Department of Physics, The Federal University of Technology, Akure, Nigeria
Ogolo, E.O., Department of Physics, The Federal University of Technology, Akure, Nigeria
The performance of both temperature and sunshine dependent models were evaluated for different selected tropical sites, which are situated across four different climatic zones, viz. Sahelian, Guinea Savannah, Midland and Coastal area in Nigeria. The regression constants were obtained for the first, second and third order Angstrom type [Garcia J V, Principios F'isicos de la Climatolog'ia. Ediciones UNALM (Universidad Nacional Agraria La Molina: Lima, Peru), 1994; Hargreaves G & Samani Z, Estimating potential evapotranspiration, J Irrigat Drainage Eng (USA), 108 (1982) pp 225-230] models for all the stations using the method of regression analysis. Model evaluation performance analyses were carried out to determine which model is more suitable for a given climatic condition. The results indicated that the third order Angstrom type correlations do not improve the accuracy of estimation of global radiation. In addition, the results also revealed that temperature and sunshine hour dependent models are more suitable for the simulation of global radiation in the Sahelian and Guinea Savannah climatic condition, respectively. All the models exhibited the tendency to perform suitably well in the Midland and Coastal areas. On the seasonal consideration, the sunshine hour dependent models were found more suitable for the estimation of solar global radiation across all the varying climatic conditions during the dry season. However, all the models were found suitable during the wet season except for the Sahelian where only the temperature dependent models have been found exclusively suitable.
