台风“卡努”影响下浙江东北部暴雨增强成因

Causes of Rainstorm Enhancement in Northeastern Zhejiang Related with Typhoon Khanun Landing in Guangdong Province

基于地面常规观测资料、地面加密观测资料以及NCEP GFS分析场、热带气旋最佳路径、FY-2E卫星TBB资料,利用天气诊断和数值模拟相结合的方法,探讨2017年10月14—16日台风"卡努"在登陆广东期间引发浙江东北部暴雨增强的成因。结果表明:暴雨期间,低层有东南急流和东北风形成的台风倒槽,随着冷空气向近地面层渗透,浙江沿海地区有锋生,利于低层倒槽顶部气旋性环流形成,导致暴雨增强,锋生区与暴雨区有较好的对应,且水平辐散项是锋生过程的主要贡献项。在降水开始形成阶段,大尺度环流有利于暴雨的形成,局地地形和低层辐合作用导致强降水的发生;在暴雨增强过程中,低层辐合和低层对流不稳定的增强,是降水增强的重要原因,其中低层辐合增强来自于气旋性环流的形成和发展,强降水区始终位于低压环流的东北侧,且随着低压环流的东北移,降水大值区也东北移。

Based on conventional observation data,intensive observation data at automatic weather stations,the optimal path of tropical cyclone from China Meteorological Administration,analysis fields from NCEP/GFS and black body temperature data from FY-2 E satellite,the causes of heavy rainfall enhancement in Northeastern Zhejiang Province from 14 to 16 October 2017 caused by typhoon Khanun landing in Guangdong Province were analyzed by using weather diagnosis and numerical simulation method.The results show that the southeast jet and northeast wind in lower level formed typhoon inverted trough during the rainstorm.With the penetration of cold air on the ground,the frontogenesis formed in the coastal areas of Zhejiang Province,which was conducive to the formation of cyclonic circulation on the top of low-level inverted trough,and further led to the enhancement of heavy rainfall.The frontogenesis area was corresponding well with heavy rainfall region,and the horizontal divergence term was main contribution of frontogenesis process.At the beginning of precipitation formation,the large-scale circulation was beneficial to the formation of rainstorm,and the local topography and low-level convergence led to the occurrence of strong rainfall,but the convective instability wasn’t obvious.During the enhancement of heavy rainfall,the enhancement of convergence and convective instability in low level played important role in enhancing of precipitation.The enhancement of convergence in low level came from the formation and development of cyclonic circulation.The strong precipitation area was always located in the northeast side of cyclonic circulation,and the heavy rainfall area moved to northeast with the movement of cyclonic circulation to northeast.