Single Scattering Albedo derived from Aerosol Optical Thickness Measurement at Ilorin

Abstract

The seasonal variation of Single Scattering Albedo (SSA) derived from the monthly variations in the Aerosol Optical Thickness (AOT) values obtained from the CIMEL sun photometer in Ilorin (lat. 8⁰32^’N; long. 4⁰34^’E) is studied. Single Scattering Albedo for the site was found to range from 0.20 to 0.89 for the period under consideration - January 2003 to December 2004. For the Rain-Harmattan transition months (October and November), the SSA for the month of October was found to range approximately from 0.55 to 0.89. For the month of November, SSA was found to range approximately from 0.25 to 0.54. For the Harmattan months (December and January) and the Rainy months (April, August and September), the SSA was found to range from approximately 0.18 to 0.45. Whereas the AOT for the Harmattan months increased that of the Rainy months was decreasing for most of the months. The average monthly SSA in the Harmattan- Rain transition months (February and March) was found to range approximately from 0.20 to 0.38, depicting an increase in the Aerosol Optical Thickness at this period. These ranges show that the effect of aerosols on the direct radiation of electromagnetic waves is not negligible at the site. Therefore, this could be considered significant to atmosphere at the project site (Ilorin) by characterising it as an absorptive atmosphere.