Air Permeability as a Textural Indicator of Snow

Two air-permeability devices were developed and mea­ surements were made to study the relationship between air permeability and structure of different snow lypes. Permeabilities varied both with position and direction in the snow-pack, and changed with time as meta­ morphic changes occurred. A marked increase of air permeability was noted as faceted crystals grew due to radiation recrystallizatio n. In other obser­ vations, as a snow-pack densified and crystals became more rounded (des­ tructive metamorphism) the air permeability decrea:sed. Measurements were made of air permeability of snows that had been subjected to a creeping tensile strain, and initial tests indicated that the changes in air permeability due to strain, even to rupture, were significant, but small compared with the intrinsic variability of snow.