Abstract
LiDAR and CALIPSO satellites are effective tools for detecting air pollution, and by employing PM2.5 observation data, ground-based LiDAR measurements, CALIPSO satellite data, meteorological data, and back-trajectory analysis, we analyzed the process of pollution (moderate pollution, heavy pollution, excellent weather, and dust transmission weather) in Hefei, China from 24 to 27 January 2019 and analyzed the meteorological conditions and pollutants causing heavy pollution. Observation data from the ground station showed that the concentrations of PM10 and PM2.5 increased significantly on 25 January; the maximum value of PM10 was 175 µg/m3, and the maximum value of PM2.5 was 170 µg/m3. In this study, aerosol transboundary transport was observed using a combination of ground-based LiDAR and CALIPSO satellite observations. This method showed that aerosols were distributed at a height of 3–4 km over Hefei at 12:00 on 26 January, and it was found that the aerosols came from the desert region in northwest China. Moreover, we determined its transport pathway based on the backward trajectory, and the transportation of pollutants from the surrounding important industrial cities in central and eastern China led to severe pollution after aggregating and mixing with local aerosols in Hefei in the winter. Therefore, the method proposed in this paper can effectively monitor the optical properties and transportation process of aerosols, help to explore the causes of pollution under complex conditions, and improve environmental quality.
Highlights
Aerosols are fine particles and liquid droplets suspended in the atmosphere
PM2.5 refers to particles with an equivalent diameter of less than or equal to 2.5 μm in ambient air, and PM10 refers to particles with a particle size less than 10 μm [7]
The boundary layer height was lower from 24 to 25 January; the height was approximately 1 km, the values near the ground were greater than 25 mV, and the pollutants gathered at the bottom of the troposphere
Summary
Aerosols are fine particles and liquid droplets suspended in the atmosphere. Due to their ability to reflect and scatter light, they affect the radiation and heat balance of the Earth’s atmosphere and have direct, semi direct, and indirect effects on the climate [1,2,3], which directly affect air quality. Observing the optical properties and temporal and spatial distribution of pollutants in Hefei will help to understand the pollution status and climate impact of large cities in eastern China in recent years [10]. Wu et al [17] found that the CALIPSO data performed well in classifying aerosol types; the inversion results of CALIPSO and ground-based LiDAR deviated little in the experiment. These studies only illustrated the stability of ground-based and satellite data systems from a comparative perspective and could not analyze their temporal and spatial variations combined with contaminants. Ground-based LiDAR and satellite data enabled effective remote sensing of aerosol optical properties and transport processes.
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