Journal of the Japanese Society of Snow and Ice

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The aim of this research is to investigate the advantages of rice husk as an insulation material for long-term snow storage. This paper describes the heat balance model of the rice husk surface and the heat conduction analysis of the rice husk layer based on the open-air snow pile storage experiment and measurements of the properties in the first report (Kamimura et al., 2007). Measurement of the net radiation shows the following results : approximately 25% of the maximum solar radiation of 800 Wm -2 on a sunny day is reflected directly from the surface into the air, and the same amount of energy is emitted as long-wave radiation into the air. The average surface albedo of rice husk is 0.75 and increases with time, ranging from 0.65 to 0.85 . The energy of of the net radiation is absorbed at the surface, released into the air by sensible and/or latent heat transfer, and the remaining 8-10% flows into the snow pile through the rice husk layer. The temperature profile of the rice husk layer was simulated by using one-dimensional, non-steady heat conduction analysis, and it was found to agree well with the temperature profile observed outside the experiment. Since the surface temperature estimated by the calculation of heat conduction is 15℃ below that recorded by a radiation meter, it is considered that another heat transfer phenomenon, which cannot account for the heat conduction model, occurs at the neighboring surface layer. Long-term simulations of the decrease in the height of the snow pile agree well with the observation results. Further, it is shown that the heat transferred by rain may not contribute toward the deformation of the snow pile but toward the creation of holes.

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We collected rime samples on Mt. Zao (near the summit of Mt. Jizo) in two winter seasons (2002-2003 and 2003-2004) and major ionic components and sulfur isotope ratio of sulfate were measured. As a result, almost all the rime samples were obtained under the strong winter climate conditions associated with the flow of the northwestern monsoon from the Asian continent to Mt. Zao. The ∂34S values of non-sea salt sulfate in the rime samples ranged from 4 to 8 ‰ , and almost all the sulfur that originated naturally were transported from the sea. It appears that the formation of sulfur in rime is a result of the mixing of two components (sea water and anthropogenic sulfur). The results obtained indicate the strong possibility of long-range transport from the Asian continent to Mt. Zao through the lower troposphere.

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