台风“苏迪罗”螺旋雨带造成福州特大暴雨成因分析

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。 

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

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.