Small-scale variabilities of solar irradiance are important for many applications. Downscaling approaches need to be developed where only the averaged state of solar irradiance is known. In this study, we investigate the use of copula for temporally downscaling GHI clear-sky indices. With the correlation structure and distribution information derived from measurements at 10 stations across the United States, the copula approach is capable of downscaling clear-sky indices from hourly averages to any arbitrary fine scale whilst preserving its original power spectra.

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