LOCAL-SCALE VARIABILITY OF SOLAR-RADIATION IN A MOUNTAINOUS REGION

Simultaneous measurements of horizontal global solar irradiance and ot her meteorological parameters have been taken over three years at a de nse radiometric network. The network is located on a mountainous regio n in southeastern Spain (37 degrees N, 3 degrees W) covering elevation s 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 heterogen eity of the area is reflected in the great spatial variability encount ered. The purpose of the study is to obtain an estimate of the small-s cale variability of the daily, hourly, and shorter-settle solar irradi ance values. Following previous results at a similar spatial scale, no mathematical function could be obtained between the variability and t he interstation distance. Nevertheless, limiting the analysis to pairi ngs of the same hillside, the authors found a correlation between vari ability and elevation difference between pairs of stations. To quantif y the influence of temporal scale on the spatial variability, the auth ors have analyzed different integration periods from daily to 10-min v alues. The study of shortest temporal scales reveals that the short-te rm 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 h eterogeneous areas.