An investigation of changes in total solar radiation received at ground level in semi-arid areas using modified data of field stations- Case study: bolometric stations in Tabriz and Kermanshah

Solar radiation is one of the most important and influential parameters in thermal balance of the atmosphere and thus it is considered to be the basis of many climatic studies. Evapotranspiration is defined by the amount of available energy for evaporation. Since energy at ground level is mostly supplied by the sun, many researchers have been interested in the influence of solar radiation on agriculture and especially irrigation sciences. Main research variables include total radiation received at ground level and the slope of radiation changes which are calculated and analyzed using data quality control and routing methods recommended by World Meteorological Organization, and measured at two different geographical points with semi-arid climate. Regarding Pearson correlation coefficient, the significance level of Kermanshah station was set at 99% and Tabriz was set at 95%. Total annual radiation and statistical period are positive related. With an increase in statistical years, annual radiation increases with an appropriate slope which shows the ascending trend of annual radiation in stations.