Macro-scale Modelling of Shortwave Radiative Flux over Land Surface with Undulation

Abstract

To incorporate land surface schemes into climate models adequately, a method for aggregation of hydrological processes on large area with heterogeneity, a macro-scale hydrological model, has to be developed. Shortwave radiation is one of the most important factor for land surface hydrological processes. Because of topographic variability on land surface, however, it is difficult to evaluate the incident solar radiation flux over land surface with undulation. This study present a method to calculate spatially averaged shortwave radiation flux on land surface with undulation. We use an “Insolation Receiving Rate (IRR)” at each slope for estimation of the effect of slope inclination and aspect, and propose a macro-scale IRR which expresses the variance of IRR in a large area in addition to the average value. Finally, we evaluate the effect of spatial variability of IRR on evaporation and snowmelt.