Modeling topographic effects on snowmelt with adapted degree-day model applying MODIS data

The temperature-index method is a very popular concept for modeling snowmelt, by which temperature is used as surrogate of the energy input for snowmelt. Although the method performs reasonably well in some cases, it is not able to account for the spatial variability of the energy input modulated by topography, except for the elevation through the lapse rate in a distributed model structure. This work attempts to incorporate the spatial radiation variability caused by topographic effects into the distributed degree-day model, in both additive and multiplicative formulations. Different radiation components are investigated, from potential solar radiation to actual solar radiation and from shortwave radiation to all-wave radiation. The implemented degree-day models are calibrated at the stations with the binary MODIS snow cover data, observed temperature and precipitation data, and validated with spatially interpolated temperature and precipitation data, as well as MODIS data. Comparison of the results of the adapted models with the standard degree-day model shows an improvement of the model performance.