Impacts of Anthropogenic Emissions and Open Biomass Burning in South Asia and Southeast Asia on Air Quality and Meteorology Over Southern China

The emissions from South Asia and Southeast Asia significantly impact air quality and meteorological conditions in China. However, the individual or joint contributions of anthropogenic emissions and/or biomass burning from outside China to surface particulate matter with aerodynamic diameters less than 2.5 mu m (PM2.5) and aerosol optical depth (AOD) over southern China have not been fully investigated. Here, five experiments were designed to investigate the impacts of these emissions in January (winter), March (pre-monsoon), and October (post-monsoon) for 2017. Aerosols from South Asia and Southeast Asia contributed less to southern China during winter and post-monsoon seasons, whereas the wind patterns and emission intensity during the pre-monsoon season were conducive to the transport of aerosols. During pre-monsoon season, the total emissions contributed approximately 5.0 mu g m-3 to surface PM2.5 in Xizang Province. Biomass burning in Southeast Asia increased PM2.5 in Yunnan Province by 37.9 mu g m-3, while anthropogenic emissions increased it by 8.9 mu g m-3. Transboundary aerosols can be transported to Xizang Province and Yunnan Province, primarily influencing PM2.5 below 2 km height. It mainly affected PM2.5 levels above the planetary boundary layer over southeast China. Aerosols from outside China can account for 79.5% and 54.8% AOD in Yunnan Province and southeast China, respectively. These aerosols reduced surface incident solar radiation by approximately 6%, leading to decreases in air temperature, wind speed, and boundary layer height. The findings are only applicable to the pre-monsoon season. Air pollution in South Asia and Southeast Asia is closely related to anthropogenic emissions and biomass burning. Under the influence of prevailing winds, these emissions can affect air quality over southern China during different seasons. This study combines ground observations, satellite data, and chemical transport models to investigate the impacts of anthropogenic emissions and/or biomass burning from South Asia and Southeast Asia on air quality and meteorological conditions over southern China in January, March, and October for 2017. Transportation from South Asia and Southeast Asia account for up to 50% PM2.5 concentrations over Xizang Province in China Aerosols transported from South Asia and Southeast Asia can impact PM2.5 at heights up to 6 km over southern China in pre-monsoon season Impacts on the surface solar radiation, air temperature, relative humidity, wind speed and planetary boundary layer height are quantified