台风“苏迪罗”螺旋雨带造成福州特大暴雨成因分析

THE ANALYSIS OF AN UNUSUALLY HEAVY RAIN INDUCED BY THE OUTER RAINBAND OF TYPHOON SOUDELOR IN FUZHOU

受2015年第13号台风"苏迪罗"影响,福州出现特大暴雨。为研究台风登陆前局地强降水与地形的关系,针对福建长乐雷达的0°仰角数据进行了风场反演,得到福州低空风场在强降雨发生时的结构及演变特征,综合利用NCEP 1°×1°再分析资料及福州三维地形数据,探索了福州地区持续性短时强降水的发生原因。结果表明:(1)"苏迪罗"影响期间正值南海季风爆发期,为台风提供了充沛的水汽;(2)强降雨发生时,福州地区存在正涡柱,配合强烈上升运动,为短时强降水的发生提供良好的动力条件;(3)雷达风场反演显示:当福州环境风场为东北气流,有一持久、稳定的分流区出现在福清北部,随着台风靠近,环境风逐渐由东北转为偏东风,分流区的位置也一直向内陆延伸,分流气流与台风环境气流形成了明显的辐合带,激发了螺旋雨带内中尺度对流云团的发生发展,造成短时强降水;(4)台风环境气流进入福州后出现的分流现象与福州的盆地地形有关。

In August 2015,subject to the impact of Typhoon'Soudelor',Fuzhou suffered an unusually heavy rain.To study the relationship between the heavy rainfall and the terrain,radar-based low-level wind retrieval was analyzed to determine the structure of low-level wind field and the features of its evolution.The NCEP reanalysis data and 3D Fuzhou terrain were used to explore the causes of short-term rainfall in Fuzhou.What the study reveals is shown as follows:(1)A South China Sea summer monsoon provided abundant water vapor for the heavy rainfall.(2)There existed positive vortex in Fuzhou during the heavy rain,which provided favorable condition,coupled with intensive vertical motion.(3)Radar-based low-level wind retrieval showed that there existed a stable air flow at the north of Fuqing area when the wind field was northeasterly.As the typhoon approached,the wind field switched from northeast to east.A convergence zone was generated by a stable extended inland air flow and the typhoon wind field,which stimulated the development of meso-scale convective clouds in a spiral rain band.(4)The wind field of the typhoon was associated with the terrain of Fuzhou.