Detection by Space-Borne and Ground-Based Lidar Observations of Air Pollution on the Example of the Hefei Area

Severe air pollution is a serious threat to public health in the Yangtze River Delta region, where high concentrations of particulate matter are often observed in winter. In the present study, a serious aerosol pollution incident in the western Yangtze River Delta, China, was investigated by using joint inversion of CALIPSO and ground-based lidar in Hefei during 17-22 January, 2019. The data of the past two years were used in this study, and four typical weather cases were selected for comparative verification-namely, fi ne weather (less cloud, good air); cloudy weather (good air, no haze); moderate pollution weather (moderate haze, no cloud); and severe pollution weather (heavy haze, cloud). The vertical profile of aerosol backscatter as the satellite passed through Hefei city was given by the data of the CALIPSO satellite-borne lidar, CALIOP, which was compared with the vertical distribution of the range-corrected signal of ground-based lidar. Combined with analysis of meteorological data, the results showed that satellite-ground lidar can be used to observe the effect of aerosol changes on weather effectively. Subsequent experiments observed and tracked severely polluted weather event, and the data on the aerosol boundary layer was obtained which was a severe trans-boundary air pollution. The serious pollution period occurred from 22:00 to 04:00 on January 19 to 20, 2019, when the aerosol boundary layer was at its lowest (less than 0.5 km) and the boundary layer height ranged from 0.5 km to 2.2 km in other periods. Then, based on analysis of near-surface data, the changes in the boundary layer during the pollution process and the possible causes of these changes were analyzed. It was concluded that, during the pollution process, the height of the aerosol boundary layer in the Hefei area showed an obvious negative correlation with the concentration of PM2.5. Finally, HYSPLIT results showed that the source of pollution weather was mainly aerosol particles blown from the north. The results of this study provide a basis for satellite- and ground-based lidar joint observation under different weather types, as well as help in the study of urban weather change and pollution prevention.