两次大暴雨过程天气形势与物理量场对比分析

Comparison of weather situation and physical quantity field during two large rainstorms

使用常规天气图、NCEP1×1°的再分析资料,针对2010年5月13日和5月21日江西2次大暴雨天气过程,从天气形势场、影响系统和物理量场等方面进行对比分析,结果表明:2次暴雨天气过程具有相似的基本特征,其共同点是高纬度冷空气以短波槽形式频繁南下,提供了暴雨发生的环境背景条件;低涡切变东移和辐合区的持续存在是提供动力抬升的有利条件;西南急流和中低层强大的水汽通量以及水汽通量辐合中心建立,提供了有利的水汽条件;2次暴雨的不同点是在暴雨发展过程中,低涡切变等影响系统的位置、螺旋度的强度以及其它物理量,决定着暴雨的降水强度;5月13日大暴雨过程中各项物理量指标均比5月21日大暴雨过程强而典型,但降水量却小于5月21日,表明锋前暖区中强对流性降水是产生大暴雨的重要条件。

By use of conventional weather maps and NCEP 1×1° reanalysis data,aiming at two large rainstorms in Jiangxi on 13th and 21th May 2010,the weather situation,influence system and physics field were compared.The results showed that：there were similar basic characteristics in two processes that was the cold air in high latitude frequently moved toward south by way of short-wave trough,which provided environmental background for the heavy rainfall;the eastward of low vortex shear and the continued existence of convergence area provided a favorable dynamic lifting condition;the strong water vapor flux of southwest jet in low-level clould as well as the establishment of water vapor flux convergence center provided a favorable moisture condition;the difference between the two large rain storms is the location of influence systems,such as low vortex shear,intensity of helicity and other physical quantities,which determined the intensity of heavy rainfall;the physical indices of ＂5.13＂heavy rain were more strong and typical than that of ＂5.21＂ heavy rain,but rainfall was less than that of ＂5.21＂,which indicated that the strong convective precipitation in frontal warm sector was an important condition to produce heavy rain.