Firouz Mojarrad - Ph.D. of Climatology, Associate Professor, Geography Dept., Razi Univ., Kermanshah, Iran
Amanollah Fathnia - Ph.D. of Climatology, Assistant Professor, Geography Dept., Razi Univ., Kermanshah, Iran
Saeed Rajaee - Ph.D. Candidate of Climatology, Geography Dept., Razi Univ., Kermanshah, Iran

Solar radiation is the most important meteorological element which affects all climatological and biological processes such as evaporation and transpiration, snowmelt and plant growth directly and indirectly. Various planning in agriculture, hydrology, architecture and energy largely depend on the correct estimation of the amount of solar radiation. One of the most accurate methods in measuring solar radiation is using pyranometer which its usage is still limited in many parts due to the lack of facilities. Consequently, the researchers are trying more to estimate the radiation, instead of directly measuring it. Most of the previous studies have used Angstrom model, having the values of sunshine hours as its input, or regression equations through considering the climatic factors and elements affecting the radiation, to estimate the solar radiation. The aim of this study is to estimate and evaluate the spatial-temporal changes of receiving solar radiation in Kermanshah Province by using the Bird and Hulstrom model.Research Methodology In this study, optimized Bird and Hulstrom model is used to estimate incoming solar radiation in Kermanshah Province by using the daily data from synoptic weather stations of the province between the years 1990- 2009. For this purpose, the amounts of incoming solar radiation on a daily basis were estimated considering local (altitude, latitude and longitude) and climatic (Humidity, temperature, pressure, length of day, sunshine hours, solar angle, sky albedo, absorption by aerosols, ground albedo, air mass, absorption by ozone, and Rayleigh distribution) characteristics. Bird and Hulstrom presented the equation (1) for estimating solar radiation concerning the effect of climatic

Estimating, Recieving Solar Radiation, Kermanshah Province, Spatial Changes, Bird and Hulstrom Model