Evaluation of the NUV forecast performance against ground-based measurements in southern South America

Abstract

Abstract: Abstract. Reliable UV Index (UVI) forecast is a relevant tool to inform the population about the potential health risks of sun exposure in a specific temporal horizon. In this work, the 1-day local-noon Near-Real-Time UV index forecast (NUV) for clear sky (NUV/CLEAR) and for all-sky condition (NUV/CLOUD) is evaluated against ground-based measurements in six sites of the Argentine solar radiation network Saver-Net, covering the latitudinal range from ~30ºS to ~52°S. NUV/CLEAR is calculated using GOME-2 assimilated total ozone (ATO) as the only forecasted dynamic input, while all other atmospheric parameters and surface albedo are taken from climatology. NUV/CLOUD incorporates clouds to NUV/CLEAR using the ECMWF cloud cover fraction forecast as input. NUV/CLEAR presents an excellent correspondence with respect to ground-based observations, with low values of RMSE and MAE and high correlation with coefficient of determination above 0.99. As expected, the correspondence decreases when cloudiness is included, although NUV/CLOUD still shows a reasonable agreement.