Variation Characteristics of Photosynthetically Active Radition (Par) Over Ilorin in the Tropics

Abstract

The annual variation of photosynthetically active radiation (PAR) measured over five (5) years period (2005- 2010) at Ilorin (80 32’N, 40 34’E) was studied. The average daily and weekly PAR were obtained and plotted. The behavior of average daily PAR is similar to that obtained for the weekly average. There is a daily and weekly fluctuation in PAR throughout the year. The highest value of PAR is 33.96MJ/m2/day which occurred during the Harmattan period and minimum during the rain period with a value of 22.816MJ/m2/day. The average PAR for the Harmattan and Rain period is found to be 37.585 and 29.125MJ/m2/day respectively, while the average annual PAR is 30.050MJ/m2/day. When PAR is plotted against days of the year, the plot is described by a logarithm fit as y= -1.39ln(x) + 39.91 with a weak correlation R2 = 0.387. Also, when PAR is plotted against weeks of the year, the plot is best described by a logarithm fit as y= -1.56ln(x) + 34.74 with correlation R2 = 0.524.