2016年一次南支槽引起的中-α尺度飑线天气过程分析

Analysis of a Meso-α-scale Squall Line Weather Process in 2016 Caused by Southern Branch Trough

2016年4月19日14—23时云南出现一次中-α尺度的飑线,过程以雷暴大风为主,局部伴有冰雹。利用常规气象观测资料,MICAPS地面和探空资料,FY2卫星红外、可见光、水汽、TBB等云图资料、多普勒雷达资料,对这次过程进行分析,结果表明:飑线发生前6h云南上空即已具备上干冷、下暖湿的大气不稳定层结,强的垂直风切变和充沛的水汽条件,当南支槽移过云南时槽前对流云系东侧演变成飑线云团,云团南侧有明显的出流边界——弧状云线,南支槽前的抬升气流和弧状云线的共同作用下触发此次飑线的发生。强的垂直风切变的维持、动量下传和对流云团的合并是飑线维持较长时间的主要原因。飑线在TBB梯度的大值区前侧,雷达回波呈现出弧状的形式,飑线的部分时段还显示出中层径向辐合的特征,大风主要出现在飑线后部有强的入流急流的前侧强回波带上。

A meso-α-scale squall line appeared in Yunnan at 14-23,April 19,2016. The process dominated by thunderstorms with hail was analyzed by conventional meteorological data： MICAPS ground and sounding data,FY2 satellite infrared,visible light,water vapor,TBB and other cloud data,and Doppler radar data. The results show that the squall line occurred before 6 h over Yunnan already have on the dry and warm atmosphere under the unstable stratification,strong vertical wind shear and abundant water vapor conditions. When the southern branch trough moved across the Yunnan trough the convective clouds on the eastern side of the turned into squall line clouds,the cloud line occur on the south side. The squall line triggered by southern branch trough and cloud line. The maintenance of strong vertical wind shear,Momentum transmission and merging of convective clouds are major reasons cause of the squall line for a long time. The squall line is at the front of the large value area of the TBB gradient. The radar shows the form of Bow Echo. The part of squall line also shows the MRAC,strong winds occurred at a part of squall lines which have inflow stream.