摘要
受河套低槽和低涡切变的共同影响,2022年6月26日12∶00-13∶00(北京时,下同)陕西商洛境内商南县西部的金丝峡出现了极端短时强降水(简称“6.26”过程),小时雨强高达108.3 mm·h^(-1),是一次典型的由中尺度新生雷暴引发的局地强降水过程。局地性和突发性强、持续时间短、降水强度大,各家业务模式均出现漏报。本文基于常规气象观测资料及加密自动站观测资料、多普勒天气雷达资料与欧洲中期天气预报中心第五代大气再分析资料(ERA5),对此次短时强降水成因进行了详细分析。结果表明:(1)该过程发生在500 hPa河套低槽配合700 hPa低涡切变缓慢东移的环流背景下,商南地区动力抬升条件和能量条件较好,对流发生前K指数达到42.83℃。(2)局地充沛的水汽加之低层较强的垂直上升运动可将水汽迅速向上输送,有利于在金丝峡形成极端短时大暴雨。(3)金丝峡附近热力非均匀下垫面造成的局地环流和变压风引起的局地流场之间形成的中小尺度地面辐合线是导致金丝峡极端短时强降水的主要原因。金丝峡特殊的河谷地形,一方面有利于触发对流,另一方面阻挡了低层东南气流沿山爬坡抬升,进一步加强了金丝峡上空大气的辐合,促使暴雨增幅。
Affected by the Hetao trough and low vortex,an extreme short-term heavy rainfall(referred to as the"6.26"event)occurred on 26 June 2022 from 12∶00 BT to 13∶00 BT in the western part of Shangnan County in Shaanxi province.During this process,an hourly rainfall of up to 108.3 mm was observed.This event was a typical local heavy rainstorm event caused by a newly-born mesoscale thunderstorm,which was characterized by its localized,sudden,short duration,and high-intensity precipitation.All numerical models failed to predict this event.Based on the data from conventional meteorological observations,encrypted automatic weather stations,Doppler weather radar,and the fifth-generation atmospheric reanalysis data of the European Center for Medium-Range Weather Forecasting(ERA5),this study analyzed in detail the environmental field characteristics and convective triggering mechanisms of this short-time heavy precipitation event.The results are as follows:(1)This event occurred under a combined circulation background of the 500 hPa low trough in Hetao and 700 hPa low vortex shear slowly moving eastward.The dynamic uplift and energy conditions over Shangnan were favorable,and the K-index reached 42.83℃ before the convection occurred.(2)The local abundant water vapor and the strong vertical upward movement at the lower level could rapidly transport the water vapor upward,which was conducive to the formation of short-term heavy rain over Jinsi Gorge.(3)The small and medi⁃um-scale surface convergence line formed between the local circulation caused by the thermal heterogeneity underlying surface near Jinsi Gorge and the local flow field caused by variable pressure wind is the main reason for the extremely short-term heavy precipitation in Jinsi Gorge.In this process,the special valley terrain of Jinsi Gorge played a significant role.On the one hand,it triggered the generation of convec⁃tion.On the other hand,because of its block,the low-level southeast airflow rose along the mountain slope.This further strengthened the con⁃vergence of the atmosphere over Jinsi Gorge,which finally enhanced the precipitation of this rainstorm.
作者
刘嘉慧敏
潘留杰
郭大梅
屈丽玮
吉庆
郑然
LIU Jiahuimin;PAN Liujie;GUO Damei;QU Liwei;JI Qing;ZHENG Ran(Shaanxi Meteorological Observatory,Xi’an 710014;Key Laboratory of Eco-Environment and Meteorology for the Qinling Mountains and Loess Plateau,Xi’an 710044;The Climate Center in Sichuan Province,Chengdu 610072)
出处
《暴雨灾害》
2023年第6期659-669,共11页
Torrential Rain and Disasters
基金
陕西省自然科学基础研究计划项目(2022JQ-279)
中国气象局复盘总结专项(FPZJ2023-129)。
关键词
局地暴雨
新生雷暴
中尺度辐合线
地形作用
local heavy rain
newly-born thunderstorm
mesoscale convergence line
topographical action
