海南东方热带气旋的极端降水特征及个例分析

Characteristics of Extreme Precipitation of Tropical Cyclone Affecting Dongfang City and Case Analysis

利用2009—2020年海南省东方市的加密自动站资料、ERA5再分析数据以及CLDAS大气驱动场降水数据,将西行或西北行且影响东方市的热带气旋(TC)分为4类,并将其进行了极端降水特征分析,同时还通过典型TC个例分析了极端的降水的成因.结果发现,在I路TC过程,极端降水自西向东递增;在Ⅱ路TC过程,极端降水分布表现为北部小、南部大;在Ⅲ路TC过程,极端降水呈现自南向北递减趋势;在Ⅳ路TC过程,极端降水自西向东递减;在4类典型TC个例的强降水过程中东方市从低层到高层均伴有强盛的垂直上升速度(不小于-3 Pa·s^(-1));低层具有强烈的水汽通量辐合,不小于-25×10^(-5)g·cm^(-2)·s^(-1);均具有低层辐合高层辐散的动力配置,低层辐合强度不小于-20×10^(-5)s^(-1),高层辐散不小于25×10^(-5)s^(-1);非地转湿Q矢量散度可以较好地表征未来0~1小时强降水落区和移动趋势,强降水落区出现于湿Q矢量散度辐合区或湿Q矢量散度辐合区与辐散区的交界处.

In the report,the 2009-2020 Dongfang City encrypted automatic station data,ERA5 reanalysis data,and CLDAS atmospheric driving data,were used,the westbound or northwest tropical cyclone(TC)affecting Dongfang City were divided into four types,and the extreme precipitation were analyzed,and the typical cases were used for analyzing the causes of extreme precipitation. The results suggested that the extreme precipitation distribution of the landfall type TC from the Pearl River Delta to the Leizhou Peninsula(referred to as Route I)increases from west to east. The extreme precipitation distribution of landfall type TC,from Haikou to Wenchang(referred to as Route II),is smaller in the north than that in the south. The extreme precipitation of landfall type TC from Qionghai to Lingshui(referred to as Route Ⅲ)showed a decreasing trend from south to north.The extreme precipitation distribution of the type TC passing by Sanya or passing offshore(referred to as Road IV)decreases from west to east. The four TC processes in Dongfang City are all accompanied by a strong vertical rising velocity,reaching more than 3 Pa·s^(-1),the lower layer has a strong convergence of water vapor flux,reaching more than -25×10^(-5)g·cm^(-2)·s^(-1),the low layer convergence intensity reaches more than -20×10^(-5)·s^(-1),the up-layer divergence intensity reaches more than 25×10^(-5)·s^(-1). The non-geostrophic wet Q-vector divergence can characterize the rainfall area and moving trend of heavy precipitation in the next 0-1 hour very well. The heavy precipitation area appears in the wet Q-vector divergence convergent zone or the junction of the wet Q-vector divergence convergence zone and divergence zone.