Solar Radiation Mapping from NOAA AVHRR Data in Catalonia, Spain

Abstract

A statistical model is presented for the determination of hourly global solar radiation from the National Oceanic and Atmospheric Administration advanced very high resolution radiometer (NOAA AVHRR) satellite data, which provide wide coverage together with adequate spatial resolution (around 1.1 km at the nadir). The process is divided into three steps. The first step consists of a cloud detection procedure. The second step determines the cloud index for each point on the satellite image, which is then used for the third step, which is the application of the global solar radiation statistical model. The coefficients for the model are determined by regression from the data obtained from 11 global surface solar radiation measurement stations (pyranometers). Once the coefficients have been determined, a surface interpolation is performed to obtain the entire coefficient field for the area under study, with the objective of applying the model. The estimates obtained from the model were compared with data from another 10 ground radiation measurement stations in Catalonia, Spain. This model was tested for the 11 consecutive months beginning in February of 1998, with an excellent correlation being obtained between the estimate provided by the model and the data from the measurement stations, which resulted in a coefficient of determination of greater than 0.98 in all cases, together with an rmse of between 9.6% and 15.8% and a bias that varied from 9.5% to 1.3%. In southern Catalonia, satellite-estimated and surface-interpolated hourly global solar radiation were of equal quality (rmse of about 3%?15%). In northern Catalonia, where the stations are more sparse, the satellite-estimated values were more accurate (rmse of 7%) than those obtained from interpolation of surface station data (rmse of 11%?16%).