City-level variations in aerosol optical properties and aerosol type identification derived from long-term MODIS/Aqua observations in the Sichuan Basin, China

In recent decades, the Sichuan Basin (SCB) has suffered from severe aerosol pollution. Based on long-term (2003–2018) optical properties dataset derived Moderate Resolution Imaging Spectroradiometer (MODIS), this study investigated spatial distribution and interannual variation of depth (AOD) fine-mode fraction (FMF) as well type at city-level in SCB. The AOD exhibited a decreasing trend centre SCB to surrounding areas with high approximately 1.0. FMF value was 0.9 southern areas. frequency occurrence < 0.2 30%–40%. negative −0.03/year showed significant positive 0.01–0.02/year. proportion continental background aerosols higher BB/UI (biomass burning/urban-industrial) central urban area increased significantly 50%. Mix were mainly distributed north, accounting for 35%–45%. A large dust (30%–35%) noted east results are great scientific significance analysis extinction city level China. • decreased center surrounding, while changed opposite decrease 0.4, 0.7 during 2003 2018 Identification based data