台风“威马逊”(1409)在南海北部急剧增强的环境因子分析

Analysis on environmental factors of the extremely rapid intensification of typhoon“Rammasun”(1409)in the northern South China Sea

利用ECMWF-interim逐6 h再分析资料、中国气象局台风最佳路径资料和NOAA逐日OISST海表温度等资料,并采用ARW-WRF中尺度数值模式,对1409号台风“威马逊”在南海北部海域急剧增强的原因进行分析和数值敏感性试验。结果表明:低层西南季风气流突然增强和高空东风急流异常偏强的高低空环流的最佳配置,是此次台风在南海北部海域急剧增强的主要动力机制;整层环境风垂直切变较大,而低层环境风垂直切变小,高层出流强、低层水汽充沛,是台风在南海北部海域快速增强过程中所独具的环境特征;南海北部海温异常偏高是造成此次台风猛烈发展并出现登陆极端强度的决定性因子。

Based on the ERA-Interim reanalysis data,CMA typhoon best track data,and the NOAA 1/4°daily OISST data,the reasons of the rapid intensification of the typhoon“Rammasun”(1409)in the northern South China Sea is analyzed and numerical sensitive experiments are conducted by using WRF.The results show that the sudden enhancement of the low-level monsoon flow and the abnormally strong upper easterly jet is the main dynamic mechanism of the rapid intensification of typhoon“Rammasun”in the northern South China Sea.The typhoon rapid intensification in the northern South China Sea is featured by large vertical shear of the environmental wind from the top to the bottom,small vertical shear in the low-level wind,strong high-level outflow and abundant low-level water vapor.Moreover,the abnormally high SST in the northern South China Sea is a crucial factor for the rapid intensification and extreme landing intensity of typhoon“Rammasun”.