四川盆地2020年“8.11”特大暴雨过程中尺度系统演变特征  

EVOLUTION CHARACTERISTIC OF MESOSCALE SYSTEM DURING “8.11”, 2020 TORRENTIAL RAIN IN SICHUAN BASIN

作　　者：周春花 肖递祥[2,4] 郁淑华 ZHOU Chunhua;XIAO Dixiang;YU Shuhua(Sichuan Meteorological Disaster Prevention Technology Center,Chengdu 610072,China;Sichuan Meteorological Observatory,Chengdu 610072,China;Chengdu Institute of Plateau Meteorology,Chengdu 610072,China;Heavy Rain and Drought-Flood Disaster in Plateau and Basin Key Laboratory of Sichuan Province,Chengdu 610072,Chin)

机构地区：[1]四川省气象灾害防御技术中心,四川成都610072 [2]四川省气象台,四川成都610072 [3]中国气象局成都高原气象研究所,四川成都610072 [4]高原与盆地气象灾害四川省重点实验室,四川成都610072

出　　处：《热带气象学报》2022年第6期812-824,共13页Journal of Tropical Meteorology

基　　金：国家自然科学基金重点项目(91937301);中国气象局创新发展专项(CXFZ2021Z033)子项目:2020年盛夏四川盆地二次致洪暴雨过程分析;成都市气象局影响预报创新团队建设;高原与盆地暴雨旱涝灾害四川省重点实验室发展基金项目(SCQXKJZD2020006)共同资助。

摘　　要：针对2020年8月11—12日四川盆地西部特大暴雨过程中尺度系统演变特征和维持机制,利用欧洲中心ERA5逐小时再分析资料以及FY-4A的云顶相当黑体温度TBB资料进行诊断分析。(1)本次过程发生在500 hPa巴湖长波槽分裂短波和高原低槽东移发展在四川盆地停滞,副高加强西伸形成阻挡的形势下,同时200 hPa有南亚高压和高空分流区配合。(2)在上述有利的背景条件下,中尺度系统活动经历了中尺度辐合扰动-西南涡生成发展-低空急流影响-西南涡再次发展增强等4个阶段,西南涡两个阶段的发展对降水影响最大,初生发展阶段雨强最强,再次发展阶段强降雨范围最大。(3)西南涡在暖区内初生发展,对流不稳定性强,地面潜热和感热加热以及500 hPa层以下水汽凝结潜热加热均十分显著,在较强暖湿平流作用下,配合低层涡度拉伸项和扭转项的动力作用加强,西南涡迅速发展,但低层辐合相对较弱,正涡度柱高度仅发展至500 hPa。(4)西南涡再次发展阶段冷平流入侵,大气斜压性增强,中高层感热和凝结潜热加热作用加大,“低层辐合-中高层辐散”的动力机制显著加强,配合垂直向上输送正涡度和涡度拉伸项的动力发展作用,西南涡发展旺盛,正涡度柱中心强度和发展高度较初始发展阶段均明显增强。To study the evolution characteristics and maintenance mechanism of the mesoscale system during the extremely heavy rainstorm occurred during August 10—12, 2020 in the western Sichuan Basin,the present study used the ERA5 hourly re-analysis data from the European Center and the FY-4A-TBB data for analysis, and the conclusions are as follows:(1) This process occurred when short wave was split from the 500 hPa Balkhash Lake long wave trough, the plateau low trough moved eastward and stalled over the Sichuan Basin and the subtropical high strengthened westward and became an obstruction.Simultaneously, there was the South Asian high pressure and the high-altitude diversion area at the 200hPa layer.(2) Due to the aforementioned favorable conditions, the mesoscale system experienced four key stages: mesoscale convergence disturbance, Southwest vortex generation and development, low-level jet influence, and Southwest vortex redevelopment and enhancement. The two development stages of the Southwest vortex had the greatest impact on precipitation. The rainfall intensity was the strongest during the initial development stage, and the range of heavy rainfall became the largest during the redevelopment stage.(3) The Southwest vortex developed within the warm region with strong convective instability. On the ground, the latent heat and sensible heat heating as well as the latent heat heating of water vapor condensation below the 500 hPa layer was very significant. Under the influence of relatively strong warm and wet advection, the Southwest vortex developed rapidly with the strengthening of the dynamic action of the low-level vorticity stretching term and torsional term. In contrast, the low-level convergence was relatively weak. The height of positive vorticity column only developed to the 500 hPa layer.(4) At the redevelopment stage of the Southwest vortex, there was cold advection invasion and atmospheric barotropism enhancement, and heating effect of sensible heat and latent heat of condensation in middle and high leve

关 键 词：西南涡 中尺度系统 正涡度 热源 涡度平流 

分 类 号：P426.62[天文地球—大气科学及气象学]