Stratigraphy and changes in hardness of snow measured by hand, ramsonde and snow micro penetrometer: a comparison with planar sections

Abstract

Snow stratigraphy and changes in snow hardness are amongst the most important parameters in the study of snow. In seven snow pits, three types of hardness tests were performed: these were hand, ram and micro penetrometer tests. The stratigraphy, in terms of layers and layer boundaries, was established from planar sections at a high spatial resolution, providing an objective reference for comparison with the analysed profiles. The snow layers and layer boundaries from the hardness profiles were compared with planar section stratigraphy. The hand test captured 80% of all layers and layer boundaries and the ram test 60%, and the micro penetrometer captured all the identified layers. Hand and ram profiles can only be used to determine an average hardness and stratigraphy. Important details are missed such as soft and thin hard layers, which are particularly significant for avalanche formation. Quantitative evaluation of mechanical and textural snowpack properties requires objective measurements with a spatial resolution of at least 1 mm. Since the predominant heat and mass fluxes are perpendicular to the snow surface, the more detailed stratification shown with the micro penetrometer has significant implications for mass and heat transfer within the snowpack. Numerical models not representing this small-scale layering will be misleading. Avalanche formation, snow hydrology and electromagnetic modelling (microwave emission and radar) are other examples of areas where a good resolution of the snowpack stratigraphy is important.