Influenced by strong winds associated with a southeastward-moving Mongolian cyclone,a severe transmission line galloping occurred in Baiyin City,Gansu Province,on 14 April 2020.This caused a tripping incident of the transmission line in this region.Based on the hourly,0.5°×0.5°,ECMWF ERA5 reanalysis data,this study investigated the formation mechanisms of the Mongolian cyclone and its associated strong winds.Results from the vorticity budget indicate that the convergence-related vertical stretching and the upward transport of cyclonic vorticity governed formation of the Mongolian cyclone in this event;whereas,tilting and export of cyclonic vorticity from the central region of the cyclone mainly decelerated the cyclone’s formation.The kinetic energy(KE)budget shows that the wind associated with the Mongolian cyclone was mainly enhanced by the positive work of the pressure gradient force.Unlike some typical strong wind events in Northwest China,during this event,no significant downward momentum transportation from the upper troposphere was found.The vertical transport of KE exerted a slightly favorable effect on the KE increase around the location where the transmission line galloping trip appeared.In contrast,the horizontal transport mainly caused an export of KE from this region,which applied an overall negative effect on the wind enhancement associated with the Mongolian cyclone.
Shuanglong JinShuanglei FengXiaolin LiuBo WangZongpeng SongWei CuiCong Wang
利用常规气象观测资料和NECP再分析资料,对2013-03-09出现在山西的沙尘天气进行了分析。结果表明:1前期降水偏少、气温偏高是此次沙尘天气发生的有利背景,蒙古气旋、冷锋、副冷锋是此次沙尘天气的主要影响系统。2地面3 h变压的正的大值区和强的阵风发生区域有很好的对应关系。3500 h Pa的水平螺旋度正值对地面气旋的移动有指示意义;沙尘天气出现在500 h Pa水平螺旋度正值范围偏西、偏西南区域。4300 h Pa以上的高空急流为双急流型,急流中心风速相对较小、垂直运动相对较弱以及混合层高度相对较低是没有发生大范围沙尘暴的主要原因。
