Study on quantitative classification of seasonal snow using specific surface area and intrinsic permeability

The release mechanism of snow avalanches depends on the mechanical properties of snow, which are closely related to snow microstructure. Previous observations show that snow microstructure can be described qualitatively on the basis of snow types. However, the qualitative determination of snow types may become subjective. Therefore, it is essential to quantitatively classify snow. The specific surface area (SSA) and intrinsic permeability (k0) are closely related to the snow microstructure. In particular, we believe that the former parameter reflects the features of the grains, and the latter parameter indicates the characteristics of the pores. Measurements of the specific surface area per unit snow volume (SSAV) and the intrinsic permeability were performed on the naturally deposited dry snow in Hokkaido prefecture, Japan, during the winter of 2007–2008. SSAV was measured using a stereological method, where the section planes of snow samples were prepared, imaged, and analyzed, and the SSA per unit mass (SSAM) was obtained by dividing SSAV by the snow density. The value of SSAV indicates only the area size, while the value of SSAM indicates the snow microstructure. k0 was measured in situ using an air permeameter with a double cylinder, and it was calculated assuming a laminar flow in order to satisfy Darcyʹs law. The results showed that the correlation between SSAM and k0 could be used to clearly distinguish the snow types. In addition, we could confirm certain changes in SSAM and k0 accompanied by the occurrence of the two processes of temperature gradient and melt-freezing metamorphism, which occur in the snow cover.