Reconstruction of global solar radiation time series from 1933 to 2013 at the Izaña Atmospheric Observatory [Discussion paper]

This paper presents the reconstruction of the 80-year time series of daily global solar radiation (GSR) at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (The Canary Islands, Spain). For this purpose, we combine GSR estimates from sunshine duration (SD) data using the Ångström–Prescott method over the 1933/1991 period, and GSR observations directly performed by pyranometers between 1992 and 2013. Since GSR measurements have been used as a reference, a strict quality control has been applied based on principles of physical limits and comparison with LibRadtran model. By comparing with high quality GSR measurements, the precision and consistency over time of GSR estimations from SD data have been successfully documented. We obtain an overall root mean square error (RMSE) of 9.2% and an agreement between the variances of GSR estimations and GSR measurements within 92%. Nonetheless, this agreement significantly increases when the GSR estimation is done considering different daily fractions of clear sky (FCS).Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) and from the “Fondo Europeo de Desarrollo Regional” (FEDER) for projects CGL2011-23413, CGL2012-33576 and CGL2012-37505 is acknowledged