宜昌市致洪中尺度极端降水成因分析  

Causes of a flood-causing mesoscale extreme precipitation in Yichang City

作　　者：成勤 王清龙 孟芳 李芳 彭福强 雷东洋 CHENG Qin;WANG Qinglong;MENG Fang;LI Fang;PENG Fuqiang;LEI Dongyang(Three Gorges National Climate Observatory,Yichang 44300,China;Yichang Weather Bureau of Hubei Province,Yichang 443000,China;College of Marine Science and Technology,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]三峡国家气候观象台,湖北宜昌443000 [2]湖北省宜昌市气象局,湖北宜昌443000 [3]中国地质大学海洋学院,湖北武汉430074

出　　处：《人民长江》2024年第7期88-97,共10页Yangtze River

基　　金：湖北省自然科学基金项目(2023AFD106);三峡局地气候监测项目(SK2023019);湖北省气象局科技发展基金项目(2023Y13)。

摘　　要：极端降水对河流防洪调控、水库蓄水泄洪等具有重要的影响,研究极端降水成因成为强化区域洪水资源管理的必要环节。基于多源观测资料和ERA5再分析资料,利用HYSPLIT后向轨迹模式和锋生强度诊断等方法,对2023年8月26日夜间宜昌市致洪中尺度极端降水成因进行分析。结果表明:①此次极端降水过程关键影响系统为低空急流、超低空急流、边界层冷空气和中尺度低涡。强降水可以分为中尺度低涡新生、低空急流发展,冷暖对峙、冷锋南下,低涡中心东移3个阶段。②此次过程中低层主要有4条暖湿输送通道,强降水区水汽通量超800 kg/(m·s),可降水量超70mm。③强降水时段低层相对涡度正值中心与垂直速度负值中心基本重合,加之锋生作用增强,强降水中心低层垂直速度达-7.1 Pa/s。④强降水时段,地形过渡带附近形成θ_(se)(假相当位温)能量锋区,垂直方向上出现高能舌,800 hPa附近中心强度达360 K以上。⑤中尺度地形形成了“西北冷干、东南暖湿”中尺度温湿锋区,并起到了阻挡抬升和触发作用,使强降水出现在山前喇叭口内。研究成果可为汛期区域洪水资源管理策略制定提供依据。Extreme precipitation has an important impact on flood control and water dispatch of rivers and reservoirs.Studying the causes of extreme precipitation is a necessary stage to strengthen regional water resources management.Based on multi-source observation data and ERA5 reanalysis data,using HYSPLIT backward trajectory model and frontogenesis intensity diagnosis,the causes of a flood-causing extreme heavy precipitation in Yichang City on the night of August 26,2023,were analyzed.The results indicated that:①In this extreme precipitation process,the low-level jet,super low-level jet,boundary layer cold air,and mesoscale vortex were the key influencing systems.The heavy rainfall period could be divided into three stages:the formation of the mesoscale vortex and the development of low-level jets,the confrontation between the cold and warm streams and the southward movement of the cold front,and the eastward movement of the vortex center.②There were four main warm and wet transport channels in the middle and lower layers of the process,which made the water vapor flux in the heavy precipitation area over 800 kg/(m·s)and PWV(Precipitable Water Vapor)over 70 mm.③During the heavy rainfall period,the positive vorticity center and the negative velocity center basically coincided,the frontogenesis was enhanced,and the vertical ascending motion was strong,the vertical velocity at the lower level reached-7.1 Pa/s.④During the heavy rainfall period,theθ_(se) energy front zone was formed near the terrain transition zone,the high-energy tongue was formed in the vertical direction,and the center of 800 hPaθ_(se) reached over 360 K.⑤The combination of mesoscale topography and jet stream formed a mesoscale temperature and humidity frontal zone of“northwest cold and dry,southeast warm and wet”.The terrain played a role in blocking the uplift and triggering so that heavy rainfall appeared in the front of the mountain.The research results could provide a basis for formulating regional water management strategies during

关 键 词：极端降水 超低空急流 边界层冷空气 中尺度锋区 地形作用 HYSPLIT后向轨迹模式 宜昌市 

分 类 号：P426.6[天文地球—大气科学及气象学]