On the formation and wind enhancement mechanisms of a Mongolian cyclone that caused a transmission line galloping trip in Gansu province: 导致甘肃输电线路舞动的蒙古气旋的形成及增风机理研究

Abstract 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. 摘要 受一次向东南方向移动蒙古气旋强风的影响, 2020年4月18日甘肃省白银市的高压输电线路出现了严重的舞动, 这造成了该地区的输电线路跳闸事故.基于0.5度逐小时分辨率的ERA5再分析数据, 本文研究了这次蒙古气旋及其强风的形成机理.涡度收支的结果表明, 辐合相关的垂直伸展以及垂直运动向上的正涡度输送是本次蒙古气旋形成的主因, 而倾斜项的负涡度制造以及从气旋中心区域向外的正涡度输送在一定程度上不利于蒙古气旋的形成.动能收支的结果表明, 蒙古气旋所伴随的风场主要由于气压梯度力的做功而迅速增强.与我国西北部其它的典型强风事件不同的是在本次事件中, 未发现显著的来自于对流层高层的动量下传现象, 垂直的动能输送在本次事件中仅对强风的形成有些许的促进作用.此外, 水平风场对动能的输送作用使得蒙古气旋大风区的动能存在向外的净输出, 这对蒙古气旋强风的生成有一定的延缓作用.