Study of Spatial Variation of Total Solar Radiation Falling on Horizontal Surface in Iraq

Due to lack of studies concerning the spatial variation of total solar radiation falling on horizontal surface in Iraq , this give an importance to perform this research. A mathematical model was found in this study to estimate global solar radiation on plane surface as a function of relative humidity, mean air temperature and sun shine ratio, the model give a high accuracy on application .
Figures concerning the spatial variation of total solar radiation were found during the winter, spring, summer and autum months by using 17 meteorological stations spread over the whole Iraq .
Mean monthly values of total solar radiation over Iraq were in the range of (2307, 6842) W.d/m during the months of the year .
Annual spatial variation of total radiation in Iraq show a gradually increase of total solar radiation from the north toward the south of Iraq.