西北干旱区荒漠戈壁两次极端沙尘事件的对比研究

A comparative study of two extreme dust events in the deserts and gobi regions in the arid regions of northwest China

为深入理解极端沙尘暴事件的演变过程和驱动因子,结合多源卫星遥感及再分析数据,挑选2007年3月31日(“3·31”事件)和2021年3月14日(“3·14”事件)爆发于西北干旱区荒漠戈壁的两次沙尘暴事件,对比分析了其时空演变、高低空环流配置、近地面气象要素的变化。结果表明:(1)两次极端事件分别爆发于塔克拉玛干沙漠及戈壁荒漠,均受高低层天气系统影响。其中,“3·31”事件受地面冷锋和高空脊控制,脊前西北冷空气与地面冷锋引起的垂直运动配合,将沙尘往下游输送;而“3·14”事件则受蒙古气旋和高空槽影响,气旋后的偏北风和气旋引发的垂直运动将沙尘卷起至高层大气,并通过槽后西北风将其往下游输送;(2)两次极端沙尘事件均有持续时间长的特点,区别在于“3·31”事件主要受高压脊、均压场和周边地形影响,大气层结稳定,沙尘不易沉降和输送,而“3·14”事件则因中国北部持续性高压导致的偏南风和偏东风阻止了沙尘向下游扩散;(3)两次极端沙尘事件爆发前,塔克拉玛干和戈壁荒漠均出现了高温、降水减少及土壤水分枯竭现象,即强风和干燥土壤。为极端沙尘事件的爆发创造了有利的动力条件和物质基础。

In order to deeply understand the evolution and driving factors of extreme dust events,two dust storm events that erupted in the deserts and gobi regions in the arid regions of northwest China on 31 March 2007(“3·31”dust event)and 14 March 2021(“3·14”dust event)were selected,and their temporal and spatial evolution,high and low altitude circulation configuration,and changes in nearsurface meteorological elements were compared and analyzed based on multi-source satellite remote sensing and reanalysis data.The results are as follows:(1)Both extreme events occurred in the Taklimakan Desert and the Gobi Desert,respectively,and they were influ⁃enced by upper-and-lower weather systems.The“3·31”dust event was influenced by a surface cold front and a ridge at high altitude.The northwesterly winds in front of the ridge,in cooperation with the vertical motion caused by the cold front,transported dust down⁃stream.The“3·14”dust event,on the other hand,was influenced by a Mongolian cyclone and an upper-air trough.The northwesterly winds following the cyclone,along with the vertical motion induced by the cyclone,swept up dust and transported it downstream through the northwesterly winds following the trough.(2)Both extreme dust events exhibited prolonged durations.The“3·31”dust event was influenced by the high-pressure ridge,a sea level pressure field with little variation and the surrounding topography.This configuration resulted in a stable atmosphere,preventing the deposition and transport of dust.Different from the event above,the“3·14”dust event was caused by the persistent high pressure over northern China,which led to southerly and easterly winds that pre⁃vented dust spreading downstream.(3)Before occurrence of the extreme dust events,both the Taklimakan Desert and Gobi Desert expe⁃rienced high temperature,less precipitation,and depleted soil moisture,which formed favorable dynamic conditions and material foun⁃dations,such as strong winds and dry soils,for the outbreak of the two dust events.