盛夏一次地面冷锋过境引发局地大暴雨的成因分析  

Analysis on the local heavy rainfall caused by cold front in midsummer

作　　者：尉英华[1] 陈宏[1] 刘一玮[1] 林晓萌 WEI Yinghua;CHEN Hong;LIU Yiwei;LIN Xiaomeng(Tianjin Meteorological Observatory,Tianjin 300074)

机构地区：[1]天津市气象台,天津300074

出　　处：《暴雨灾害》2021年第4期393-400,共8页Torrential Rain and Disasters

基　　金：国家自然科学基金项目(41575049);中国气象局预报员专项(CMAYBY2020-008,CMAYBY2020-009)

摘　　要：利用常规观测资料、风廓线雷达和变分多普勒天气雷达分析系统(VDRAS)反演资料,从大气环流形势、垂直结构特征和对流发生发展机制等方面,对2017年7月21日地面冷锋后华北地区发生的一次局地大暴雨过程成因进行探讨。结果表明:(1)局地大暴雨发生在副热带高压北抬、低层回流冷空气侵入的背景下,暴雨区位于地面冷锋后约300 km的冷空气一侧,850 hPa低空切变线是主要的影响系统。(2)在低层回流冷空气作用下850 hPa以下表现为环境温度直减率小于湿绝热递减率(γ<γs)的稳定层结;同时受副热带高压北抬影响,700-500 hPa层结不稳定性加强,不稳定层结位于边界层稳定层结之上,具有冷区“高架对流”特征。(3)低层冷垫对应下沉运动,暖湿气流上升运动位于冷垫之上,1.4 km高度附近的中尺度辐合线对高架对流的触发起到了重要作用。(4)带状中尺度对流系统东移缓慢,并呈现明显的后向传播和列车效应特征,是导致降水持续时间长并造成局地大暴雨的主要原因。Using conventional observations,wind profiling radar and the retrieval data from Variational Doppler Radar Analysis System(VDRAS),we analyzed the atmospheric circulation,thermo-dynamic structural characteristics and rainstorm triggering mechanism,and discussed the causes of a local heavy rainfall event in North China occurred behind a cold front on 21 July 2017.The results showed that the torrential rainfall occurred under the weather conditions where the subtropical high at 500 hPa was lifted northward and the return cold air in the low-level invaded.The shear line at 850 hPa was the main large-scale influencing system.The torrential rainfall was located on the cold air side about 300 km behind the surface cold front.Under the control of cold air returning in boundary layer,the atmosphere below 850 hPa presented as a stable stratification ofγ<γs.At the same time,due to the influence of the subtropical high northward,the instability of the 700-500 hPa stratum was strengthened,so the unstable atmosphere was situated over the stable cold layer,which contributed to the favorable environmental conditions for"elevated convection".Corresponding to the sinking movement of the low-level cold air,the rising motion of warm and humid air was above the cold layer,and the meso-scale convergence line near the 1.4 km height played an important role in triggering the elevated convection.We further found that the belt-shaped meso-scale convective system moved slowly to the east,and it had obvious characteristics of back-propagation and train effect,which was the main reason for the long duration of the heavy rainfall.

关 键 词：高架对流 冷垫 列车效应 后向传播 

分 类 号：P458.121.1[天文地球—大气科学及气象学]