Abstract
Multiple linear regression models were developed to estimate the monthly daily Sunshine Hours using four parameters during a period of eleven years (1997 – 2007) for Calabar, Nigeria (Latitude 5o16’07.6’’N); The parameters include Relative Humidity, Maximum and Minimum temperatures, Rainfall and Wind Speed. The result of the correlations shows that the four variable correlations with the highest value of R gives the best result when considering the error term Root Mean Square Error (RMSE). The model is given as S = -11.049-6.540RF-0.534W+0.142RH+1.127T. Where RH is Relative humidity, T is the Difference in maximum and minimum temperature, RF is Rainfall, and W is wind speed. The developed model can be used in estimating Global solar radiation for Calabar and other locations with similar climatic conditions.