Black carbon aerosol trend in urban regions of China during 2005-2022 using MERRA-2 and CAMS reanalysis

High atmospheric black carbon (BC) levels due to human activities pose a severe air pollution issue in China, especially in urban agglomerations. In this talk, we analyzed the trends of black carbon-aerosol optical depth (BC_AOD) from Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) and Copernicus Atmosphere Monitoring Service (CAMS) from 2005 to 2022.  Four densely populated and highly polluted urban regions (Beijing-Tianjin-Hebei [BTH], Sichuan Basin [SCB], Yangtze River Delta [YRD], and Pearl River Delta [PRD]) were selected for the analysis. BC_AOD from MERRA-2 data showed significant negative trends over the four urban regions during the years 2005-2022, with rates of -0.0007, -0.0008, -0.0007, and -0.0006 yr^-1 in BTH, YRD, SCB, and PRD, respectively. Similar significant BC_AOD trends from CAMS were also observed in the urban selected regions with rates of -0.0005, -0.0006, -0.0009, -0.0006 yr^-1 in BTH, YRD, SCB, and PRD, respectively. The decreasing trend in BC_AOD could be mainly attributed to the air pollution policies implemented by the Chinese government.