一次四川盆地低涡型特大暴雨过程分析

Analysis on a Heavy Vortex Rainstorm in Sichuan Basin from 29 June to 2 July 2013

利用NCEP 1°×1°再分析资料和地面加密自动站、实况探空资料及FY-2E的TBB资料,分析2013年6月29日至7月2日四川盆地特大暴雨过程持续时间久、强度强的原因。结果表明:(1)本次盆地暴雨属于低涡型暴雨过程,高原低涡和西南低涡是这次持续性特大暴雨过程的直接影响系统,有利的环流场引导高原低涡及西南低涡东移并形成阻塞,使其稳定在盆地;(2)西南急流的建立及维持为降水区提供了大量的水汽和不稳定能量,并使得中尺度系统得以维持和发展;(3)强烈的高空辐散以及高原低涡和西南低涡共同作用,使得盆地低层正涡度维持并形成上升气流柱,这是强降水发展维持的重要条件;(4)盆地低涡的持续维持诱发了中小尺度云团稳定加强,遂宁站的小时雨强与其对应TBB低值有很好的对应关系;(5)从乐至附近不断产生的强回波单体发展并向东北方向移动,在遂宁一带形成强回波带,形成的类似"列车效应"是造成遂宁地区产生特大暴雨的主要原因。并且强回波带中中气旋的长时间存在意味着对流系统不会很快消弱。

Based on NCEP 1° × 1° reanalyzed data,the intensive meteorological observation stations data,sounding data and FY- 2E satellite cloud images,the persistent and exceptionally severe rainstorm process which occurred in Sichuan Basin from 29 June to 2 July2013 was analyzed. Results are as follows：（ 1） The plateau low vortex and Southwest China low vortex were the direct influencing systems of this heavy rainstorm,the advantageous circulation field led the two low vortexes moving eastward and being stable over Sichuan Basin.（ 2） The setting up and maintaining of southwest jet provided abundant water vapor and unstable energy for rainfall area,and made middle scale system maintain and develop.（ 3） The intense divergence on up level and common effect of the plateau low vortex and Southwest China low vortex made positive votex maintain on low level and ascending airflow form over the Sichuan Basin,which was the important condition for genesis and development of the heavy rainfall.（ 4） The sustaining maintaining of low votex over the basin urged mesoscale convective cloud clusters to be stable and developing,and hourly rainfall intensity at Suining station well corresponded to TBB values.（ 5） The large area precipitation echo passing from Lezhi to Suining formed the＂train effect＂and resulted in the heavy rainfall. The mesoscale cyclone occurring on the precipitation echo band was the direct reason of the local heavy rainstorm.And this mesoscale cyclone lasted long time,which showed that connection system didn’t decrease speedily.