“苏拉”台风引发福建西部大暴雨成因分析

Causal Analysis of Heavy Rainfall over Western Fujian Province Caused by Typhoon Saola

利用常规天气资料、NCEP 1°×1°再分析资料、地面降水资料以及福建新一代天气雷达资料对2012年"苏拉"台风登陆后引发福建西部大暴雨天气成因进行分析,结果表明:"苏拉"登陆后高空涡旋受大陆高压东侧偏北气流引导向偏南方向移动,同时,台风登陆后进入大的环境风垂直切变区并向切变左侧倾斜,使得台风南倾结构进一步加大。台风结构南倾为福建西部大暴雨区提供了良好的动力条件,"苏拉"自身带来的水汽及台风南侧西南气流为暴雨区提供了充足的水汽来源,高空冷空气入侵与低层的高温高湿区形成上冷下暖结构呈现出条件不稳定层结,有利于深厚湿对流产生,结合充分的水汽供应,出现大暴雨天气。大范围暖平流配合风速辐合,中高层冷空气入侵与低层西南暖湿空气结合以及低层的西南急流建立是三个强降水阶段对应的中尺度天气特征。

Utilizing the conventional meteorological data, NECP 1°×1° reanalysis data, surface precipitation and Fujian CINRAD/SA data, the cause of the heavy rainfall over the western Fujian Province after Saola Typhoon landing is analyzed. The results show that the northerly flow of Continental High Pressure led to the southward movement of Saola＇ s upper vortex. When the typhoon entered the large environmental vertical wind shear zone, the typhoon tilted to the left of the shearline, which made typhoon move more southward. The south tilting structure provided favorable dynamic condition over heavy rainfall region. The water vapor transportation supplied by Typhoon Saola and the typhoon＇s southwest airflow provided sufficient moisture for the heavy rainfall. The cold air intrusion at upper levels and warm and moist air at low levels induced the conditional instability, which was favorable for the development of deep wet convection. Warm advection combined with velocity convergence, the incursion of dry cold air at upper level, warm and moist air at low levels, and the establishment of the southwest jet at lower levels were three meso-scale systems favorable for the severe rain.