COMPARISON OF SOLAR RADIATION FORECASTS FOR THE USA

Global radiation short time forecast of three different models (ECMWF, NDFD and GFS/WRF) have been compared. The comparison was made for a half year period (summer 2007) at three different climates in the USA. ECMWF shows the best results, followed by NDFD and GFS/WRF. Uncertainty varies strongly from place to place. The breakeven with persistence is reached after 2-3 hours. Distributions of hourly values do differ from measured values, but are quite similar to global radiation data based on satellite data.