Evolution of aerosol optical depth over China in 2010–2024: increasing importance of meteorological influences

Abstract. Time series of MODIS/MAIAC C6.1 aerosol optical depth (AOD) and model-simulated AOD over China were used to determine contributions of meteorological and anthropogenic effects on aerosol variations on monthly and interannual scales. The study covered the period January 2010–September 2024 with the main focus on five representative areas: NCP, YRD, PRD, HNB and SCB. The time series confirm that emission reduction policy has resulted in the effective reduction of the AOD over China. The large increase of the AOD over the YRD during 2018–2021 shows that meteorological effects have increasingly larger influences on the aerosol load as AOD decreases. During this period, the potential decrease of the AOD over the NCP was effectively cancelled by unfavorable meteorological effects. Meteorological effects, and their variations, are different over each region. For instance, over the NCP, meteorological effects were mostly unfavorable while in contrast, over the PRD, meteorological effects were initially unfavorable but had a strong effect after 2016 when they reinforced anthropogenic effects, resulting in a substantial reduction of the AOD. In addition, the data show a strong AOD minimum in 2022, attributed to favorable anthropogenic effects, over some areas reinforced by favorable meteorological effects. Monthly mean AOD patterns were distinctly different before and after 2016, suggesting that aerosol properties changed in response to emission reduction policy. In summary, this study highlights the complex interplay between meteorological and anthropogenic factors in shaping AOD variations across China and demonstrates the increasing significance of meteorological conditions in modulating China’s AOD.