Global Diurnal Variation Characteristics of Aerosol Optical Depth from 32 Years of AERONET Observations

Abstract Aerosols are ubiquitous microscopic particles in the atmosphere, and their diurnal variation characteristics reflect short‐term atmospheric changes that are crucial for climate monitoring and prediction. However, satellite, ground‐based, and reanalysis systems cannot simultaneously provide observational authenticity together with full temporal–spatial continuity. Using 32 years of hourly ground‐truth Aerosol Optical Depth (AOD) data from the global AERONET network, we identify eight representative modes of AOD diurnal variability through cluster analysis. The dominant diurnal patterns are strongly influenced by land cover and aerosol type. Comparison with MERRA‐2 reanalysis shows that only 12.7% of stations exhibit consistent all‐day diurnal AOD variability with AERONET observations. These results provide new constraints for understanding global aerosol diurnal behavior and offer guidance for satellite temporal sampling strategies and the improvement of satellite‐based AOD retrievals.