Anthropogenic and Natural Causes for the Interannual Variation of PM_2.5 in East Asia During Summer Monsoon Periods From 2008 to 2018

Abstract. There was a significant difference in near-surface PM_2.5 changes across China after the implementation of the Clean Air Action Plan in 2013. This study used the regional climate-chemistry-ecosystem coupled model, RegCM-Chem-YIBs, to investigate interannual variations in PM_2.5 across East Asia from 2008 to 2018. The drivers of PM_2.5 variability were examined from Anthropogenic and Natural perspectives. Compared to 2008, PM_2.5 showed little variation during 2009–2013 (the PreG phase). However, during 2014–2018 (the PostG phase), a substantial decline in PM_2.5 was simulated, particularly in the North China Plain (-36.76 μg/m³) and the Sichuan Basin (-33.96 μg/m³). Anthropogenic pollution emissions were the primary drivers of PM_2.5 reductions, contributing -10.39 to -3.82 μg/m³ in the PreG period and -33.86 to -8.45 μg/m³ in the PostG period. The influence of meteorological conditions on PM_2.5 during the PreG phase (-6.31 to 2.32 μg/m³) was comparable to that of anthropogenic pollutant emissions. Additionally, in the vegetation-rich region, the impact of CO₂ changes on PM_2.5 was comparable to that of anthropogenic pollutant emissions. Our study comprehensively examined the drivers of PM_2.5 concentration changes from 2008 to 2018. We highlight a significant intensification in the contribution of anthropogenic pollutant emissions and reveal that, in regions characterized by dense vegetation, changes in CO₂ concentrations exert a pronounced impact on PM_2.5 variations.