Local-Scale Variability of Solar Radiation in a Mountainous Region

Abstract

Simultaneous measurements of horizontal global solar irradiance and other meteorological parameters have been taken over three years at a dense radiometric network. The network is located on a mountainous region in southeastern Spain (37°N, 3°W) covering elevations from 456 to 3398 m above mean sea level. This dataset has been used to study the spatial variability at a local scale. The great heterogeneity of the area is reflected in the great spatial variability encountered. The purpose of the study is to obtain an estimate of the small-scale solar variability of the daily, hourly, and shorter-scale solar irradiance values. Following previous results at a similar spatial scale, no mathematical function could be obtained between the variability and the interstation distance. Nevertheless limiting the analysis to pairing of the same hillside, the authors found a correlation between variability and elevation difference between pairs of stations. To quantify the influence of temporal scale on the spatial variability, the authors have analyzed different integration periods from daily to 10-min values. The study of shortest temporal scales reveals that the short-term variability introduced by cloudy conditions markedly influences the spatial variability. The results of this study are relevant for those interested in the accuracy of satellite-estimated irradiances and for those interested in interpolating measured irradiances from existing networks or establishing an irradiance measurement network in highly heterogeneous areas.