MEASUREMENTS AND PREDICTIONS OF SOLAR-RADIATION INCIDENT ON HORIZONTAL SURFACES AT SANTA-FE, ARGENTINA (31-DEGREES 39'S, 60-DEGREES 43'W)

Measurements and predictions of solar radiation during a period of 10 years on horizontal surfaces at Santa Fe (31 degrees 39' S, 60 degrees 43' W), Argentina, reported as average daily global radiation for eac h month, are presented. Data are compared to those obtained with a pre viously published and verified model for computing solar radiation on horizontal planes at the earth's surface for cloudless sky days. Measu rements show an important reduction of global radiation with respect t o the cloudless sky model predictions for all months of the year. Conv ersely, averaged daily diffuse solar radiation calculated with Page's formula shows a small increment with respect to the predicted diffuse solar radiation for cloudless sky conditions. When direct solar radiat ion data, calculated from global and diffuse solar radiation values, a re compared to theoretical prediction, a significant decrease is obser ved. This trend is similar to that obtained for global solar radiation . (C) 1997 Elsevier Science Ltd.