Variability in atmospheric aerosols and effects of humidity, wind and InterTropical discontinuity over different ecological zones in Nigeria

The effects of humidity, wind, and InterTropical Discontinuity (ITD) movement on seasonal distribution of atmospheric aerosols were assessed over different ecological zones in Nigeria. Satellite-observed aerosol optical depth (AOD), humidity, wind speed, and precipitation/ITD data were used. The Moderate Resolution Imaging Spectroradiometer (MODIS) AOD time series of dataset were used. The MODIS AOD retrievals were at the wavelength of 550 nm and AOD data was re-scaled and sub-divided into seasonal and annual distributions to investigate the variations in Aerosol. Kriging spatial interpolation model was used to analyze the aerosol seasonal distribution. Correlations analysis was used to evaluate the degree of influence of humidity, wind speed, and precipitation/ITD on the seasonal distribution of aerosol over six ecological zones; Sahel, Sudan, Guinea, Rainforest, Freshwater, and Mangrove zones in Nigeria. The results show that the AOD over Nigeria is influenced by meteorological factors, but much more influenced by dust source outside the country. AOD appears much more during Harmattan season than Wet and Dry seasons; with AOD >= 0.46, with considerable concentration in Sahel ecological zone than other ecological zones. The results show a strong significant relationship between aerosol distribution and meteorological, principally humidity with R-2 >= 0.65 @ p < 0.05. The study reveals that for daily variation of AOD, wind speed, humidity and precipitation as well as spatial distribution of dust source in and outside the country are important drivers.