摘要
利用多种常规和非常规资料对2014年春季和夏季发生在湖南的两次飑线过程(分别简称"3. 28"飑线和"7. 18"飑线)进行对比分析。结果表明:两次过程均发生在大气层结极不稳定条件下,中低层有明显的水汽输送,具有一定的上干下湿层结特征,飑线在低层切变线和地面辐合线附近触发,但两次过程的热动力结构及雷达回波特征存在一定差异。在物理量场上,"7. 18"飑线的热力特征更强,K指数、SI、CAPE、DCAPE等均强于"3. 28"飑线,但层结不稳定及垂直上升运动、深层垂直风切变等动力条件则前者弱于后者;雷达回波上,低仰角速度大值区、中层径向辐合,均为两次过程的预报预警着眼点,但"3. 28"飑线速度大值区范围大、出现类似"牛眼"的速度对,弓形回波特征更明显,出现多个中气旋;"3. 28"飑线的VIL和ET明显低于"7. 18"飑线,因此预警时需根据季节适当调整阈值。
Based on the conventional and unconventional data,two squall line processes on 28 March and 18 July 2014 in Hunan Province were analyzed comparatively.The results show that two squall lines happened under extremely unstable atmospheric stratification conditions,the vapor transports were obvious in middle and lower troposphere,the characteristics of atmospheric stratification with dry in upper layer and moist in lower layer were significant,and two squall lines were triggered nearby lower layer wind shear and surface convergence line.However,the thermal-dynamic structure and radar echo characteristics of two squall lines had a certain differences.The thermal features of squall line on 18 July 2014(a.k.a.‘7.18’squall line)were stronger than those of squall line on 28 March 2014(a.k.a.‘3.28’squall line),such as K index,Showalter index,convective available potential energy(CAPE)and downdraft convective available potential energy(DCAPE),etc.,but the stratification instability and dynamic conditions,such as vertical upward motions and deep layer vertical wind shear,etc.,were weaker than the later.The high value areas of velocity on low elevation and radial convergence in middle layer in radar echo figures were forecasting key points of two weather processes.Compared with‘7.18’squall line,the range of high value area of velocity for‘3.28’squall line was larger,and there were bull’s-eyes structures of radial velocity,more obvious bow echo and several mesocyclones.Moreover,the vertically integrated liquid(VIL)and echo top height(ET)of‘3.28’squall line were less than that of‘7.18’squall line,so the threshold of early warning should be adjusted properly according to different seasons.
作者
王强
唐明晖
王起唤
张骁
WANG Qiang;TANG Minghui;WANG Qihuan;ZHANG Xiao(Huaihua Meteorological Observatory of Hunan Province,Huaihua 418000,Hunan,China;Hunan Meteorological Observatory,Changsha 410007,China)
出处
《干旱气象》
2018年第5期782-793,共12页
Journal of Arid Meteorology
基金
中国气象局预报预测核心业务发展专项(CMAHX20160210)
湖南省气象局重点项目(XQKJ17A002)
预报员专项(XQKJ16C013
XQKJ18C002)
短平快项目(XQKJ18B078)共同资助
关键词
不同季节
飑线
对比分析
中气旋
different seasons
squall line
contrastive analysis
mesocyclone
