两次北上台风引发冀北极端降水的对比分析

Comparative Analysis of Extreme Precipitation in Northern Hebei Province Caused by Two Northward Typhoon Cases

利用NCEP/NCAR再分析资料、自动气象观测站数据,分析发生在河北省承德市的“安比”(1810)台风暴雨和“海棠”(1710)台风暴雨过程,比对冷空气活动、作用形式及其对降水的影响。结果表明:(1)两次过程在中纬度西风槽冷空气影响下的降水差异明显,“海棠”暴雨雨强明显强于台风“安比”,但后者降水生命史更长;(2)“海棠”残余环流北上影响承德市时,西风槽冷空气主体沿西北气流入侵环流,而台风“安比”暴雨过程仅受西风槽分裂出的弱冷空气影响。由于冷空气影响形式不同,前者的正涡度带沿切变区分布,大值区位于残余环流东侧,而后者的正涡度沿西风槽和台风环流分布,大值区位于环流西北侧。两次过程低层冷空气入侵均先于高层,较强冷空气影响台风环流时,有利于降水强度增强;弱冷空气影响环流时,则有利于降水强度维持。

The rainstorm processes of Typhoon“Ampil”(1810)and Typhoon“Haitang”(1710)in Chengde,Hebei Province in terms of the activity process,the forms of action,and the impact on precipitation of cold air were comparatively analyzed based on conventional observation data,ground automatic station data and NCEP(1°×1°)6h interval FNL reanalysis data.The results of the analysis showed that(1)there were obvious differences in precipitation between the two typhoon processes under the influence of cold air in the mid-latitude westerly trough,the depression rainstorm of Typhoon“Haitang”significantly stronger than that of the Typhoon“Ampil”,but the latter had a longer duration of precipitation;that(2)when the residual circulation of Typhoon“Haitang”going northward affected Chengde,the main part of cold air in the mid-latitude westerly trough invaded the circulation along the northwest airflow,but the rainstorm processes of Typhoon“Ampil”were only affected by the weak cold air split from the westerly trough;as the results of the different forms of cold air intrusion,the former positive vorticity zone was distributed along the shear zone,the large value zone was located on the east side of the residual circulation,while the latter positive vorticity zone was distributed along the westerly trough and typhoon circulation,and the large value zone was located on the northwest side of the circulation.The research indicated that the intrusion of cold air in the lower layer preceded that of the upper layer in both processes,when the strong cold flow affected the circulation,it was conducive to the increase of the precipitation intensity;when the weak cold flow affected the circulation,it was conducive to the maintenance of the precipitation intensity.