垂直能量螺旋度指数及其在槽前型雷暴大风预报中的应用

摘要

A new concept of vertical energy helicity（VEH） index is proposed,and its physical meaning is explained.In order to prove its effect,by using the NCEP（1°×1°） reanalysis data and the important weather data of MICAPS,the vertical energy helicity index is applied to a thunderstorm in front of trough which took place in the north of China from July 4 to 7 in 2009.Further more,its universality is proved by using four cases taking place in the north of China in summer from 2008 to 2009.The result shows that the vertical energy helicity index can reflect the ability of unstable energy releasing from spiral ascending process and has better superiority in forecasting thunderstorm than other indexes.Generally,if the VEH index is larger than 1.4 J.m.kg-.1s-2at 14：00,a thunderstorm will happen within 3-6 h.%引入垂直能量螺旋度指数（VEH）的概念并分析其物理意义,同时采用NCEP 1°×1°再分析资料和MICAPS重要天气报文资料,将该指数应用于2009年7月4—7日华北地区一次槽前型雷暴大风过程的预报中;在此基础上,利用华北地区2008—2009年夏季4次槽前型雷暴大风个例,对该指数的普适性进行验证。结果表明,该指数反映了气块在螺旋上升过程中释放不稳定能量的能力,是诊断和预报槽前型雷暴大风的有效指数;并将该指数应用于一次华北典型槽前型雷暴大风的预报中,通过对比其它指数,证明其有效;用14时的VEH指标,预报20时前的雷暴大风天气,这种天气一般在VEH超过1.4 J.m.kg-.1s-2的3～6 h之间出现。