田泽芸 李丽平 胡振菊

摘要 利用NCEP/NCAR再分析資料，通过对2012年7月中旬我国中东部地区持续性强降水过程中东亚夏季风系统中主要成员的时空变化特征进行分析。结果表明，此次持续性强降水期间，副高北界、南亚高压脊线及中纬度锋区位置相对稳定，长江中下游地区一直处于南亚高压反气旋环流东侧偏北风与西风槽前偏南风之间的风向开口辐散区中；副高南撤时，强降水主要位于584 dagpm线北侧，副高北抬时，强降水主要位于584 dagpm线南侧；此次持续性强降水发生前期，大气为上干下湿不稳定层结，当西风带低槽频频携带冷空气南下影响，同时低空西南急流反复加强，其出口区左侧较强的风速梯度为暴雨的发生发展提供了动力条件；低层干空气的不断侵入，低槽和低涡间的垂直正反环流促使垂直上升运动维持或发展，进而造成持续性强降水；高空西风急流加强（减弱）超前低空西南急流加强（减弱）2～5 d，对持续性强降水有超前指示意义。

关键词 持续性强降水；形成机制；高、低空急流；冷空气；垂直环流

中图分类号 S161.6 文献标识码 A 文章编号 0517-6611（2014）31-11028-05

The Formation Mechanism Analysis of Continuity Strong Precipitation at the Middle East Area of China in July 2012

TIAN Zeyun1，2， LI Liping1， HU Zhenju2

（1. School of Atmospheric Sciences， NUIST， Nanjing， Jiangsu 210044； 2. Changde Meteorological Bureau of Hunan Province， Changde， Hunan 415000）

Abstract Using the NCEP/NCAR reanalysis data， the temporal and spatial variation features of the leading members of the East Asian summer monsoon system during the durative heavy precipitation at the middle east area of China in midJuly 2012 was analyzed. The results showed that， the position of North boundary of subtropical high， the south ridge line and the midlatitude frontal zone were relatively stable during the persistent heavy rainfall. Middle and lower reaches of the Yangtze River has been in the divergence zone of the northerly wind of the South and the southerly wind of the trough. When the subtropical high moving southwrad， the heavy precipitation often occured the north of the 584 line； while the subtropical high moving northwrad， the heavy precipitation often occured the south of the 584 dagpm line. Before the persistent heavy rainfall occured， the atmosphere was unstable stratification.The cold air of westerly trough frequently carried and the warm air of the Southwest Jet at low altitude repeatedly carried， which the strong wind speed gradient of the left of exit region has provided the impetus for the development of storm conditions.The intrusion of dry air at lowlevel， the front and back vertical circulation of the trough and the Vortex maintained the upward vertical movement， and the persistent heavy rainfall had developed. Upperlevel westerly jet strengthened （weakened） before Southwest Jet at low altitude to strengthened （weakened） for 2-5 d， that had a ahead of significance for durative heavy precipitation.

Key words Persistent heavy rain； Formation mechanism； Upper and lowerlevel jets； Cold air； Vertical circulation

强降水引发的城市内涝、山体滑坡及泥石流等，给人们的生活生产均造成了一定的危害，而持续性强降水天气对社会的影响更大。不少学者对各类强降水天气过程进行了归纳总结，杨荆安等分别对2008～2013年汛期全国当年主要暴雨过程进行了总体概述^[1-7]。许多学者也分别从强降水产生机制、物理量特征以及预报指标探讨等方面进行了一定的研究^[8-9]，尤其是对于持续性强降水研究^[10-13]，如徐双柱等通过分析一次湖北省持续性暴雨发现，中尺度对流回波或云团一般发生在多个天气尺度系统的汇合处^[10]；……