一次阵风锋触发强对流过程雷达资料特征分析

Analysis on a Severe Convection Triggered by Gust Front in Yinchuan with Radar Data

为了进一步探索西北高原干旱区强对流触发机制,提高灾害性天气监测预警能力,以新一代天气雷达探测资料为核心,针对一次阵风锋触发的逆向传播强对流过程,进行了雷达气象学诊断分析。结果表明:(1)天气系统配置为有利的大气环境,CAPE、CIN与LFC均适合强对流的触发与发展,原生对流消亡后产生的3条阵风锋共同作用触发新生强对流。(2)新一代天气雷达能有效监测到阵风锋产生、发展、成熟、汇合、消失以及触发新生对流的过程,揭示了3条阵风锋及下击暴流的细节。(3)强反射率因子区域快速下沉且强度减退及径向速度模糊,对雷暴大风灾害的预警具有指示意义。(4)各条阵风锋的长度变化普遍经历快速增长、增幅减缓和趋于减小3个阶段,其宽度变化也具有相似的较强规律性。(5)阵风锋的运动受下垫面特别是城区较强磨擦作用影响显著,存在一定波动。阵风锋合并后,新生对流的增强需要18~30 min的成长期,为准确预警强烈天气提供了宝贵的时间提前量。(6)在天气背景分析基础上,利用雷达资料关注阵风锋初生、发展、运动情况,可望提前1 h左右发现触发新生对流征兆。通过雷达资料可准确掌握阵风锋细致变化、形成近地层急流、下击暴流,以及新生对流的发展,是监测强对流触发与预警的关键手段。

Based on the data of Yinchuan Doppler Weather Radar(CINRAD) and Automatic Weather Stations,using radar meteorological methods,diagnosis of a retro-propagating storm occurred at 19:00 July 18 2010 is conducted.The results show that:(1) The general configuration of weather systems,CAPE,CIN and LFC values are favorable for severe convection triggering and developing.Three gust fronts converged and triggered new severe convections.(2) The processes of gust fronts genesis,evolution,maturation,collision,decease and new storm-triggering are monitored by CINRAD,and the detail of 3 gust fronts and downburst is revealed.Descending of high reflectivity region and decreasing of the intensity in base reflectivity and high values in radical velocity before the downburst are of importance for disastrous gale warning.(3) All the 3 gust fronts experienced 3 stages of rapid increase,mild growth and turning decrease in length,and there is a similar trend in width.The propagations of gust fronts were affected by underlying surface especially the urban friction and result in velocity fluctuation.After gust fronts collision it took 18-30 min for the triggered convection to evolve into well mature,and so a precious leading time for accurate warning is provided.(4) Based on analysis of weather background,it can be expected to find out the clues to forecast the new convection genesis about 1 hr ahead by monitoring gust fronts changes in detail with radar data.The radar data is the key to trace the gust fronts,surface jet,downburst and triggered storms and it plays a crucial role in severe weather watching.