Journal of the Japanese Society of Snow and Ice

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The paper presents a snow depth simulation model on a snow melting surface of a far-infrared snow melting system installed on a snowfall prevention fence at the entrance of Shibahara Tunnel on Route 17, and examines its optimum operating conditions. The model is based on the Degree-day method and uses only hourly temperature, precipitation, and natural snow depth data. The optimum operating conditions were estimated by inputting weather data from winter 2012 into this model. The results reveal that the snow melting capacity of 100Wm−2 and the snow depth binary control (drive at 250 cm, stop at 200cm) were optimal. In addition, a model considering an avalanche was built (when an avalanche judgment occurs, the snow depth in front of the fence increases by 14.7 cm). Even in the year with two avalanche predictions in one winter, the snow depth can be maintained below the allowable snow depth of 300cm by melting snow under the optimum operating conditions. Furthermore, the cost of the snow melting system for 10 years was calculated. The electricity price is expected to be reduced by about 568 thousand yen in 10 years by using the snow depth binary control and by changing the electricity price contract to a plan with a low basic fee. Even considering the initial investment and maintenance costs, the cost of the far-infrared snow melting system is estimated to be about 7900 thousand yen cheaper than the cost of manual snow removal.

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A thermal ice ridge is a height upheaval of ice, like a dragonʼs dorsal fin, along cracks in a frozen lake (Figure 1). Omiwatari (or Godʼs Crossing), or thermal ice ridges, were considered to result from an increase in ice temperature leading to thermal expansion of the ice plates. However, Hamaguchi (2009) recently collected data on Lake Suwa (36° 03'N, 138° 05'E) from the perspective of volcano physics and seismology and proposed a new theory (based on a volume increase at the phase change from water to ice) stating that the ridges form when the air temperature drops, thus reversing the traditional theory. In this study, we use quantitative observation and thermal ice ridge outbreak pictures captured by a video camera with a crack width of the thermal ice ridge of Lake Kussharo (43° 37'N, 144° 20'E) and inspection through more recent observations at the actual site. Our results reveal that new ice was generated on an open surface of water due to shrinkage of the ice plate cooled at night, and a thermal ice ridge occurred from expansion of the ice plate when the ice temperature rose during the daytime. In addition, although the conventional study focused only on generation of thermal ice ridges, this report aims to acquire an observational record of later development of thermal ice ridges after generation, successfully clarifying a basic process of such development of thermal ice ridges.

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