2021年3月15—19日河西走廊出现了近10 a范围最广、持续时间最长的罕见强沙尘天气过程。利用MICAPS常规气象观测资料以及物理量场资料,从天气气候成因、环流形势演变、物理量诊断等方面分析了此次强沙尘天气的传输及过程持续特征。结果表明：（1） 2021年3月14日受强烈发展的蒙古低压槽影响,蒙古国南部及内蒙古中西部爆发了强沙尘暴,前期蒙古国及中国北方异常增暖是导致沙尘暴爆发的诱因之一。（2） 受高空贝加尔湖深厚低压槽后西北气流引导冷空气东移南下、高空急流动量下传、配合地面冷锋过境共同影响,蒙古国中西部高低空的沙尘粒子被输送到河西走廊,造成河西走廊15日凌晨到上午出现局地强沙尘暴和扬沙天气。（3） 强沙尘暴出现后,700 hPa、850 hPa及近地面内蒙古、华北、宁夏及陕西一带盛行偏东气流将蒙古国及内蒙古的沙尘输送到了河西走廊,造成河西走廊15日下午至19日出现浮尘天气。（4） 沙尘天气维持期间,地面冷高压移速缓慢,河西走廊位于地面冷高压后部,地面风速和湿度较小,不利于沙尘的沉降和水平扩散;河西走廊上空盛行下气沉流、逆温层深厚、大气干燥及层结稳定,不利于低层沙尘的垂直扩散和沉降,对沙尘的持续维持起到促进作用。

From March 15 to 19, 2021, a rare strong floating dust weather process with the widest range and longest duration of recent 10 years occurred in the Hexi Corridor of northwestern China. Using the meteorological information comprehensive analysis and process system conventional meteorological observation data and physical quantity field data, the transmission of the strong dust and the continuous characteristics of the weather process were investigated from a weather and climate aspect, circulation evolution, physical quantitative field diagnosis, etc. The results demonstrated that (1) strong dust storms erupted in southern Mongolia and central and western Inner Mongolia because of the strongly developed Mongolian low-pressure trough on March 14. Abnormal warming at an earlier stage in Mongolia and northern China was one of the causes of the dust storms. (2) Due to the common influence of the northwest airflow after a deep low-pressure trough on Lake Baikal guiding cold air to move east and south, high jet momentum transmission, and a ground cold front passing through, dust particles from central and western Mongolia were transported to the Hexi Corridor, causing local sandstorms and sand blowing from early morning to morning of March 15. (3) Prevailing easterly airflow of 700 hPa, 850 hPa and near-ground prevailed in Mongolia, north China, Ningxia, and Shaanxi, which delivered dust from Mongolia and Inner Mongolia to the Hexi Corridor. This caused strong dust weather in the Hexi Corridor after the emergence of strong dust storms from the afternoon of March 15 to March 19. (4) During the floating dust weather period, the northeasterly airflow from the middle-low classes of Mongolia, north China, Ningxia, and Shaanxi was continuously maintained. The ground cold high pressure moving speed was slow; the Hexi Corridor was located at the back of the cold high pressure, and ground wind speed and humidity were low, which was not conducive to dust settlement and horizontal diffusion. The dominant downward airflow, deep inversion layer flow, dry atmosphere, and layer junction stable over Hexi Corridor were not conducive to vertical diffusion and settlement of low-layer dust, which promoted the continued maintenance of floating dust.