Measurement of snow-hardness distribution

Abstract

Disitributions of snow hardness minutely measured with a bandy-type digital load-gauge (push–pull gauge) are demonstrated. This push-pull gauge is of compact design and is useful for precise measurement of tension and compression loads. It can measure the maximum strength of a snowpack when it is destroyed by the attachment pushed horizontally into the side of the pit. Because it takes only a few seconds for one measurement, snow-hardness distribution can be measured at very small space intervals more quickly and with less effort than by using any previous hardness meter, such as a rammsonde, Canadian gauge, Kinosita-type hardness meter, and so on.Snow-pit observations were made at Saiho, Sapporo and Minakami, Japan, in the winter seasons of 1996 and 1997. The snow hardness was measured with the push-pull gauge at regular intervals of 5 cm vertically and 10 cm horizontally. Some weak layers between harder layers could be detected with the push-pull gauge whereas they could not be using the rammsonde. The hardness of snow was observed to be almost uniform horizontally before snowmelt. Once meltwater infiltrated into the snowpack, its distribution became heterogeneous. It was revealed that the hardness of the fine-grained compacted snow layer with grain-sizes less than 0.5 mm showed a high correlation with the fourth power of the snow density.