Data quality assessment and monthly stability of ground solar radiation in Galicia (NW Spain)

Routine measurements of irradiance are valuable for many research fields such as energy applications. However, ground data of solar global radiation can present questionable values. In this study, a set of check procedures was used to test the quality of solar global radiation measurements taken at 75 observatories in Galicia (NW Spain) during 2005–2007. In this short period, the number of radiometric stations in the region increased from 30 to 75. A simple reliability index was defined to characterize the ability of a given station to supply quality data during the study period. Most of the data fulfilled the control procedures; moreover, some data could be recalculated from daily and 10-min records. However, data from certain stations were removed. Then, the stability of the solar radiation was assessed through statistical analyses. Monthly global radiation followed normal distributions in 35 out of 36 months, December 2007 being the only exception. Irradiation was more stable in summer and winter months than in spring and autumn. Records from certain stations showed a high correlation. Solar radiation from two station networks taken from the dataset was interpolated in order to exemplify the improvement obtained from using a higher quality dataset when mapping this variable. The obtained database can be used in further research. 2011 Elsevier Ltd. All rights reserved.