一次西北涡诱生气旋引发秦巴山区大暴雨的成因分析  

Cause Analysis of a Heavy Rainstorm in Qinba Mountains Triggered by the Induced Cyclone of Northwest Vortex

作　　者：肖贻青 杜怡心 欧阳雨 杜一博 陈欣昊 谭新龙 XIAO Yiqing;DU Yixin;OUYANG Yu;DU Yibo;CHEN Xinhao;TAN Xinlong(Heavy Rainfall Research Center of China,Wuhan 430070,China;Shaanxi Provincial Meteorological Observatory,Xi’an 710014,China;Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province,Chengdu 610072,China;Shaanxi Provincial Institute of Meteorological Science,Xi’an 710016,China;Xi’an Meteorological Service,Xi’an 710016,China;Inspur Yunzhou Industrial Internet Co.,Ltd,Jinan 250101,China)

机构地区：[1]全国暴雨研究中心,武汉430070 [2]陕西省气象台,西安710014 [3]高原与盆地暴雨旱涝灾害四川省重点实验室,成都610072 [4]陕西省气象科学研究所,西安710016 [5]陕西省西安市气象局,西安710016 [6]浪潮云洲工业互联网有限公司,济南250101

出　　处：《高原山地气象研究》2024年第4期30-40,共11页Plateau and Mountain Meteorology Research

基　　金：暴雨开放基金项目(BYKJ2024Q03);高原与盆地暴雨旱涝灾害四川省重点实验室开放研究基金项目(SZKT202210);中国气象局暴雨精细化分析和预报青年创新团队(CMA2023QN05);中国气象局复盘总结专项(FPZJ2024-134)。

摘　　要：基于常规观测、ERA-5再分析和FY-4A卫星等资料,研究了2020年8月6—7日一次西北涡诱生气旋引发秦巴山区大暴雨过程的中尺度环境特征,并利用位势涡度(Potential Vorticity,PV)和Okubo-Weiss参数(OW)定量分析了诱生气旋的生成发展过程。结果表明:此次大暴雨过程是在西北涡诱生气旋作用下由中尺度对流系统(Mesoscale Convective System,MCS)引发,强降水基本位于中尺度对流云团云顶亮温的冷中心及后部偏西北气流一侧的亮温梯度大值区。在诱生气旋生成前,西北涡后部的偏北气流与西太副高外围的西南气流形成中尺度切变线,在秦巴山区触发产生一些无组织的对流单体,降水强度较小;诱生气旋生成后,秦巴山区水汽辐合加剧,尤其是对流层中低层十分显著,同时正涡度和垂直上升运动增强,触发该区域对流不稳定,从而使多个β和α-中尺度对流云团合并发展为MCS,在缓慢东移过程中带来大范围强降水。此次过程的诱生气旋是在有利的高低空形势配合下,受500 hPa低槽引起高位涡向下传递强迫和700 hPa OW大值引起气旋性涡度增加的共同影响,西北涡后部偏北气流与西太副高外围西南气流的气旋性运动加强形成的涡旋环流,且500 hPa位涡和700 hPa OW参数的垂直耦合可使诱生气旋发展为较强的涡旋系统,进而导致强降水的发生。当位涡和OW参数同时减小后,诱生气旋的气旋性环流结构难以维持,减弱为切变线后成为西北涡的一部分。Based on conventional observational data,ERA-5 reanalysis data and FY-4A satellite data,the mesoscale environmental characteristics of a heavy rainstorm in Qinba Mountains caused by the induced cyclone of northwest vortex(NWV)on August 6—7,2020 are studied,and the development process of the induced cyclone is quantitatively analyzed by using Potential Vorticity(PV)and Okubo-Weiss(OW)parameters.The results show that the heavy rain process was caused by the Mesoscale Convective System(MCS)under the action of the cyclone induced by the northwest vortex.The heavy rainstorm was basically located in the cold center of the cloud top bright-ness temperature of the mesoscale convective cloud cluster and the large value area of the brightness temperature gradient on the side of the northwest airflow.Before the formation of the induced cyclone,the northerly airflow in the rear of the NWV and the southwesterly air-flow in the periphery of the Western Pacific Subtropical High(WPSH)formed a mesoscale shear line,which triggered some unorganized convective cells in the Qinba Mountains with low precipitation.After the formation of the induced cyclone,the water vapor transport,the positive vorticity,strong convergence and updraft at lower troposphere in Qinba mountains were significantly strengthened to trigger the convective instability,resulting in multipleβandα-Mesoscale convective cloud clusters merged and developed into MCS,which brought large-scale heavy precipitation in the process of slow eastward movement.The induced cyclone was a vortex circulation formed by the downward transmission of high vortex caused by the 500 hPa trough and the increase of cyclonic vorticity caused by the large value of 700 hPa OW under the favorable high and low altitude situation.The northerly airflow behind NWV and the cyclonic movement of the southwest airflow around the WPSH were strengthened,and the vertical coupling of 500 hPa PV and 700 hPa OW parameters could make the induced cyclone develop into a strong vortex system,which led to th

关 键 词：西北涡 诱生气旋 位势涡度 Okubo-Weiss参数 秦巴山区 

分 类 号：P447[天文地球—大气科学及气象学] P458.121.1