景德镇一次雷暴回波“崩塌”现象与强风关系的分析

Analysis of Echo Characteristics of Strong Wind Caused by“Collapse”Phenomenon of a Thunderstorm Echo

为了解雷暴回波形成强风的原因,使用自动气象站数据、雷达拼图组合反射率(CR)产品、新一代天气雷达(CINRAD-SA)、雷达产品生成子程序(PUP)和景德镇TWP3型边界层风廓线雷达等资料,采用天气学、雷达气象学等方法,对2017年8月20日雷暴回波的特征进行分析,结果表明:(1)赣东北强风过程的影响系统为西太副热带高压(北部边缘),500 hPa前倾槽、湿度锋、850 hPa切变线,地面有辐合线等。(2)景德镇附近不断有对流回波新生、发展、合并,组合反射率(CR)强度达到65 dBZ,60 dBZ强回波面积增大≥100 km^(2),回波处于最强盛时刻,但没有出现大风。(3)温度锋区和湿度锋区对雷暴回波的影响主要表现在新生对流回波、回波快速发展和回波异常活跃上。(4)强风往往产生于雷暴回波最强盛至快速减弱时刻,CR回波强度60~65 dBZ减弱为55~60 dBZ,55 dBZ回波面积快速减小且分散;回波顶高(ET)从18 km降到15 km;垂直积分液体水含量(VIL)从50 kg/m^(2)降到30 kg/m^(2);这些变化在两个体扫时间内快速完成,故称为“崩塌”现象。(5)反射率因子垂直剖面RCS上,CR回波强度从60 dBZ降到55 dBZ,55 dBZ回波面积迅速减小;径向速度垂直剖面(VCS)上,强回波区由正负速度对、低层辐合、高层辐散迅速转变为负速度区;地面开始出现强风。研究结果对局地雷暴大风或强风天气的预警监测有指导意义。

In order to understand the cause of thunderstorm echo forming strong wind,the characteristics of thunderstorm echo on August 20,2017 were analyzed using the data of automatic weather station,radar composite reflectivity mosaic(CR)product,new generation weather radar(CINRAD-SA),PUP productand TWP3 boundary layer wind profile radar in Jingdezhen,etc.The results show that:(1)the influence system of the strong wind process in Northeast Jiangxi is the Western Pacific subtropical high(northern edge),500 hPa forward trough,humidity front,850 hPa shear line,conver-gence line on the ground,etc.(2)Convection echoes are constantly emerging,developing and merging near Jingdezhen.The composite reflectivity(CR)intensity reaches 65 dBZ,and the area of 60 dBZ strong echo increases≥100 km^(2).The echois at its peak,but there is no strong wind.(3)The influence of temperature front and humidity front on thunder-storm echo is mainly manifested in the newborn convection echo,the rapid development of echo and the abnormal activi-ty of echo.(4)Strong winds often occur from the time when thunderstorm echo is strongest to the time when it weakens rapidly.At this time,CR echo intensity of 60-65 dBZ weakens to 55-60 dBZ,and the echo area of 55 dBZ rapidly de-creases and disperses;Echo top height(ET)drops from 18 km to 15 km;Vertical integrated liquid water content(VIL)decreased from 50 kg/m^(2)to 30 kg/m^(2).These changes occur and disappear rapidly within the scanning time of two indi-viduals,so they are called“collapse”phenomenon.(5)On the RCS of the reflectivity factor vertical profile,the CR echo intensity decreases from 60 dBZ to 55 dBZ,and the echo area with 55 dBZ CR decreases rapidly;on the radial veloc-ity vertical cross-section(VCS),the strong echo region rapidly changes from positive and negative velocity pairs,low-level convergence and high-level divergence to negative velocity region;strong winds began to appear on the ground.The results of the study have guiding significance for the early warning and monitoring of thunderstorm or strong wind weather.