Implications of spatial distributions of snow mass and melt rate for snow-cover depletion: theoretical considerations

Abstract

AbstractSnow becomes patchy while melting, giving a heterogeneous surface with large contrasts in characteristics such as albedo. It is therefore necessary for surface schemes used in atmospheric and hydrological models to represent the influence of heterogeneities in snow cover on scales smaller than the model grid; this is typically done by introducing a snow-cover depletion (SCD) curve relating fractional snow cover to average depth. Here, ad hoc functional forms which have been used for this relationship are first compared with forms obtained for an assumed initial snow distribution undergoing homogeneous melt. The energy available for melt may be heterogeneous, however, and can be influenced by factors that also influence snow distribution, such as slope, aspect and vegetation cover. The modification of SCD curves by spatial variations in melt energy is investigated, and resulting curves are found to be similar to those which would be given by homogeneous melting of a snow cover with greater initial variance. This influence is increased by any negative correlation between snow depth and melt rate.