Decoupling the effects of clouds and clear atmosphere to compute the solar irradiance at surface

摘要: This work contributes to the research of fast calculations surface solar irradiance (SSI) I and proposes a general equation that decouples effects clear atmosphere on its direct (B) diffuse (D) components from those due clouds. These are studied numerically in case infinite plane-parallel single-layered cloud. The dependency ratios / Ic B Bc is as function clear-sky parameters, where global SSI under clear-sky. To extent, large set atmosphere, clouds properties has been created, which statistically represent conditions encountered worldwide with their respective probabilities. Many possible combinations randomly extracted input radiative transfer model libRadtran, yielding corresponding series I, B, D, Bc. influence clear-atmosphere cloudy quantify how small this compared It found can be approximated by product for null ground albedo modification factor cloud only no properties. errors made mapped against albedo, optical depth zenith angle, latter most prominent variable. maximum error (percentile 95%) less than 5% angles 70° all cases 15 W/m2 albedos 0.7. practical approximation convenient developing any computational chain since whole processing separated two independent models whose inputs different.