台风“苏拉”登陆福建后降水的非对称成因分析

Analysis of the precipitation asymmetries of typhoon Saola after its landfall on Fujian Province

摘要:

利用常规天气资料、NCEP再分析资料、卫星云图、新一代天气雷达等资料，分析了2012年第9号台风"苏拉"降水预报失败的原因及其暴雨成因。结果表明：此次台风暴雨预报失败的主要原因在于预报过程中没有关注台风垂直结构的改变及其对降水落区的影响。"苏拉"台风暴雨是在中高纬稳定的环流形势下发生的，低层到高层引导气流的变化导致"苏拉"高层风暴中心向南倾斜；环境风垂直切变导致了台风降水的非对称分布，环境风垂直切变方向的左侧是强降水发展的区域；此外，随着台风环流中心在垂直方向发生偏移，改变了涡度平流的垂直分布，从而导致了福建省南部的暴雨。因此关注登陆台风中心在垂直方向的偏移对台风降水预报非常重要。

关键词:台风“苏拉”;非对称分布;台风降水;引导气流;环境风垂直切变

Abstract:

By using the conventional meteorological data,NCEP 1°×1° reanalysis data,Satellite Images data and CINRAD/SA data,the reason for the failure of the foecast and the cause of the heavy rainfall after Saola Typhoon landing is analyzed.Asymmetric distribution of precipitation by Typhoon Saola has been analyzed from circulation background,change of vertical structure,steering flows,environmental vertical windshear,physical quantity diagnosis and so on.The results show that:The main reason for the large deviation of typhoon rainstorm forecast and actual situation is that little attention has been paid to the change of the vertical structure of typhoon and its impact on the precipitation area during the forecasting process.The stable circulation background of high latitude provides favorable conditions of asymmetric distribution of typhoon precipitation;the change of steering flows in the vertical tilted the typhoon center southward with height;the steering flows and environmental vertical wind shear are the reasons which caused the typhoon center southward with height;The change of the vertical wind shear indicates the heavy rainfall region,which reflects the stronger convection and rain on the left of downshear;In addition,while the typhoon center southward with height,the distribution of the vorticity has to been changed,so the heavy rainfall happened in the southern Fujian proivince.Therefore,it is important to pay attention to the change of this vertical structure of typhoon.

Key words:typhoon Saola;asymmetric distribution;precipitation associated with typhoon;steering flows;environmental vertical wind shear