estimation of daily global solar radiation using modis data for a clear sky day (case study: northwest of iran)

Using renewable energy, particularly solar radiation is considered today as one of the most important energy resources all over the world. so that, the ratio of received solar radiation at a certain flat surface has been considered as one of important factors in crop-climate models, plant water requirement, and renewable energy systems. analyzing solar resources, satellite images are fundamental tools for deriving solar radiation values. the goal of this study is to estimate the instantaneous and daily global solar radiation using modis data in the northwest of iran (west azerbaijan and east azerbaijan province). at first, to separate water, land and snow covers from each other, ndsi index was used. then, instantaneous global solar radiation was estimated. after that, diurnal cycle of global solar radiation has been achieved using the sinusoidal model and outputs of previous step. finally, to verify the daily global solar radiation that were estimated from modis data, the results were compared to measurements of meteorological data that were obtained in tabriz and uromia stations. acquired results indicate that the rmse error is less than 41.25 w/m2. finally, comparing these results to the values that were estimated using other references, an associated error coefficient results approximately 21 w/m² were achieved.