The Impact of Changing Policies on Aerosol Pollution in China from 2000 to 2022

China has implemented a series of air pollution policies and measures to address its severe air pollution problem, particularly in relation to particulate aerosols. However, the temporal effectiveness of these policies remains unclear. This study investigates the impact of policy changes on aerosol pollution across China's seven major geographical regions from 2000 to 2022. The period is divided into four stages: 2000–2007, 2008–2014, 2015–2017, and 2018–2022. Using CALIPSO, MERRA2, and AERONET data, the study analyzes changes in the aerosol optical depth (AOD), an important indicator of aerosol loading, and the vertical distribution of aerosol types in the seven regions, as well as the long-range transport of aerosols at five sites during each stage. The results show that China's annual average AOD increased from 2000 to 2007, a period that was characterized by minimal air pollution restrictions and a focus on economic development. From 2008 to 2013, the increasing trend of the AOD was curbed due to the implementation of air pollution policies, resulting in relatively stable changes. From 2014 to 2017, the AOD exhibited a significant downward trend under the influence of the "Air Pollution Prevention and Control Action Plan." From 2018 to 2022, the AOD remained relatively stable. These results suggest that more stringent air pollution policies are needed to continue improving particulate aerosol pollution.