Shunsuke SAITOH
A study on the terrain effects by winter monsoon in Hokuriku, JAPAN for estimating snow depth
Toshiro KUMAKURA
Large amount of snow in snowy mountains is naturally stored by snowfall and become the resources of fresh water. In practice, it is very difficult to observe the snow depth on the steep slope and the high altitude mountain regions, though understanding its dynamical behaviors and its distribution is important. According to the previous studies, it is suggested that ADSD (Altitude Dependence of Snow Depth) is different between the windward and leeward regions which are difficult to delineate each other. Then, we clarify the delineating method using the inner product between the diagnostic wind vector from numerical weather model and ridge-ward vector from elevation data and define two regions: Region A which has the large relief of the mountains and Region B which has the small relief. We find that the Region A has the large difference of the ADSD between the windward and leeward in the Region A, on the other hand, Reagion B has small difference. It is suggested that the snow depth on the leeward slopes is affected by amount of remaining moisture which do not fall on the windward slopes as the snowfall. Finally we attempt to use multiple regression analysis with the functions of the altitude, distance from observation point to the coastline, the sum of the upward angles of the slopes on windward along the path from the coastline, and the local relief amount. We obtain good results at the windward region in the Region A which has the determination coefficient 0.97 and root mean square error 22.7 cm and also find the improvements at the windward and leeward regions in the Region B. It is suggested that the separation of the windward and leeward regions of the wind is very important to estimate the snow depth, and especially in the Region A the snow depth can describe with only the factors due to the reliefs of the mountains.
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