Estimating monthly solar radiation in south-central Chile

José Álvarez1*, Helena Mitasova2, and H. Lee Allen1

Solar radiation is a key component in process-based models. The amount of this energy depends on the location, time of the year, and atmospheric conditions. Several equations and models have been developed for different conditions using historical data from weather station networks or satellite measurements. However, solar radiation estimates are too local since they rely on weather stations or have a resolution that is too coarse when working with satellites. In this study, we estimated monthly global solar radiation for the south-central region of Chile using the r.sun model and validated it with observations from automatic weather stations. We analyzed the performance of global radiation results with the Hargreaves-Samani (HS) and Bristow-Campbell (BC) models. Estimates from a calibrated r.sun model accounted for 89% of the variance (r2 = 0.89) in monthly mean values for 15 locations in the research area. The model performed very well for a wide area and conditions in Chile when we compared it with the HS and BC models. Our estimates of global solar radiation using the r.sun model could be improved further calibrating ground measurements and more precise cloudiness estimates as they become available. With additional procedures, the r.sun model could be used to provide spatial estimates of daily, weekly, monthly, and yearly solar radiation.

Keywords: solar radiation, r.sun model.
1North Carolina State University, Department of Forestry and Environmental Resources, Raleigh, North Carolina, USA. *Corresponding author (jsmunoz@ncsu.edu).
2North Carolina State University, Department of Marine, Earth and Atmospheric Sciences, Raleigh, North Carolina, USA.