Effects of temperature and grain type on time variation of snow specific surface area

The specific surface area (SSA) of snow is of particular interest to researchers because SSA is strongly related to snow albedo and is a comparatively better indicator of snow's complexity than grain size. The time variation of SSA for fresh snow samples was observed in the laboratory under isothermal conditions at 226 K and 254 K using the gas adsorption method and Brunauer-Emmett-Teller theory. The SSA of the snow samples decreased with time under isothermal metamorphism. The decrease in SSA was fitted with the logarithmic equation proposed by Legagneux et al. (2003), and adjustable parameters were obtained. The rate of decrease in SSA depended on the shape of the initial snow type and temperature. Dendritic snow samples exhibited large initial SSAs, and their SSAs decreased faster compared with those of fragmented (collected from drifting snow) and plate-like precipitation particles with relatively small initial SSAs. The rate of decrease in SSA was lower at 226 K than that at 254 K.