Estimation of Hourly Photo synthetically- Active Radiation (PAR) From Hourly Global Solar Radiation (GSR) In Jos, Nigeria

In this work, an hourly model was used in estimating the values of Photo-synthetically Active Radiation (PAR); a parameter closely related to plant growth in Jos, Nigeria (Latitude 90 57’ N, Longitude 8053’E ) and Altitude 1153m asl.) from hourly Global Solar Radiation Rs and to predict its hourly (PAR) daily seasonal trend. For this purpose, three years (2003, 2004 and 2005) data recorded using Gunn-Bellani Radiation Integrator at the weather observatory station of Geography and Planning Department of the University of Jos was used. The trend of variation of the mean hourly PAR shows that the maximum was obtained at 12.00p.m. for the raining season months of June, July and August for year 2003 are respectively 3.176 EmJ-1, 2.900 EmJ-1 and 2.960 EmJ-1 while that of the dry season months of November, December and January for the same year are respectively 3.871EmJ-1, 3.997 EmJ-1 and 3.655EmJ-1. Also, there exists seasonal variation in the average predicted value of the hourly global PAR; two maxima occurred- major at February and March and the minor at November and December. The trend of variation of hourly QP/RS (μEJ-1) for the year 2003, 2004, and 2005 with local time shows maximum values at noon for the months considered. The ratio is lower and more variable in wet season than in dry season, and is usually higher at noon.