河北廊坊冰雹天气特征统计分析

Statistical Analysis of Hail Event Characteristics in Langfang of Hebei Province

利用1964 2015年气象观测资料对河北廊坊冰雹天气的时空分布特征进行分析,并利用MICAPS资料、北京探空资料及多普勒雷达资料研究了廊坊冰雹日的天气形势、物理量特性及雷达回波特征。结果表明:廊坊冰雹日数整体呈下降趋势,20世纪80年代末至90年代初降雹达到高峰期。冰雹天气主要发生在15 19时,多持续1~5 min。廊坊冰雹有明显的地域特征,西北部较多。降雹日500 h Pa环流形势有4类,并对应3种地面形势。对预报冰雹天气有指导意义的物理量参数阈值为:冰雹开始前对流层中下层存在逆温层或等温层;对流参数SI指数或LI指数<0,中低层假相当位温随高度减小;0℃层高度多为3050~4702 gpm,-20℃层高度多为5996~8332 gpm,850 h Pa与500 h Pa温差为27~32℃,低层有大的垂直风切变,近地面925 h Pa垂直风切变为5.5~15.0 m·s-1·km-1。此外,廊坊冰雹云回波有块状单体和飑线两种结构,回波中心强度普遍大于60 d Bz,垂直结构上均有悬垂回波,速度场为逆风区或旋转速度>12 m·s-1的弱切变,VIL普遍大于35 kg·m-2,ET普遍大于11 km。

Based on the meteorological observation data from 9 stations in Langfang of Hebei province from 1964 to 2015,the temporal and spatial distribution of hail weathers in Langfang was analyzed in detail. Then the circulation patterns,physical parameters and radar echo characteristics in hail days were analyzed by using the MICAPS data,sounding data at Beijing station and Doppler radar data.The results displayed that the overall trend of hail events had declined remarkably,the hail weather occurred frequently in the late 1980 s and early 1990 s. In a day,hail mainly occurred from 15： 00 to19： 00,and lasted 1 5 min. Hail in Langfang has obvious regional characteristics,most in the northwest.The typical 500 h Pa circulation patterns of hails could be divided into 4 types,accompany with 3 kinds of surface circulation patterns. The physical parameters thresholds with prediction significance are as follows：prior to hail there are temperature inversion or isothermal layer at the middle and lower troposphere,and convection parameter SI or LI is less than 0,the pseudo-equivalent potential temperature at middle and low level decreases with height,the 0 ℃ environmental temperature height is between 3050 4702 gpm,the-20 ℃ environmental temperature height is between 5996 8332 gpm,the temperature difference between 500 h Pa and 850 h Pa is between 27 32 ℃,there are large wind shear at lower levels,the wind shear between near ground and 925 h Pa is 5. 5 15. 0 m·s^-1·km^-1. There are 2 kinds of hail cloud echo structure,block monomer and squall respectively,the intensity of radar echo centers are more than 60 d Bz,the vertical sections are all characterized by overhang structure,the velocity field displays adverse wind area or weak shear with 12 m·s^-1 rotational speed,the vertical integration of liquid water（VIL）content was more than 35 kg·m^-2 and echo top（ET） height was more than 11 km.