东北低涡槽后型河南强对流过程的天气学特征分析

Analysis on Characteristic of Severe Convective Weather in Henan in the Situation of Northeast Vortex and the Back of Trough

利用常规高空、地面观测资料和14时订正后的探空资料,分析2008—2010年6月河南处于东北低涡槽后形势下其强对流天气的相关物理量特征和阈值,通过对其中3次致灾强风暴过程的天气学特征进行综合分析,归纳出其三维天气系统要素配置和预报着眼点。结果表明:1)SI、LI均为负值,K指数≥20℃,△θse850-500≥5℃,CAPE≥1 500 J.kg-1,Sweat指数≥180,0—6 km水平风垂直切变≥15 m.s-1,大气可降水量≥2 cm,可作为发生灾害性强对流天气的参考指标;SI为正值,LI≥-1.5℃,K指数≤24℃,△θse850-500≤-4.3℃,CAPE≤150 J.kg-1且远小于CIN、14时探空订正后CAPE也在500 J.kg-1以下,0—6 km垂直风切变≤12 m.s-1,可降水量≤1.5 cm,可作为无对流天气出现的参考指标;除此之外,可出现一般雷暴天气。2)东北低涡槽后型背景下,河南出现强对流天气的热力不稳定条件是,中上层干冷,有24 h显著降温区或冷槽、冷平流;低层暖,850 hPa温度达到20℃,或有低空急流或显著流线通过暖脊。3)其抬升触发条件是,中层有横槽、切变线、干线,地面有辐合线、干线等有触发和抬升作用的系统。4)其水汽条件是,850 hPa比湿≥7 g.kg-1,地面露点温度达16℃以上。5)垂直风切变条件是,存在高空西北风急流,低层偏南风,地面偏东风。

The routine upper-air and surface observations and the revised sounding data at 14：00 were used to analyze physical quantity features and thresholds of the severe convective weather from 2008 to June 2010 when Henan was in the situation of Northeast vortex and the northwest airflow at the back of vortex trough,also analyze the synoptic features of the three strong storm events which resulted in hazard,and induce the element configuration of three dimensional weather system and forecast starting points for the three strong storm events.The results show that the fact with the following elements such as SI and LI are both negative values,K≥20 ℃,△θse850-500≥5 ℃,CAPE≥1500 J·kg-1,Sweat index ≥180,vertical wind shear from 0 to 6 km ≥15 m·s-1 and PW≥2 cm can be taken for reference index for disastrous severe convective weather.And the fact with the following elements such as SI is positive value,LI≥-1.5 ℃,K≤24 ℃,△θse850-500≤-4.3 ℃,CAPE≤150 J·kg-1 and is far less than CIN（revised CAPE at 14：00 is less than 500 J·kg-1）,vertical wind shear from 0 to 6 km ≤12 m·s-1 and PW≤1.5 cm can be regarded as reference index for non-convective weather.Except the facts described above,general thunderstorm weathers could be happened.In the situation of Northeast vortex and the back of trough,the thermal instability conditions causing severe convective weather in Henan are the dry and cold air in the mid-and-upper level,a significant cooling zone in 24 hours（or cold trough,or cold advection）,warm air in the low level,20 ℃ in temperature at 850 hPa（or a low-level jet or a significant streamline passing through the warm ridge）.The triggering conditions of air uplifting are zonal trough,shear and dry line in the middle level,convergence line and dry line etc.in ground layer.The water vapor conditions causing severe convective weather in Henan are that specific humidity ≥7 J·kg-1 at 850 hPa and dew point temperature is above 16 ℃ in the ground layer.The conditions on vertical wind shear are northwesterly upper-level jet,southerly wind in the lower-level and easterly wind in ground layer.