双月刊

ISSN 1006-9895

CN 11-1768/O4

2020年“6.26”冕宁致灾暴雨成因观测分析
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中国科学院大气物理研究所云降水物理与强风暴重点实验室

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中国科学院战略性先导科技专项(A类)资助 XDA23090101,中国气象局沈阳大气环境研究所基本科研业务费重点项目 2020SYIAEZD4


Observational analysis of the heavy rainfall case on June 26, 2020, in Mianning
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Key Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS), Institute of Atmospheric Physics, Chinese Academy of Sciences

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    摘要:

    利用自动站、探空、雷达等观测数据,结合ERA5再分析资料,从环流背景、水汽条件、局地探空特征、对流系统演变以及地形影响等方面,分析了“6.26”冕宁致灾暴雨的可能成因。结果表明:(1)暴雨期间,500 hPa环流形势相对稳定,伴随中纬度槽东移和副高西进,二者间西南气流显著增强,影响四川地区;盆地低涡北部非地转风风向随时间顺时针变化,使夜间向低涡中心辐合的气流增强,促进低涡发展;盆地低涡西部的偏北气流和攀西高原的西南气流同时增强,使局地环流发生变化,改变降水区低层动力和水汽辐合条件,决定降水起止。(2)因对流触发原因不同,可将冕宁暴雨过程分为两个阶段:前期,受地形和冷池出流抬升影响,以及叠加其上的中层辐合的接力抬升作用,西南暖湿气流冲破对流抑制,在灵山寺西南侧山前形成强对流单体,强对流单体随引导气流向东北移动到灵山寺站,带来强降水;后期,受山前地形阻挡和山后源自盆地的冷空气的共同作用下,西南暖湿气流辐合上升运动的强度和伸展高度同时增加,水汽辐合加强,灵山寺站附近不断有质心高度较低的强回波单体生消,降水强度显著增强。

    Abstract:

    An unpredicted heavy rainfall event with a maximum 8-hr accumulated rainfall exceeding 180 mm and a maximum hourly rate of 69.3 mm h-1 occurred in Mianning on June 26, 2020, inducing mountain torrents (MTs). Here, this event is studied using various observational data. The results indicated that (1) the favorable upper and lower circulation and terrain leaded to the rainstorm event. During the rainstorm, the situation at 500 hPa had little change. With the tiny westward west-Pacific subtropical high (WPSH) and the eastward mid-latitude tough, the sourthwestly wind accelerated. The forming and developing of basin vortex (BV) can be explained well by the aspect change of ageostrophic wind. The convergence between the northly wind of western BV and the sourthwestly wind in Panxi Plateau determined the occurrence and development of rainstorm. (2) The rainstorm process can be divided into two stages: The first stage, the south branch of the updraft reached to the upper troposphere by the orographic lift, cold poo lift and convergence at the mid-level troposphere. The second stage, the south branch flow was uplifted by the orographic and the cold air associated with Sichuan basin. The maximum reflectivity over 50 dBZ closed the melting level on account of the maximum vertical velocity location descended during the period of large rainfall intensity in LLS. The maximum VIL over 50 kg/m2 means the high?precipitation efficiency and rain intensity.

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  • 收稿日期:2021-08-08
  • 最后修改日期:2022-06-08
  • 录用日期:2022-07-20
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