摘要
利用分钟降水资料、FY-4A气象卫星高分辨率资料、多普勒天气雷达资料和ERA5再分析资料对2021年“7·20”河南极端暴雨过程中尺度系统精细结构及热动力发展机制进行观测分析和诊断研究,结果表明:该过程发生在“两高对峙”的鞍型场弱背景下,其主导系统为500hPa弱低压系统和低层偏东风切变线;极端暴雨主要由水平尺度约300km呈近乎圆形结构中尺度对流复合体产生,其长时间维持与内部多个中尺度对流系统的合并及外围东南侧暖湿区新生单体的持续并入有关;郑州站小时强降水(201.9mm·h^(-1))由几乎静止的低质心β中尺度弓状回波产生,其分钟降水量持续在3~4.7mm;边界层风场的动力辐合触发强烈对流,使得强降水区上空θse锋区长时间处于中性层结,其高层辐散气流在西北太平洋副热带高压附近构成次级环流下沉支;中层500hPa低压区气旋式曲率附近正涡度平流和925hPa偏东气流持续暖平流输送、低层变形场锋生作用,以及来自华东近海边界层急流异常强盛的水汽输送是此次极端过程发展维持的热动力学成因。
The typical circulation configuration,fine structure of mesoscale system and thermodynamic development mechanism of affecting system associated with the extreme heavy rainfall of Henan from 19 July to 21 July in 2021 are analyzed with data which contain minutely automatic weather station observations,FY-4 A satellite high-resolution measurements,Doppler radar products and the fifth-generation European Center for Medium-Range Weather Forecasts(ECMWF)atmospheric reanalysis(ERA5).Results show that the extreme heavy rainfall occurs under a weaken saddle field which is between the subtropical high and the continental high.The dominant systems are the weak low-pressure system at 500 hPa and easterly shear line at low level.A long-term maintained mesoscale convective cloud plays great roles in the extreme heavy rainfall of Henan,which features a nearly circular structure with a horizontal scale of about 300 km.The long-term maintenance of this cloud is related to the merging of its inside multipleβ-mesoscale convective systems.Meanwhile,the confluence of three easterly flows in the east of warm zone in the southeast of the periphery keep triggering new convective cells which are constantly integrated into the mesoscale convective cloud.These two processes lead to the train effect,which is crucial to the extreme heavy rainfall in Henan.The rainfall intensity at Zhengzhou Station is 201.9 mm·h^(-1),and breaks the hourly rainfall record in inland regions.It is mainly caused by quasi-stationaryβ-mesoscale convective systems,which show bow echo in Doppler weather radar.The vertical structure of the convective system,which has the strong echo centroid below 5 km in Doppler weather radar,reflects the extremely efficient precipitation.During the extreme rainfall from 1600 BT to 1700 BT on 20 Jul 2021,the minutely continuous precipitation is stable at 3-4.7 mm,and the 5-minute rainfall maximum could reach 21 mm.The strong convection is triggered by the dynamic convergence of the boundary layer wind,leading to the pseudo equivalent temperature(θ_(se))front above the heavy rainfall area maintaining in a neutral stratification of nearly barotropic structure for a long time.Meanwhile,the low-level convergence collocates with the high-level divergence,which benefits an intense ascend through the tropopause.The high-level divergent flow forms a sinking branch of the secondary circulation near the Northwest Pacific subtropical high.The significant positive vorticity advection near the cyclonic circulation at 500 hPa,the continuous warm advection transport by easterly flow at 925 hPa,the frontogenesis of low-level deformation field and the abnormally strong jet water vapor transport from the coast of East China are the thermodynamic mechanisms of the development and maintenance of the extreme heavy rainfall in Henan.
作者
齐道日娜
何立富
王秀明
陈双
Chyi Dorina;He Lifu;Wang Xiuming;Chen Shuang(China Meteorological Administration Training Center,Beijing 100081;National Meteorological Center,Beijing 100081)
出处
《应用气象学报》
CSCD
北大核心
2022年第1期1-15,共15页
Journal of Applied Meteorological Science
基金
公益性行业(气象)科研专项(GYHY201506006),中国气象局短时临近预报教学科研团队项目。
关键词
鞍型场配置
极端强降水
低压区
次级环流
变形锋生
saddle field
extreme heavy rainfall
low pressure area
secondary circulation
deformation frontogenesis
作者简介
通信作者:何立富,邮箱:helifu@cma.gov.cn。
