Global Solar Radiation Annual Profile, Causes and Seasonal Effects, at Ilorin, Nigeria

The data of short-wave global (total) solar radiation of 4 years (1995-1998) at Ilorin (8˚ 34′ N, 4˚ 34′ E), Nigeria was used to study the characteristic behavior of SW- global solar radiation in the tropics. To do this, its weekly average was plotted and analyzed with respect to the atmospheric constituents responsible for the behavior. On the profile obtained, two “Wells” of unequal size and depth were identified; a “hill” and a “plateau” representing the potentials of the radiation were also identified in a 52 - week year. These features were associated with seasons of the year and the radiation potentials obtainable in the region. The size of the Wells indicates the time prevalence of the atmospheric constituents causing the Wells and the length of the respective season, while the depth indicates the amount and severity of the constituents. The “Wells” and the “Plateau” constitute 3 seasons in a 52- week year. Keywords: solar radiation, radiation wells, radiation plateau, season.