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气象:2013,39(7):848-860
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“12.7.22”四川暴雨的MCS特征及对短时强降雨的影响
(1.中国气象局成都高原气象研究所,成都 610072;2.四川省气象台,成都 610072)
Characteristics of Mesoscale Convective System and Its Effects on Short-Time Severe Rainfall in Sichuan Basin During 21-22 July 2012
(1.Institute of Plateau Meteorology, CMA, Chengdu 610072;2.Sichuan Meteorological Observatory, Chengdu 610072)
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投稿时间:2013-01-23    修订日期:2013-05-16
中文摘要: 利用FY2D卫星云图云顶亮温(TBB)资料、雷达回波产品和常规气象观测资料、地面自动站降水资料及NCEP 1°×1°逐6 h再分析资料,对2012年7月21—22日四川暴雨中的中尺度对流系统(MCS)特征及其对短时强降雨影响进行分析,结果表明:(1)这次暴雨过程在21日00—06时和21日21时至22日03时有两个明显的6 h短时强降雨阶段。第一阶段中,500 hPa高原涡与700 hPa低涡切变线、低空急流作用,引发盆地西部短时强降雨;第二阶段中,500 hPa高原涡与700 hPa西南涡作用,引发盆地南部短时强降雨。(2)短时强降雨通常由MCS中的深对流特征造成,水平尺度多为β中尺度或更小的γ中尺度系统,具有云顶亮温低、雷达反射率因子大和垂直累积液态水含量高等特点。(3)探空资料分析表明,MCS增长初期,大气不稳定能量高,存在风垂直切变,在低层冷暖平流交汇明显且温度梯度大的区域,有利于激发MCS生成,另外高低层系统作用产生的深厚正涡度对其发生发展亦具有重要作用。在演变过程中MCS具有低层正涡度、负散度,高层负涡度、正散度的垂直结构,且上升速度明显,这种结构特征可能是MCS发展维持的重要因素,亦是产生强降雨的机制之一。
Abstract:Using FY2D TBB data, radar echo data, routine meteorological data, precipitation data of automatic weather stations, NCEP 1°×1° reanalysis data etc. are analyzed characteristics of mesoscale convective system (MCS) and its effects on short time extremely heavy precipitation in Sichuan Basin during 21-22 July 2012. The results show that: (1) This precipitation process has two significant 6 h short time severe rainfall stages. The first stage is from 00:00 to 06:00 BT 21 July 2012, and the second is from 21:00 BT 21 to 03:00 BT 22 July 2012. In the first stage, the short time severe rainfall in western Sichuan Basin is caused by MCS, which is affected by 500 hPa plateau vortex and 700 hPa low vortex shear line. In the second stage, the extremely heavy rain is caused by the 500 hPa plateau vortex and 700 hPa southwest low vortex. (2) Short time severe rainfalls are usually caused by deep convections in MCS. In its developing process, MCS is in meso βscale or meso γ scale, having the features of low TBB values, big radar reflectivity factors and high VIL values. (3) The analysis of sounding data shows that unstable energy of atmosphere is high, CAPE value is large and vertical wind shear is dramatic during the early stage of MCS. The interaction areas of low level cold and warm temperature advections are beneficial to induce MCS, and the temperature gradient is high in these areas. Also during different developing periods, the structure of MCS shows positive vorticity and negative divergence in low level, while negative vorticity and positive divergence exist in high level. Such physical structure is an important factor for MCS to develop and maintain, and it is also one physical mechanism for short time severe precipitation.
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基金项目:国家自然科学基金面上项目(41275051)、中国气象局预报员专项(CMAYBY2013-057)、公益性行业(气象)科研专项(GYHY201106003和GYHY201206042)及四川省气象局青年基金(川气课题2012-青年-01)共同资助
引用文本:
陈永仁,李跃清,2013.“12.7.22”四川暴雨的MCS特征及对短时强降雨的影响[J].气象,39(7):848-860.
CHEN Yongren,LI Yueqing,2013.Characteristics of Mesoscale Convective System and Its Effects on Short-Time Severe Rainfall in Sichuan Basin During 21-22 July 2012[J].Meteor Mon,39(7):848-860.