Journal of the Japanese Society of Snow and Ice
Online ISSN : 1883-6267
Print ISSN : 0373-1006
Volume 48, Issue 4
Displaying 1-4 of 4 articles from this issue
  • Yusuke FUKUSHIMA
    1986 Volume 48 Issue 4 Pages 189-197
    Published: December 30, 1986
    Released on J-STAGE: February 05, 2010
    JOURNAL FREE ACCESS
    Appropriate expressions describing the motion of powder snow avalanches are derived. The model consists of four equations, i.e. the conservation equations of air, snow particles, momentum of avalanches, and kinetic energy of turbulence. The total buoyancy of powder snow avalanches changes freely via erosion and deposition of bed material. In the model presented, the snow entrainment rate from bed is directly linked to the level of tubulence.
    The rate of development of strongly accelerated avalanches is obtained with the aid of numerical integration. The model gives a good explanation of the characteristics of the powder snow avalanche, i.e. the quick formation of thick clouds and the very fast speed of the front. To the extent that observations exist, the prediction of powder snow avalanches obtained herein is in general agreement with those observations.
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  • Kaoru IZUMI, Eizi AKITAYA
    1986 Volume 48 Issue 4 Pages 199-206
    Published: December 30, 1986
    Released on J-STAGE: August 07, 2009
    JOURNAL FREE ACCESS
    Akitaya and Endo (1980, 1982) developed a calculating expression for deciding whether depth hoar grew in the snow cover in Hokkaido, using averages of snow depth and air temperature during January and February in individual districts. As for Honshu, Japan's largest island, to the south of Hokkaido, almost no record of depth hoar in the snow cover is available. Thus, we applied this expression there, using meteorological data, from which it followed that depth hoar was likely to develop in the snow cover in several districts of Honshu. By actually surveying the snow cover in eight of these districts, we confirmed the development of fragile depth hoar in the lower part of the snow cover. As a result, this expression proved to be applicable in Honshu, as well.
    Then, we examined the meteorological data of all Japan except Hokkaido, with a finding of more than 40 districts where depth hoar developed in the snow cover in more than two of the recent ten winters, almost all of them being in Honshu, not other islands. They are on the Pacific Ocean side of the backbone ranges of Honshu, having a little snow and low temperature in winter. They distribute in the southeastern part of Aomori Prefecture and almost all parts of Iwate Prefecture, both of northern Honshu, as well as, in central Honshu in such districts as highlands and the eastern side of mountain ranges or high mountains forming terrain obstacle to the northwesterly monsoon.
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  • VIII. Blocking of snow/water mixture flow and criterion of stagnation of snow at pipe orifice
    Teruyoshi UMEMURA, Mikio NAKAYAMA, Akira UCHIYAMA, Yasushi TOKUNAGA, M ...
    1986 Volume 48 Issue 4 Pages 207-214
    Published: December 30, 1986
    Released on J-STAGE: February 05, 2010
    JOURNAL FREE ACCESS
    Based on observations of flows, an outline of the blocking phenomenon of snow/water mixture flow in closed channels was given. It was confirmed that a characteristic blocking occurred due to the property of snow in the mixture flow, i.e. a tendency of snow blocks to adhere to each other and to form a densified plug in the channel compressed by the water pressure. Since the blocking was revealed to originate from the stagnation of the snow cluster, the criterion at on orifice in a horizontal pipe was investigated experimentally. With pipe diameter D=47∼90 mm and the areal contraction ratio K=0.068∼0.27, the dependence of the critical flow velocity Vst (below which snow clusters were arrested at the orifice) on D, on K, on snow volume fraction C in discharge, and on the property of snow was made clear as follows.
    (1) When C<C*, where C* is 0.15 and 0.12 for granulated snow and fresh snow respectively, Vst is inversely proportional to D and independent of C. When C>C*, snow clusters almost fill the pipe and Vst is inversely proportional to D and proportional to C. While, the influence of K on Vst is not significant over the whole experimental range of C.
    (2) Fresn snow is apt to stagnate, and the critical values of DVst with C<C* and DVst/C with C>C* for fresh snow are 1.4 and 2 times the corresponding ones for granulated snow.
    (3) Blocking is avoidable by applying the critical values of DVst or DVst/C obtained in this work as the criterion of stagnation.
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  • Tatsumi SASAKI
    1986 Volume 48 Issue 4 Pages 215-221
    Published: December 30, 1986
    Released on J-STAGE: February 05, 2010
    JOURNAL FREE ACCESS
    Ice ramparts develop mainly on the shores of inland lakes which are frozen over in winter. In this paper, an explanation is made of these micro-relief features. Shapes, sizes and internal structures of these features are described and the mechanism of their formation is also discussed.
    Many synonyms for“ice rampart”are found in previous papers.It is, therefore, apprehended that a multiplicity of terms may cause much confusion in studies on ice ramparts. The author proposes his personal view on the usage of technical terms which are concerned with these features.
    Since the early 1820's numerous studies on ice ramparts have been done. The history of these studies can be divided into three periods:“early studies”, “studies after Gilbert”and“recent studies”. An outline of each period is given, and lastly trends in recent studies on ice ramparts are briefly summarized.
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