INVESTIGATION OF SPATIAL AND TEMORAL VARIATIONS OF AEROSOL OPTICAL DEPTH DISTRIBUTION OVER WEST AFRICAN SUB - REGION USING VIIRS SETLITTE DATA

Abstract

West Africa has experienced rapid urbanization, economic growth, population and industrialization and no serious attention paid about aerosol emissions in the past decade. Thus, understanding the spatial and temporal variation of aerosol optical depth (AOD) are urgently needed to evaluate the effectiveness of aerosol control activities. Based on Visible Infrared Imaging Radiometer Suite (VIIRS) Satellite, the AOD was retrieved over West Africa from 2012-2024. The Monthly data was utilized for the analysis. The ground based AOD from AERONET at 550nm wavelength was interpolated for inter-comparison with VIIRS Satellite AOD data over the study period. Statistical parameters like mean, maximum, minimum and standard deviation were calculated. The result shows that, the Monthly average mean AOD value in Nigeria ranges from 0.25-0.84 while that of Benin ranges from 0.35-0.91 and Niger ranges from 0.24-0.84. The annual average AOD in Nigeria and Niger varied between 0.41-0.55 while in Benin varied between 0.44-0.58. In terms of season, Nigeria has the highest mean AOD value in spring (0.66) and lowest in winter (0.37), Niger has the highest mean AOD value in summer (0.74) and lowest in winter (0.26) and Benin has the highest mean AOD value in spring (0.70) and lowest in autumn (0.39). In addition, the AOD fluctuates greatly in 2015 and 2022 in Nigeria with highest standard deviation (0.54 & 0.47) respectively while the AOD fluctuates in 2016 and 2015 with the highest standard deviation (0.55 & 0.45) in Niger and Benin respectively. The distribution of AOD is not the same in all seasons and the temporal variation shows an upward trend in some years due to increase of human activities in some regions.

KEYWORDS; AOD; VIIRs; AERONET; Spatial; Temporal