Shortwave radiative transfer modeling at large scale for partial cloudy conditions

Clouds are the strongest modulator of the solar radiation absorbed by the earth-atmosphere system. In this study, a regional cloud fraction (RCF) is involved to modify the classic one-dimensional radiative transfer model, in order to study the effect of inner-pixel broken clouds on the radiation field at large scale. A global sensitivity analysis (GSA) is performed to quantitatively understand the effect of 11 parameters on each surface shortwave radiation component. The GSA results show that three most influential parameters for the modified model are RCF, land surface albedo and solar zenith angle. Three less important parameters are ground altitude, visibility and cloud extinction coefficient which is the case only for the situation of optically thin clouds. The other five factors can be considered as not important. These findings will enhance our knowledge on how to accurately model the surface shortwave radiation fluxes at large scale for partial cloudy conditions.