Influence of Irregular Coastlines on a Tornadic Mesovortex in the Pearl River Delta during the Monsoon Season. Part Ⅰ:Pre-storm Environment and Storm Evolution  

作　　者：Lanqiang BAI Dan YAO Zhiyong MENG Yu ZHANG Xianxiang HUANG Zhaoming LI Xiaoding YU 

机构地区：[1]Foshan Tornado Research Center,and China Meteorological Administration Tornado Key Laboratory,Guangdong Meteorological Service,and Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Guangdong 528000,China [2]Meteorological Observation Centre,CMA,Beijing 100081,China [3]Department of Atmospheric and Oceanic Sciences,and China Meteorological Administration Tornado Key Laboratory,School of Physics,Peking University,Beijing 100871,China [4]Guangzhou Meteorological Observatory,CMA,Guangdong 511430,China [5]Foshan Tornado Research Center,and China Meteorological Administration Tornado Key Laboratory,CMA,Guangdong 528000,China [6]China Meteorological Administration Training Center,CMA,Beijing 528000,China

出　　处：《Advances in Atmospheric Sciences》2024年第6期1115-1131,共17页大气科学进展（英文版）

基　　金：supported by the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030004);the National Natural Science Foundation of China(Grant Nos.42275006 and 42030604);the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011705);the Science and Technology Research Project for Society of Foshan(Grant No.2120001008761).

摘　　要：The Pearl River Delta(PRD),a tornado hotspot,forms a distinct trumpet-shaped coastline that concaves toward the South China Sea.During the summer monsoon season,low-level southwesterlies over the PRD’s sea surface tend to be turned toward the west coast,constituting a convergent wind field along with the landward-side southwesterlies,which influences regional convective weather.This two-part study explores the roles of this unique land–sea contrast of the trumpet-shaped coastline in the formation of a tornadic mesovortex within monsoonal flows in this region.Part I primarily presents observational analyses of pre-storm environments and storm evolutions.The rotating storm developed in a lowshear environment(not ideal for a supercell)under the interactions of three air masses under the influence of the land–sea contrast,monsoon,and storm cold outflows.This intersection zone(or“triple point”)is typically characterized by local enhancements of ambient vertical vorticity and convergence.Based on a rapid-scan X-band phased-array radar,finger-like echoes were recognized shortly after the gust front intruded on the triple point.Developed over the triple point,they rapidly wrapped up with a well-defined low-level mesovortex.It is thus presumed that the triple point may have played roles in the mesovortex genesis,which will be demonstrated in Part II with multiple sensitivity numerical simulations.The findings also suggest that when storms pass over the boundary intersection zone in the PRD,the expected possibility of a rotating storm occurring is relatively high,even in a low-shear environment.Improved knowledge of such environments provides additional guidance to assess the regional tornado risk.

关 键 词：TORNADO mesovortex surface boundary land–sea contrast MONSOON 

分 类 号：P445[天文地球—大气科学及气象学]