一次高层东风波背景下风雹过程成因分析

Cause Analysis of a Wind and Hail Process Induced by High-level Easterly Wave

2015年7月29日浙江出现大范围冰雹和雷雨大风,影响范围、强度远超各级台站预判。利用地面气象站、区域自动站、FY-2G红外云图、多普勒雷达产品、NCEP(1°×1°)分析资料,对该过程进行综合分析。结果表明:1)由多单体风暴组成、位于高层东风波槽前的中尺度对流复合体是本次大范围强对流天气过程的直接制造者。2)中等偏弱的垂直风切变、上干下湿的水汽垂直分布及东风波西进叠加于低层暖区之上形成强不稳定层结是多单体风暴发生发展的有利环境背景。3)热带东风急流和高层东风波形成的辐散抽吸、近地面非绝热加热升温、地形抬升和边界层辐合线为对流发生发展提供有利动力抬升和对流触发条件。4)逆风区的出现、发展和控制与雹暴单体强度的发展、维持和减弱阶段有很好的对应关系。脉冲风暴单体中层径向气流辐合与核心反射率因子的下降对地面大风预报存在2个体扫的时间提前量。5)东风波系统以动能转换的方式为本次对流天气过程中的中尺度系统发展提供动能补给。6)加强500 h Pa以上中高层东向系统的监测和雷达产品短临实时监测,可提高此类对流过程预报的时间提前量。

A large scale hail and thunder wind process occurred in Zhejiang province on July 29th 2015. The extension and intensity are far larger than the forecast. Based on surface and automatic weather stations data, FY 2G infrared cloud image, Doppler radar data and NCEP （1°×1°） reanalysis data, a comprehensive analysis of the process is conducted. Results are as follows. 1）The meso scale convective complex located in front of high level easterly wave, composed of multi cell storms is the direct manufacturer of this large scale convective weather. 2）The high level easterly wave moving upon the low level warm area, the moderate to weak ambient vertical shear , and the upper dry and lower moist vertical profile all strengthenned the instability of atmospheric stratification.3）The upper pumping induced by the tropical easterly jet and high level easterly wave, the nonadiabatic heating, the topographic uplifting and the boundary layer convergence line provide favorable uplifting and triggering conditions. 4）The appearance, development and cover of adverse wind area have a good correspondence relationship with the development, maintaining and weakening of hailstorm cell. Mid level radial convergence and the descending of reflectivity core in the pulse storm cell can indicate the gale burst 2 volume sweeps in advance. 5）The easterly wave provides kinetic energy for the meso scale system in manner of kinetic conversion. 6）Strengthening the monitoring of easterly system in middle and up level above 500 hPa and the short term and real time monitoring of radar products can improve the prediction time of such convective process.