VIIRS observation of aerosol type distribution and seasonal AOD variability in West African coastal regions

Abstract

Monitoring atmospheric aerosol loading is crucial for understanding air quality, environmental pollution, public health, and climate change. This study investigates the seasonal variation and aerosol types over the coastal regions of West Africa—Sierra Leone (SLE), Liberia (LBR), and Southern Côte d’Ivoire (CIV)—using the AERDB_D3_VIIRS_SNPP dataset from the Visible Infrared Imaging Radiometer Suite (VIIRS) for the period 2012–2024. Validation with ground-based AOD measurements confirmed the reliability of the satellite data. The results show higher Aerosol Optical Depth (AOD) values during spring due to increased anthropogenic emissions, with mean AODs of 0.57, 0.60, and 0.58 for CIV, LBR, and SLE, respectively. Lower values occurred in autumn (0.31, 0.28, and 0.29), corresponding to reduce bush burning and human activity. Monthly maxima were observed in February, while minima occurred in September. Inter-annual analysis revealed a rising AOD trend influenced by anthropogenic aerosols, Saharan dust transport, and sea salt intrusion. Aerosol typing based on AOD and Angstrom Exponent relationships identified biomass burning (BB), sea salt (SS), Saharan dust (SD), and vehicular emissions (VE) as dominant types. The findings underscore the strong influence of both natural and anthropogenic sources on aerosol loading, providing valuable insights into climate–aerosol interactions in coastal West Africa.