Journal of the Japanese Society of Snow and Ice

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Secular changes of some parameters affecting the properties of snow sliding on steel roof sheets, such as static and dynamic friction coefficients, microstructures, the surface roughness and the degree of luster, have been studied for six kinds of steel roof sheets which are usually used in a heavy snow-fall district. Using these data, we have tried to predict secular changes of properties of snow sliding for those roof sheets. Comparisons were made between the prediction and the results of outdoor experiments. The results obtained are summarized as follows. (1) Secular changes of static and dynamic friction coefficients, changes in surface roughness, and changes in the degree of luster are closely related to secular changes of microstructures of roof surfaces. (2) The frictional properties of steel roof sheets for hard snow resemble closely those for ice. (3) The rate of secular change of the static friction coefficient for each roof sheet is in proportion to that of the dynamic friction coefficient. (4) The validity of the prediction, that secularly changed steel roof sheets having lower values of friction coefficient would show better properties of snow sliding, was confirmed by the results of outdoor experiments over three winter seasons.

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Snow albedo was parameterized with the surface snow density in the top 5 cm of snow cover. In the model the effects of impurities and liquid water content in the snow cover is considered. Good agreement was found between the calculated albedo and the observed one within ±0.05. Combining this model with a snow density model (Kondo and Numata, 1988) the snow albedo can be expressed as functions of the number of days and the mean air temperature after the last snowfall.

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