Cloud cover and UV index estimates in Chile from satellite-derived and ground-based data

Clear sky ground UV index values for Santiago de Chile have been estimated for years 1979-2011 by means of an empirical reconstruction model based on data recorded by a multichannel radiometer. It allowed computing a ground-based CMF for years 1996-2011 and comparing it with satellite data. Results show that OMI CMF based on gridded cell LER data introduces significant differences with respect to equivalent TOMS CMF. On the contrary, the use of overpass LER data allows to evaluate changes in cloudiness and, by using the model, reconstructing the actual UV index. Nevertheless, LER CMF overestimates actual cloud cover conditions in winter. The trend in reconstructed satellite (ground) based UV index during summer months is + 3.3 ± 0.9% (+ 11.9 ± 2.5%)/decade for years 1979-2011 (1997-2011). Further comparisons concerning the Total Cloud Fraction product of Modern-Era Retrospective analysis for Research and Applications (MERRA) suggest that it could be used a further proxy of cloudiness for UV reconstruction models; nevertheless additional analysis is necessary.