Empirical models for the correlation of global solar radiation with meteorological data for Iseyin, Nigeria

A number of multilinear regression equations were developed to predict the relationship between global solar radiations with one or more combinations of the following weather parameters: clearness index, mean of daily temperature, ratio of maximum and minimum daily temperature, relative humidity and relative sunshine duration for Iseyin Nigeria for five years (1995-1999). Using the Angstrom model as the base, other regression equations were developed by modifying Angstrom equation. The value of correlation coefficient (r) and value of Root Mean Square Error (RMSE), Mean Bias Error (MBE) and Mean Percentage Error (MPE) were determined for each equation. The equation with the highest value of r and least value of RMSE, MPE and MBE is given as: H/H-0 = 1.3467 + 0.5305 (S/S-max) - 1.567(theta) + 0.0033(RH) - 0.00806(T), where H/H-0 is the cleanness index, RH is the relative humidity, S/S-max is the relative sunshine duration, is ratio of minimum and maximum daily temperature, T is the monthly average daily temperature. The developed model can be used for estimating global solar radiation on horizontal surfaces.