Seasonal Variability of Aerosol Optical Depth and Cloud Optical Depth over Kogi East, Nigeria Using MODIS Aqua Satellite Observations (2019–2025)

Abstract

Atmospheric aerosols and clouds are important components of the climate system because of their effects on radiation, precipitation, and atmospheric processes. However, limited information is available on the combined seasonal behaviour of aerosol and cloud optical properties over Kogi East, Nigeria. This study investigated the seasonal and interannual variability of Aerosol Optical Depth (AOD) and Cloud Optical Depth (COD) over Kogi East using MODIS Aqua satellite observations from January 2019 to December 2025. Monthly AOD and COD observations were obtained through the NASA Giovanni platform and analysed using descriptive statistics, seasonal comparison, Pearson correlation, and simple linear regression. AOD ranged from 0.328 to 1.368, with a mean of 0.616 ± 0.259, while COD ranged from 1.966 to 20.088, with a mean of 8.290 ± 4.591. AOD generally exhibited higher values during the dry season, consistent with enhanced dust transport and reduced precipitation, whereas COD was generally higher during the wet season, when atmospheric moisture and convective cloud development were enhanced. Pearson correlation showed a moderate negative association between AOD and COD (r = -0.469), while the regression model (COD = 13.432 − 8.3394AOD) produced an R² of 0.2202. The results indicate that AOD and COD exhibit strong seasonal variability and that their relationship is also affected by other atmospheric processes. The study provides a satellite-based baseline for further investigation of aerosol–cloud interactions over Kogi East and the wider Guinea Savannah region of Nigeria.