江西省三类强对流天气环境物理量对比分析

利用2001—2010年89个国家级地面观测资料和NCEP 1°×1°再分析资料,分别从水汽条件、动力特征、0℃层和-20℃层的特征高度以及大气不稳定条件等方面,对江西省三类典型的强对流天气(冰雹、雷暴大风及短时强降水)的特征进行统计分析,从而给出江西省地区这三类强对流天气过程主要预报物理量的分布特征及阈值区间,为江西省精细化的强对流天气预报提供参考指标。结果表明:1三者对比,强降水具有更深厚的"湿"对流特征,冰雹多具有上干下湿的"干"对流特征;2低层辐合、高层辐散条件中,短时强降水高于冰雹和大风,表现为短时强降水低层辐合中位数为-17×10-5s-1,高层辐散中位数为14×10-5s-1,对应冰雹和大风低层辐合都为-14×10-5s-1,高层辐散都为10×10-5s-1;风垂直切变值,冰雹最大,大风次之,强降水最弱,具体表现为500 h Pa到1 000 h Pa风速差中位数冰雹为18 m/s,大风为17 m/s,强降水为11 m/s;3不稳定条件方面,冰雹的对流有效位能、抬升指数以及850 h Pa与500 h Pa温差中位数分别为2 651 J·kg-1;-6℃、26℃,远远强于强降水的735 J·kg-1;-2℃、23℃,大风对应中位数为1 924 J·kg-1;-5℃、25℃,介于冰雹和强降水之间;4特征高度0℃层和-20℃层冰雹最低、大风次之、强降水最高,4 800 m和7 700 m可以作为0℃层和-20℃层冰雹和强降水的分界线。当对应高度大于该值时有利于强降水的出现,小于该值有利于冰雹的出现;5不稳定条件和动力条件具有互补关系,两者中其一出现极有利条件时,在江西省的实际预报业务中,就要考虑强对流天气的发生,当一条件异常偏大(很有利条件),另一条件不是很有利情况下,也有可能出现强对流天气。

Comparative study of three types of convective events in Jiangxi

This study analyzed the environmental conditions of hail, thunderstorm and heavy rainfall greater than 30mm per hour in Jiangxi Province during 2001 to 2010 by using 89 station observation data and NCEP Reanalysis in 1*1 resolution. The results shown that: (1) Compared to hail and thunderstorm, the heavy rainfall is characterized by the strongest moisture supply and the deepest moist convective structure. The hail events are featured on dry upper layer and wet lower part. (2) Heavy rainfall is accompanied with more upper divergence and lower convergence, while hail with more vertical shear. (3) For unstable conditions, hail (heavy rainfall) events are associated with biggest (smallest) values of CAPE, convective index, temperature difference between 850hPa and 500hPa, except the K index. (4) The height of 0C and -20C higher (lower) than 4800m and 7700m favor the developing of heavy rainfall (hail) events. (5) There are two groups of convection factors, unstable conditions (such as CAPE and temperature difference between 850hPa and 500hPa) and dynamical condition (such as vertical shear). It is possible that convective system will developing by one favorable factor even if the other is unfavorable.