Journal of the Japanese Society of Snow and Ice

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　Based on 15 years of snow pit observation data in Sugadaira Highland, the year-to-year variations of weather patterns influencing the snowpack properties were examined. A significant relation between the snow depth in mid-February and the total precipitation after persistent snow cover was found. The ratio of the total thickness of melt forms in the snow cover depth and the tendency of ice layer formation showed large year-to-year variations with significant correlations with the mean surface air temperature and frequency of rain on snow (ROS). The dating of the major layer’s formations, estimated by AMeDAS data, was mostly associated with ROS events from extratropical cyclones. Five patterns representing the intraseasonal variation of weather and snow cover conditions were statistically identified by factor analysis using the monthly base temperature, precipitation, maximum snow depth, and starting (ending) snow cover periods from December to March for 31 winters since 1991-92. The pattern indicating air temperature variabilities with ending date of the snow cover period showed a warmer/earlier tendency, and the pattern indicating a warmer January with frequent ROS events showed decadal scale periodicity. Snow cover profiles for 15 winters were simulated using the physical SNOWPACK model. In the model, ROS event days initiated the melt form layers, and the year-to-year variation of melt forms thickness ratio by the full snow-pit observations was almost reproduced.

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