Characterization of aerosol loading in urban and suburban locations: Impact on atmospheric extinction

Abstract The study of atmospheric aerosols remains a very strong factor in the understanding of the Earth’s climate and predicting the air quality within any given environment. In view of this, analysis of aerosol characteristics measured using AERONET sun photometer, MODIS, Cloud-Aerosol Lidar with Orthogonal Polarization, AIRS and TOMS/OMI sensors, over six distinctly different environments in Nigeria for a period of 10 years was carried out. The results revealed significant regional and temporal variation. It showed that different aerosol types impact differently on atmospheric extinction properties. The result further revealed that aerosol loading peaks in the south and middle belt regions during the dry season (November–March), while the reverse was the case in the north during the rainy season (April–October). It was found out that coarse aerosols prevail all year round within these regions, with the rate of occurrence varying with season. The range of the ratio of coarse-to-fine aerosol was found to be as high as 19:1 during the rainy season in Sokoto and Maiduguri, and 3:1 during the dry season. In Abuja and Ilorin, it ranged from 13:1 to 2:1 in both seasons. The atmospheric extinction values plotted against relative humidity (RH) showed that extinction grows at very low RH of about 45% in a less anthropogenic polluted environment (north), while a RH of 60% and above is required for growth to take place in a more polluted environment in the south. This implies that the use of rain water for drinking and other domestic purposes should be done with caution.