Using an Eppley ‘Black and White’ pyranometer fitted with a shadow band and a digital recorder/printer, hourly diffuse solar irradiance Hd falling on a horizontal surface at Ilorin, Nigeria has been measured from February to July 1993. The diffuse radiation data, after necessary correction for shadow band effect, were analyzed to obtain the diurnal and monthly variations of Hd. The highest daily total of diffuse radiation (Hdd) of value 4473±60 Wm−2 day−1 was recorded on the dust‐haze day and the lowest of value 2194±29 Wm−2 day−1 on a mostly overcast day. Similarly, the highest monthly average of daily total of diffuse radiation Hdm, of value 3237±43 Wm−2 day−1 was observed in April and the least of value 2872±34 Wm−2 day−1 in February. Also obtained are the diurnal and monthly variations of hourly values of Hd/H, where H is the corresponding hourly global irradiance measured separately by another instrument at the same location and time as Hd.

This content is only available via PDF.
You do not currently have access to this content.