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齐铎, 崔晓鹏, 邹强利. 2023. 2020年“6·26”冕宁致灾暴雨成因观测分析[J]. 大气科学, 47(2): 585−598. doi: 10.3878/j.issn.1006-9895.2206.21149
引用本文: 齐铎, 崔晓鹏, 邹强利. 2023. 2020年“6·26”冕宁致灾暴雨成因观测分析[J]. 大气科学, 47(2): 585−598. doi: 10.3878/j.issn.1006-9895.2206.21149
QI Duo, CUI Xiaopeng, ZOU Qiangli. 2023. Observational Analysis of the Causes for the Heavy Rainfall Case in Mianning on 26 June 2020 [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 47(2): 585−598. doi: 10.3878/j.issn.1006-9895.2206.21149
Citation: QI Duo, CUI Xiaopeng, ZOU Qiangli. 2023. Observational Analysis of the Causes for the Heavy Rainfall Case in Mianning on 26 June 2020 [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 47(2): 585−598. doi: 10.3878/j.issn.1006-9895.2206.21149

2020年“6·26”冕宁致灾暴雨成因观测分析

Observational Analysis of the Causes for the Heavy Rainfall Case in Mianning on 26 June 2020

  • 摘要: 利用多源观测数据,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热带高压西进,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,促进低涡发生、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条件,决定降水起止。(2)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,灵山寺站附近不断有质心(回波强度超过50 dBZ)高度较低的强回波单体生消,降水强度显著增强。

     

    Abstract: An heavy rainfall event occurred in Mianning on 26 June 2020, inducing mountain torrents (MTs). Here, using various observational data and ERA5 reanalysis data, the causes for the event is studied from aspects of atmospheric circulation, moister conditions, local stratified characters, evolution of convective systems, and orographic effect. The results indicated that: (1) The 500-hPa situation changed little during the rainstorm. The southwesterly wind accelerated due to the tiny westward West Pacific subtropical high and the eastward mid-latitude tough and affected Sichuan Province. The forming and developing of a basin vortex (BV) can be explained well by the clockwise aspect change of ageostrophic wind at the northern part of BV. The convergence of the western BV’s northerly wind and the Panxi Plateau’s southwesterly wind changed the local dynamic and moister condition of rainfall region and determined the occurrence and development of the rainstorm. (2) The rainstorm process can be divided into two stages: In the first stage, the southwesterly wind can break the convective inhibition via the orographic lift, cold pool lift, and convergence at the mid-level troposphere. The deep convection formed on the southwest side and moved to the LSS (Lingshansi station) with heavy rain. In the second stage, the southwesterly flow was uplifted higher by the orographic and cold air associated with the Sichuan basin than the first stage. The strong convective cells occurred incessantly near LSS with the maximum reflectivity of >50 dBZ closed the melting level and caused high rainfall intensity.

     

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