2015年梅雨期长江下游地区两次暴雨天气过程的成因对比分析  

Causes of Two Heavy Rains along the Yangtze River in Jiangsu During Meiyu Period in 2015

作　　者：蒋骏[1] 黄文彦[1] 吴建秋[1] 吴晶璐 

机构地区：[1]常州市气象局,江苏常州213022

出　　处：《气象与减灾研究》2016年第4期260-268,共9页Meteorology and Disaster Reduction Research

基　　金：常州市科技项目(编号:CE20155037)

摘　　要：利用基本气象站观测资料、ECMWF ERA资料和NCEP FNL资料,通过对强降雨时刻的多种物理量场诊断,分析了2015年梅雨期发生在江苏省沿江地区的6月16—17日和27—29日两次大暴雨的形成原因。结果表明,两次大暴雨过程均发生在西太平洋副热带高压稳定维持、西南气流强盛、高层有冷空气不断入侵的大环流背景下,受中低层江淮切变线和西南急流共同影响,冷暖空气一直在沿江一带交汇,造成沿江地区持续强降水过程。两次大暴雨发生时32°N附近梅雨锋很明显,锋面随着高度的升高向北侧冷区倾斜,强降水主要位于梅雨锋南侧的暖区内。该侧700 hPa高度层以下湿位涡为负值表明大气为对流不稳定,且随着降水的发生,中层有弱冷空气入侵,使得大气的对流不稳定性进一步加强。强的降水区主要位于低空急流的左侧和高空急流的入口区右侧,高低空急流的这种配置带来了风场高层辐散、低层辐合,有利于垂直上升运动加强。同时低层暖平流和中高层正的相对涡度平流交汇于32°N附近,也有利于暴雨区的上升运动加强。暴雨区与850 hPa水汽通量散度负值中心相吻合,表明低层西南急流为暴雨区源源不断地提供水汽。Based on basic meteorological observation data,ECMWF ERA reanalysis data and NCEP FNL analysis data,the causes of the two heavy rains in Jiangsu during Meiyu period in2015 were analyzed by diagnosing the multiple physical quantities.The results showed that the two heavy rain occurred under the circulation background of stable subtropical high,strong southwest wind and the cold air intrusion in high level.Cold and warm air met alone the Yangtze River and resulted in persistent heavy rainfall along the Yangtze River region because of low-level shear line and southwest jet over Jianghuai region.The Meiyu front was strong near 32°N and tilted to the north cold region with height when the two heavy rains occurred.Heavy rainfall mainly occurred in the warm region locating at the south side of Meiyu front,in where the moist potential vorticity was negative below700 hPa which meant that the atmosphere was unstable.With the occurrence of precipitation,the weak cold air intruded in middle level and strengthened the air convective instability.The heavy rainfall was mainly located in the left side of low level jet and the right side of high level jet entrance.The configuration of high and low level jet caused wind divergence inhigh level and convergence in low level,which strengthened the upward motion.The warm advection in low level and positive relative vorticity advection in middle and upper level intersected at 32°N,which was also beneficial to strengthen the upward motion of the rainstorm area.The negative center of moisture flux divergence at 850 hPa was coincident with the heavy rain region,indicating low-level southwest jet continued to transport water vapor for torrential rain area.

关 键 词：暴雨 梅雨锋 湿位涡 急流 涡度平流 

分 类 号：G255.2[文化科学—图书馆学]