Aerosol Characteristics of Dust Weather on North Slope of the Qilian Mountains

Understanding the vertical distribution characteristics of aerosols in dust weather is crucial for further discussion of aerosol-cloud interaction and its impacts on weather and climate. In response to a dust storm in Northwest China on 6 September 2023, Gansu Weather Modification Office conducts aircraft detection and operational flights on north slope of the Qilian Mountains, obtaining the vertical detection data of aerosols. The vertical distribution of aerosols in dust weather is analyzed, and causes of vertical distribution of dust aerosols, related meteorological factors and air mass sources are studied. Results show that the dust weather is formed under the combined action of the upper front area and the surface cold high pressure. Affected by the dust weather, the peak mass concentration of PM10 and PM2.5 reaches 1150 μg·m-3 and 282 μg·m-3, respectively, at Wuwei Environmental Monitoring Station on north slope of the Qilian Mountains. Under the influence of dust weather, aerosol particles across all size segment show an increase in number concentration and particle size. Most of the dust particles are 1.2-1.8 μm and 6.5-16.6 μm in size, and there is a large concentration of aerosol particle number at the height of 4000-4500 m and 3000-4000 m. In addition, compared with the average concentration of particles in the fine particle segment and the coarse particle segment, the average concentration of particles increases by 2 times and 3.5 times, respectively. The average particle size increases by 3 times and 1.5 times, respectively. After the transit of sand and dust, the spectrum width widens, and the high-value region of the number concentration shows an overhanging state. In the coarse particle segment, the distribution of aerosol particle spectra changes from bimodal to trimodal. The increase in aerosol particle number concentration is more pronounced in the coarse particle segment and the lower layer. At the altitude of 500-2000 m above the ground, aerosol particles mainly come from the Gurbantunggut Desert in Xinjiang, while at the altitude of 2000-3000 m, aerosol particles mainly come from the Badain Jaran Desert in Inner Mongolia. In addition, the vertical upward movement in the middle layer and the strong northwest wind speed in the lower layer may play an important role in the vertical and spectral distribution of aerosols. Various sources and transport layers of aerosols, along with the vertical distribution evolution of meteorological elem