCEP再分析资料,对1211号“海葵”台风登陆后在江苏引发的两段降水对流特征差异明显的大暴雨天气进行对比分析。结果表明:第一段区域性大暴雨天气发生在台风环流中心及北侧偏东风急流附近,此时台风环流完整,中心维持正压结构,环流中心及其北侧偏东急流附近伴有较大范围的水汽辐合和强上升运动,有利于区域性大暴雨天气发生,但降水发生在近乎中性的层结下,降水分布较均匀,发展平缓,降水期间对流活动较弱;第二段大暴雨则发生在远离环流中心的台风倒槽顶部,降水期间暴雨区中高层伴有较明显的冷平流,有利于对流不稳定层结发展,降水发展过程中,地面风场出现中尺度扰动,增强了局地辐合和气旋性涡度,加之地面锋区发展,促进了中尺度对流系统的形成和发展,此段降水中尺度特征显著,发展迅速,雨强大,伴有明显的对流特征,导致出现局地特大暴雨天气。

Comparative analysis on two rainstorm processes caused by typhoon Haikui(1211) after landfall

By using the comprehensive information of automatic weather observation and NCEP reanalysis data,this paper contrasts and analyses two rainstorm processes caused by the landing typhoon Haikui(1211),which happened in Jiangsu with different convective features.It shows that the first-phase regional heavy rainstorm occurred near the typhoon circulation center and its north side.The circulation of typhoon was intact with a barotropic center during this time.Large-scale moisture convergence and strong ascending movement appeared near the circulation center and its north side in the easterly jet stream.These characteristics were beneficial for a regional rainstorm.The rainstorm occurred in a nearly neutral stratification,and precipitation distribution was more uniform with a gentler development,lower rainfall intensity and weaker convective activity.The second-phase heavy rainstorm occurred near the top of typhoon inverted trough,which was far from the circulation center.The cold thermal advection in the middle and upper atmosphere was helpful for the development of convective instability.During the process of precipitation development,obvious mesoscale disturbances appeared in the surface wind field,enhancing the local convergence and cyclonic vorticity.Furthermore,the development of surface frontal zone also strengthened the formation and development of mesoscale convective systems.The precipitation had significant mesoscale characteristics with rapid development,high rainfall intensity,strong convection,which led to a local heavy rainstorm.