基于精细化观测的揭阳市台风降水分布及环流特征分析

Analysis of Typhoon Precipitation Distribution and Circulation Characteristics in Jieyang City Based on Refined Observations

基于2013—2022年登陆广东的热带气旋(统称为台风,下同;包括1个登陆香港地区)及台风影响期间揭阳市85个气象观测站的降水观测资料和欧洲中期天气预报中心(ECMWF)ERA5的0.25°×0.25°环流数据,应用统计分析、合成分析等方法,分析台风造成的揭阳市降水的时空精细化分布特征和环流特征。结果表明:2013—2022年登陆广东的台风造成揭阳市平均面雨量(揭阳市85个气象观测站录得雨量的平均值,下同)为245.6 mm/a,2018年为10年间最多,平均面雨量达455.2 mm;降水月际变化呈单峰型分布,主峰出现在8月,平均面雨量为100.5 mm。不同登陆路径造成的揭阳市降水分布特征不同:台风东路登陆时揭阳市平均面雨量最大,其次是西路登陆,中路登陆时平均面雨量最小,平均面雨量分别为90.3 mm、76.2 mm、58.3 mm;台风西路登陆时1 h最大降雨量最大,其次是东路,中路登陆时1 h最大降雨量最小,分别为92.2 mm、89.6 mm、64.7 mm。台风不同路径登陆时,揭阳市强降水中心(面雨量超过100 mm的区域,下同)的位置不同,随着登陆路径的西移依次往西移,东路登陆时最强降水中心出现在普宁东南部下架山汤坑水库到惠来东北部河林乡一带,中路登陆时最强降水中心出现在揭西五经富、五云、普宁鲘溪乡等地区,西路登陆时出现在普宁军埠、揭西河婆等地区,3个最强降水中心都处在山脉的迎风坡。不同登陆路径的台风环流形势特征不同:台风东路登陆时,揭阳市处于台风中心附近环流场中,降水重点是台风本体降水;台风中路登陆时,以台风外围环流及副热带高压西南侧不稳定降水为主;台风西路登陆时,揭阳市附近处于偏南气流转东南气流的气旋性弯曲处,有利于水汽的辐合。在三种路径登陆的台风影响下,揭阳市降水量东路的>西路的>中路的,台风西路和中路登陆时,揭阳市受其外围环流影响,降水量的大小与台风登陆点远近没有很好对应关系,主要取决于环流形势。

Based on the tropical cyclones that landed in Guangdong from 2013 to 2022(collectively referred to as typhoons,the same below;including one landing in Hong Kong region),precipitation observation data from 85 meteorological observation stations in Jieyang City during the typhoons’impact periods,the European Centre for Medium Range Weather Forecasts(ECMWF)ERA50.25°×0.25°circulation data,as well as the statistical analysis and cluster analysis methods,this paper analyzes the spatial distribution characteristics and circulation characteristics of the typhoon-caused rainfall in Jieyang City.The results show that typhoons that landed in Guangdong from 2013 to 2022 caused an average areal rainfall of 245.6 mm per year in Jieyang City,with a maximum of 455.2 mm in 2018 over the 10-year period.The monthly variation of precipitation shows a unimodal distribution,with the main rainfall peak seen in August and the average areal rainfall of 100.5 mm.Different landing paths resulted in different distribution characteristics of rainfall in Jieyang City.The typhoons that landed in the east path had the maximum average areal rainfall,followed by the average areal rainfall of typhoon landing in the west path,and the average areal rainfall was the lowest when typhoons landed in the middle path.The corresponding average areal rainfall amounts in the three paths were 90.3 mm,76.2 mm and 58.3 mm,respectively.When typhoon landed in the west path the hourly rainfall(92.2 mm)was the most,the second most hourly rainfall(89.6 mm)was with the landfall typhoon in the east path,and the least hourly rainfall(64.7 mm)was found in case typhoons landed in the middle path.Typhoons that landed on different paths had different locations of heavy precipitation centers(areal rainfall>100 mm)in Jieyang City.As the typhoon landing path moved westward,the heaviest precipitation centers on the east path appeared in the area from Tangkeng Reservoir of Xiajiashan Town in the southeast of Puning City to Helin Town in the northeast of Huilai County;the heaviest precipitation centers in the middle path appeared in areas of Wujingfu Town and Wuyun Town of Jiexi County and Houxi Town of Puning City;and the heaviest precipitation centers in the west path appeared in areas of Junbu Town of Puning City and Hepo Town of Jiexi County.All of these heaviest rainfall centers were located on the windward slopes of mountain ranges.The circulation characteristics of typhoons with different landfall paths were different.For typhoons that landed in the east path,Jieyang City was located in the circulation field near the center of the typhoon,and the precipitation was mainly from the typhoon itself;the typhoons that landed in the middle path were mainly characterized by the rainfall from the peripheral circulation of the typhoon and unstable precipitation on the southwest side of the subtropical high;the typhoons that landed in the west path were located near Jieyang City at a cyclonic bend where the southerly airflow turned into the southeasterly airflow,which was more conducive to the convergence of water vapor.Overall,the precipitation of the east path typhoons>that of the west path typhoons>that of the middle path typhoons in Jieyang City.With typhoons of the west path and the middle path,Jieyang City was affected by their peripheral circulations.The amount of precipitation did not correspond well with the distance of the typhoon landing point,mainly depending on the circulation situation.