Densification of Seasonal Snow Cover

The theory of densification of snow, which is based on an empirical relation between the compactive viscosity factor and the density, has been applied to the numerical computations of depthdensity profiles of snow cover under various conditions of mass accumulation of snow. This paper is concerned with the theoretical computations of time variation of density profiles of snow and the depth of seasonal snow cover under varying accumulation rates, where Sorge's law does not hold. The computed results are found to be in good agreement with the data observed in Sapporo and Moshiri, Hokkaido. Densification of slightly wet snow is found to occur at nearly the same rate as that for dry snow of O°C, while very wet snow with a water content of more than 10% is very rapidly compacted until it changes to granular snow of large grains and its viscosity reaches a considerably high value. The compactive viscosity of wind-packed snow with very fine grains is much smaller than that for ordinary compact snow of the same density, particularly in the early stage of densification. The influence of formation of depth-hoar crystals in snow upon the densification behavior is also reported. To examine the validity of the linear relation between the strain rate and the load, a field experiment was made by strain rate measurements of some selected snow layers subtracting or adding the snow load artificially. The results for some layers show linear relations between them within the error of measurements, while the linear relation could not be obtained for the layers very close to the surface of snow cover.