毛乌素沙漠边缘地区春末夏初沙尘暴天气的物理量场结构

Physical Parameter Fields Structure of Dust-Storm Event in Late Spring to Early Summer in Margin Region of Mu Us Desert

沙尘暴天气是毛乌素沙漠边缘内蒙古、甘肃、宁夏、陕西等地区春末夏初特有的一种灾害性天气。应用欧洲中心再分析资料的气压场和各种物理量场,选取了5个沙尘暴个例,分析了沙尘暴时期各层气压场的特征和物理量的空间结构。结果表明:蒙古高压是影响沙尘暴的主要天气系统。在沙尘暴发生时,蒙古高压前部整层都为宽广而强劲的西北气流,从地面可伸展到200hPa附近,其物理属性是干、冷,其前部近乎于东北—西南向的区域,是锋区的密集带,也是各种物理量表现最为敏感的区域,垂直速度场为上升运动区,涡度场为正涡度区,高—低层散度差值场为正值,这些物理量都为沙尘暴的发生起到了推动和加强作用。

Dust storm event is a kind of proper harmful weather phenomenon in late spring to early summer in the margin region of Mu Us desert.Based on the ECMWF re-analysis data of fields of pressure and physical parameters and the data of five dust-storm cases,the characteristics of pressure field and spatial structure of physical parameter fields at different layers during the dust-storm event are analyzed.The results show that Mongolia anticyclone is the main synoptic system impacting dust-storm.During the dust-storm event,the front of Mongolia anticyclone is controlled by the wide strong northwest wind from surface to 200 hPa.The physical property of it is dry and cold.The front of Mongolia anticyclone is the northeast-southwest frontal surface,which is not only a dense belt but also a sensitive region of the physical parameters.In this region,the vertical velocity field is upward,the field of vorticity is positive and the field of divergence difference between 200 hPa and 850 hPa is positive.All these physical parameters have a promotive and fortified effect on the occurrence of dust-storm.