一次台风后部中尺度暴雨的动力机制分析与模拟试验

Dynamic Mechanisms and Numerical Experiment of a Mesoscale Rainstorm in Rear of a Typhoon

利用常规气象资料、区域自动站资料和1°×1°的NCEP再分析资料,对1209"苏拉"台风后部暴雨的动力机制进行分析,并用WRF模式进行地形模拟数值试验,结果表明:"苏拉"后部暴雨具有明显的中尺度特征,低层流场的汇合促进暴雨区上升运动的发展,超低空偏南风急流为暴雨区提供充足的水汽条件,急流在强降水发生前增强北推;陆地摩擦使近岸一带生成风速辐合线(岸风锋)是触发暴雨的中尺度系统,其强弱对暴雨强度有直接影响。

Based on the conventional station,regional automatic station,and NCEP 1°× 1°reanalysis data,the dynamic mechanisms of a heavy rainstorm in the rear of the typhoon Sura are analyzed,and terrain simulation is conducted by WRF model.The results show that the heavy rain presented obviously mesoscale features;the convergence of the low level flow field promoted the development of the ascending movement in the heavy rain area;the very-low-altitude southerly jet provided sufficient vapor conditions;the jet stream strengthened and moved northward before the heavy rain occurred.Because of the convergence line of wind speed induced by the land friction effect along the coastal area,the mesoscale heavy rain system was triggered,the strength of which had a direct impact on the heavy rain intensity.