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Volume 66 (2004)
- Issue 6 Pages 623-
- Issue 5 Pages 541-
- Issue 4 Pages 463-
- Issue 3 Pages 341-
- Issue 2 Pages 149-
- Issue 1 Pages 3-
Volume 66, Issue 6
Displaying 1-6 of 6 articles from this issue
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Kunio RIKIISHI, Yasuto TAKAMORI, Shingo MIYAHATA, Yumi HANDA2004 Volume 66 Issue 6 Pages 623-636
Published: November 15, 2004
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSA comparative study is made of the characteristics of snowfalls in Hokkaido and Honshu by using climatological data of meteorological observations, daily snowfall observations by acoustic snow-depth meter, and objectively analyzed upper air observations by the National Meteorological Center, USA. It is shown that relatively light snowfalls are frequently observed in Hokkaido while relatively heavy snowfalls are occasionally observed in Honshu, especially in the Hokuriku Region. Snowfalls in Hokkaido generally show poor correlation with those in Honshu, and areas of high correlation are limited within the neighborhood of reference stations. On the other hand, snowfalls at a reference station in Honshu show high correlations even with those at distant stations. In this case, however, the area of high correlation is observed along coastal plains or along inland plains, depending on the location of the reference station. Finally it is shown that snowfalls in Honshu show significant negative correlations with the sea level pressure and 500 hPa geopotential height fields, whereas snowfalls in Hokaido do not show any correlations with the above fields.
These remarkable differences in the characteristics of snowfalls in Hokkaido and Honshu may partly be ascribed to the fact that snowfall in Honshu is generally caused by an extensive southeastward extension of the cold air flow (winter monsoon) while snowfall in Hokkaido is strongly influenced by moving synoptic lows whose intensities and traveling routes toward the Bering Sea considerably vary from one case to another.View full abstractDownload PDF (12758K) -
Part 1 A measurement method of diameter and fall speed by image processingToru SHIINA, Masaaki ISHIZAKA, Ken-ichiro MURAMOTO, Sento NAKAI, Atsus ...2004 Volume 66 Issue 6 Pages 637-646
Published: November 15, 2004
Released on J-STAGE: August 07, 2009
JOURNAL FREE ACCESSThis proposed technique is not only useful to observe snowfall quantitatively, but also to measure the kind and quality of solid precipitation. This study focuses on measurement of the diameter and terminal velocity of falling snow particles. The CCD camera has a high shutter speed (1/4000s) so that the shape of each particle can be obtained. Since it is not possible to measure fall velocity using the afterimage of a particle, a new image analysis technique is required. This paper proposes a new image technique to measure fall velocity of snow particles.The results of measurements using these techniques are compared.View full abstractDownload PDF (8599K) -
Part 2 Verification of the method applied to a variety of solid precipitations observed at NagaokaMasaaki ISHIZAKA, Toru SHIINA, Sento NAKAI, Atsushi SATO, Katsushi IWA ...2004 Volume 66 Issue 6 Pages 647-659
Published: November 15, 2004
Released on J-STAGE: August 07, 2009
JOURNAL FREE ACCESSFor continuous observation of snow particle types an automated falling snow acquisition system was constructed. In the system, images of solid precipitations, which fell into a space enclosed by fences for protection against the wind, were taken by a CCD video camera with high shutter speed (1/4000 sec) and were input into an image processor in the computer continuously. After image processing, numerical data of each particle were recorded, i.e. locations, both horizontal and vertical dimensions and contour data of cross section of the particles on the image etc. An algorithm for computing the fall speed of each particle from the images was also developed. Operating this system in the winters of 2002 and 2004, we simultaneously carried out detailed observations of snow particles with a microscope and observed various types of snow, i.e. various kinds of aggregates with different riming stages and different types of graupels. Comparing the detaied manned observations and numerical data obtained by the system, it is found that we can clarify the types of falling snow particles from the relationships between dimension and fall speed of snow particles reduced from numerical data. In this article we show how the types of particles can be detected by the system using many microscopic photographs of solid precipitation.View full abstractDownload PDF (16395K) -
Tsutomu KOKAWA2004 Volume 66 Issue 6 Pages 661-668
Published: November 15, 2004
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSThis paper describes a numerical investigation of structural safety when the ice dome is subjected to a concentrated load such as a human live load on the apex. Regarding the problem as a short-term loading and the elastic behavior of ice, the elastic solution is based on the theory of a spherical shallow shell under a uniformly small circular load. Both the cases of single load and twin loads on a dome are investigated, assuming that the ice dome will break when the tensile stress reaches a certain maximum value. Estimating that the weight of a human is 100 kg and the allowable stress of the ice is 3kg/cm2, where the bending strength is 10kg/cm2, it is concluded that the minimum thickness of the ice becomes 6 cm under a 15 m span, and 7cm over a 15 m to 30 m span, even though the distance is 1m in case of twin loads.View full abstractDownload PDF (903K) -
Katsumi YAMANOI, Yukari TAKEUCHI, Shigeki MURAKAMI2004 Volume 66 Issue 6 Pages 669-676
Published: November 15, 2004
Released on J-STAGE: August 07, 2009
JOURNAL FREE ACCESSIt is necessary to obtain the shear strength of the snow pack promptly, in detail and conveniently in an avalanche disaster investigation. A method of determining shear strength from hardness measured with a handy-type digital load-gauge (push-gauge) is developed. The shear strength, which does not depend on snow type, is proportional to the 1.18 power of the hardness. Shear strength and stability index were calculated using this equation on several investigated avalanches. A weak layer of stability index 1.5 or less agreed with the bed surface of an avalanche. Therefore this technique is effective in avalanche investigation.View full abstractDownload PDF (8053K) -
Heat balance model and heat load diagramSeiji KAMIMURA, Shingo HOSHINO2004 Volume 66 Issue 6 Pages 677-692
Published: November 15, 2004
Released on J-STAGE: February 05, 2010
JOURNAL FREE ACCESSThe design heat load of snow-melting facilities is considered in this paper.
First, a heat balance model of a pavement surface is constructed. It uses only easily obtainable meteorological data. The model is applied to hourly simulation. Spatial and temporal nonuniformity of snow condition on the surface are simplified to the two extreme situations of “exposed” and “covered with snow” on the surface.
Second, frequency distributions of heat load during January and February of 11 winters are calculated at 6 representative points: Sapporo, Aomori, Akita, Niigata, Nagaoka and Toyama. At Sapporo, Aomori and Akita are relatively cold areas in Japan, the heat load on an exposed surface is greater than on a surface covered with snow, conversely heat load on a snow covered surface is greater at Niigata, Nagaoka and Toyama. It is also shown that unrealistic heat load could be needed to keep the road surface snowfree 100 % of the time.
Finally, two parameters, the snow-free hour ratio .φ and the design snowfall time δ, are introduced to represent the service level of pavement. A diagram to determine the design heat load having φ and δ axis, named the“φ-δ diagram”, is proposed. Calculation of heat load under the standard condition(δ, φ)=(3h, 80%), shows that it is less than a practical value of heat load. It is concluded that the standard condition should be modified to (3h, 90%) or (1h, 80%) for a normal service area and (3h, 95%) or (1h, 90%) for important area, respectively.View full abstractDownload PDF (5523K)
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