Abstract:

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.

Key words: dust, transmission, continuous, reverse temperature, Hexi Corridor