“3·15”北方强沙尘暴天气成因分析

Cause Analysis on Severe Dust Storm in Northern China on 15 March 2021

利用常规气象观测资料、风云4A卫星资料、植被覆盖资料及NCEP FNL再分析资料等,分析2021年3月14—18日席卷我国北方的大范围强沙尘暴天气的形成机制、传输特征以及影响因素等。结果表明:(1)前期干旱少雨、气温偏高及对应的北方大部植被覆盖度偏低,为强沙尘天气的发生提供了很好的沙源条件。(2)此次沙尘天气是在蒙古气旋强烈发展及其后部冷高压共同作用下发生的。(3)沙尘过程分两个阶段:第一阶段由地面冷锋后部的大风过境造成,集中发生在华北、东北等地;第二阶段受前期没有消散的高空沙尘南压扩散及沙尘回流造成,集中发生在西北地区。(4)对水平螺旋度、混合层高度以及垂直速度等物理量的分析表明,我国大部分地区的起沙条件不足,沙尘天气主要受上游沙尘输送影响。我国东部沙尘主要由蒙古国南部区域起沙贡献;而西北地区沙尘主要由蒙古国及其自身产生的沙尘贡献。

Based on conventional meteorological observation data,FY-4A satellite data,vegetation cover data and reanalysis data,the formation mechanism,transmission characteristics and influencing factors of a large-scale severe dust storm occurring from March 14 to 18,2021 in northern China were analyzed.The results are as follows:(1)Drought,high temperature,less rainfall and low vegetation coverage in the earlier period in most parts of northern China provided a good sand source condition for occurrence of the strong sand dust storm weather.(2)The dust weather was caused by the strong development of Mongolia cyclone and the combined action of cold high pressure behind it.(3)The dust weather process was divided into two stages.At the first stage it was caused by the strong winds passing behind the ground cold front,which mainly occurred in North China and Northeast China.At the second stage it was caused by the southward diffusion of high-altitude dust that did not dissipate at the early stage and the backflow of east wind,which mainly occurred in Northwestern China.(4)The analysis of physical quantities such as horizontal helicity,the mixing layer height and vertical velocity showed that the dust emission conditions were insufficient in most areas of China,so the sand dust weather was mainly affected by the upstream sand dust transportation.For the eastern region of China,the contribution of dust storm was mainly from the southern part of Mongolia.While in Northwest China it was mainly contributed by Mongolia and its own dust.