Daily solar radiation from NASA-POWER product: assessing its accuracy considering atmospheric transparency

ALMOROX, J.; SAYAGO S.; BOCCO, M; . OVANDO G.

INTERNATIONAL JOURNAL OF REMOTE SENSING

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2019 vol. 41 p. 897 - 910

0143-1161

Satellite remote sensing in estimating solar energy budget components at the top of the atmosphere (TOA) level and at the terrestrial level plays a very important role in various types of applications. Solar radiation data are especially problematic because of a quite generalized lack of sufficient data in quantity and quality. Satellite images allow solving the problem of continuity or lack of solar radiation data. The objective of this work was to fit daily solar radiation from NASA-POWER (National Aeronautics and Space Administration ? Prediction Of Worldwide Energy Resources), considering different intervals of atmospheric transparency index. The accuracy was assessed from the analysis of voluminous data-sets registered by meteorological ground stations, 31 in number, located in whole Spain, during the period from 2000 to 2017. Clearness index (KT) was calculated to define nine classes of cloud cover conditions. The study reveals that the degree of correlation between the satellite data and observatory data depends upon atmospheric conditions and the correlation accuracy improves for higher values of KT. The coefficients of determination (R2), considering all KT values, were between 0.85 and 0.96; particularly for clear days R2 = 0.96 and root-mean-square error equal to 1.78 MJ m−2 d−1 were obtained. Geographically, the better statistic values were located in the central region of the country. NASA-POWER shows potential to estimate solar radiation and that it is an important information resource for different applications.