Multiscale modeling of heat and mass transfer in dry snow: influence of the condensation coefficient and comparison with experiments

Temperature gradient metamorphism in dry snow is driven by heat and water vapor transfer through snow, which includes conduction/diffusion processes in both air and ice phases, as well as sublimation and deposition at the ice-air interface. The latter processes are driven by the condensation coefficient alpha, a poorly constrained parameter in the literature. In the present paper, we use an upscaling method to derive heat and mass transfer models at the snow layer scale for values of alpha in the range 10-10 to 1. A transition alpha value arises, of the order of 10-4, for typical snow microstructures (characteristic length similar to 0.5 mm), such that the vapor transport is limited by sublimation-deposition below that value and by diffusion above it. Accordingly, different macroscopic models with specific domains of validity with respect to alpha values are derived. A comprehensive evaluation of the models is presented by comparison with three experimental datasets, as well as with pore-scale simulations using a simplified microstructure. The models reproduce the two main features of the experiments: the non-linear temperature profiles, with enhanced values in the center of the snow layer, and the mass transfer, with an abrupt basal mass loss. However, both features are underestimated overall by the models when compared to the experimental data. We investigate possible causes of these discrepancies and suggest potential improvements for the modeling of heat and mass transport in dry snow.