PRELIMINARY INVESTIGATION OF THE ATTENUATION OF SOLAR RADATION IN THE ATMOSPHERE OVER MAKURDI, NIGERIA

The attenuation of solar radiation in the atmosphere over Makurdi (Latitude 7o 7’ N and longitude 8o 6’ E) was investigated by measurements of direct solar radiation (I) carried out using a digital sun photometer that measured in Wm- 2. The measurements were made at 9:00hrs, 12:00 hrs and 15: 00hrs daily for six months. Global solar radiation, (IG) was calculated for the six months using Gun Bellani measurements from Air Force Base, Makurdi. The diffuse component of solar radiation (ID) was evaluated and the extraterrestrial solar radiation (Io) was obtained by calculation using the equation of Duffie and Beckman (1983) and Liou (1980). The variation of attenuation with clearness index Ki was found. The attenuation in the atmosphere over Makurdi was found to be highest in the month of August with a value of 0.975 and lowest in December with a value of 0.427. There was good agreement in the pattern of variation of attenuation in Makurdi when compared with that of Ilorin that lies in the same geographic latitude.