Introducing a new model for estimating solar radiation in arid and semi-aridregions of Iran

Estimated daily solar radiation (Rs) based on meteorological parameters measured at surface of the Earth is widely used in various fields. Due to the economic and technical limitations, measurement of this parameter is not possible in all areas. Therefore, daily solar radiation should be estimated based on mathematical models. One of the conventional methods for estimating solar radiation received at the earth surface, is using proposed site-depending models for this purpose in the world. The aim of this study is introducing a new general model to estimateRs in arid and semi-arid regions of Iran. To achieve this goal, climatic data such as daily minimum and maximum air temperatures, in the period of 1970-2010, geographical coordinates (latitude and altitude) of synoptic stations of Isfahan, Kerman, Mashhad, Tabas and Khorobiabanak were collected. Then several global common site – dependent models for Rs estimation were evaluated and, comparing their efficiencies with respect to the statistical indicators, most graceful model was introduced. To provide a general model, between the coefficients of the most profit site - dependent model and characteristics of each location (latitude and altitude) in any station, multiple linear regression relationships were created and analyzed, on the basis of the above calculations, a new general equation was derived.
Results showed that the general temperature-dependent model proposed in this study, with an ME of the 0.80, MBE of -0.01, RMSE of 6.50, and mean of 0.690 is the most profit model for estimating of daily solar radiation (Rs) in arid and semi-arid regions of Iran.