Determination of Input Variables to Estimate Solar Radiation Using Entropy Theory and Principal Component Analysis

Document Type : Research Paper


1 Irrigation & Reclamation Engrg. Dept. University of Tehran Karaj, Iran.

2 Assistant Prof., Irrigation & Reclamation Engrg. Dept. University of Tehran Karaj, Iran. Tel/Fax:+98-263-2241119

3 Assistant professor, Soil and Water Department, Faculty of Agriculture, Shahrood University of Technology, Shahrood, Iran


Solar radiation arriving to the land surface is one of the major variables that is used in projects and hydrological, agricultural, meteorological and climatic models. In this study, the functionality of the principal component analysis (PCA) and the entropy theory (EN) for determination  of inputs to multilevel perceptron artificial neural network (MLP), artificial neural network, radial basis function (RBF), support vector machine (SVM)and genetic programming (GEP), was investigated for estimation of solar radiation at two stations (Kerman and Mashhad) during 1984-2005 and 1980-2004 periods, respectively. The average temperature, mean water deficit pressure, minimum temperature, maximum temperature, sunshine, relative humidity, dew point temperature, hourly vapor pressure, horizontal visibility and water content were selected as inputs of pre-processing methods. The obtained results  in Kerman station showed that the ENT-MLP model with RMSE=38.36 (Mj /m2) and R2 = 0.93 have had the best performance. Also in Mashhad station, PCA-MLP model with RMSE=79.75 (Mj / m2) and R2 = 0.77 had the best performance. In general, the both pre-processing  principal component analysis and entropy theory were recognized  as the proper methods for determination  of estimating models input to estimate  solar radiation.


Main Subjects

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