Long-term spatiotemporal variability of aerosol optical depth and aerosol size characteristics over the United Arab Emirates from MODIS MAIAC observations (2003–2023)

The United Arab Emirates (UAE) is characterized by an arid climate, frequent dust outbreaks, and rapid urban and industrial development, all of which influence atmospheric aerosol levels and their spatial and temporal variability. This study examines the spatiotemporal variability of aerosol optical depth (AOD) and aerosol size characteristics over the UAE from 2003 to 2023 using the MODIS MAIAC MCD19A2 product. Daily AOD at 550 nm (1 km spatial resolution) was aggregated to monthly, seasonal, and annual scales, while aerosol size characteristics were inferred using the Ångström exponent (AE) derived from AOD at 470 nm and 550 nm. The analysis reveals persistent regional differences, with higher AOD over coastal urban areas and lower values over inland desert and mountainous regions, reflecting the combined influence of natural dust activity, coastal circulation patterns, sea-salt aerosols, and anthropogenic emissions. Seasonally, summer is characterized by higher AOD and coarse-mode aerosol dominance associated with intensified dust activity, whereas winter and spring show a relatively greater contribution from fine-mode aerosols, particularly in urban regions. This two-decade, national-scale synthesis of AOD and AE variability provides insight into atmospheric aerosol characteristics in a dust-dominated and rapidly urbanizing environment and supports regional atmospheric modeling and air-quality assessment over the UAE.