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Volume 77, Issue 1
Displaying 1-7 of 7 articles from this issue
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Hiroyuki HIRASHIMA, Satoru YAMAGUCHI, Kenji KOSUGI, Masaki NEMOTO, Ter ...2015 Volume 77 Issue 1 Pages 5-16
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSSnow profiles simulated by the numerical model SNOWPACK were compared with the results of snow pit observations. Comparisons were performed for three regions：(1) Nagaoka, a warm and wet snow region, (2) Shinjo, a dry snow region, and (3) Sapporo, a cold snow region. The purpose of this study was to determine the discrepancy between the simulated and observed results and to discuss methods to effectively improve the accuracy. Average values, standard deviations, and weighted centers of snow temperatures, snow densities, grain sizes, and water contents were calculated for observed and simulated snow profiles to perform quantitative comparisons. Furthermore, adjustment of parameterization for albedo was performed using observed data to minimize the discrepancy caused by the albedo in the snow profile. Adjustment of parameterization showed that the albedo should be parameterized to be lower in wet snow regions than in dry snow regions. Simulated snow profiles agreed well with the observed snow profiles. In the analysis of determining the discrepancies, underestimation of heat conduction, densities, and grain size for fresh snow were found. Heterogeneity of water content was also underestimated. Our results indicate that improvement of thermal conductivity and viscosity coefficient for fresh snow and incorporation of the influence of preferential flow are necessary to effectively enhance the accuracy of SNOWPACK.View full abstractDownload PDF (1375K) -
Shinji IKEDA2015 Volume 77 Issue 1 Pages 17-35
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSOn January 25, 2009, a snowboarder was caught and injured seriously by an avalanche that occurred at Mumeizawa, Japan. The formation process and spatial distribution of the snow instability that caused this avalanche were examined based on the avalanche fracture line profile, snow and avalanche condition records from around the accident site, and snow profile data collected over a wide area. The instability was caused by the snowpack structure, which included a 40-cm-thick slab consisting of new snow and rounded grains, and a 2-cm-thick weak layer consisting of large rime-less plate-like new snow crystals. The weak layer was, formed over a large area in association with the passing of low pressure during January 22-23；however, this weak layer was stabilized immediately by solar radiation at the sunny side slopes. Conversely, the slab was formed within a limited area of the Japan Sea side mountain range in association with the Japan Sea effects snowfall. Therefore, it is presumed that the snow instability that caused the accident existed only over a limited high-elevation area in the shady side slopes. Furthermore, based on the analysis of observations along the Mumeizawa avalanche fracture line profile combined with extra observations and observations which collected from previous researches, it is suggested that weak layers composed of large rime-less plate-like crystals persisted longer than the layers composed of other precipitation particles.View full abstractDownload PDF (5488K) -
Osamu ABE, Hiroyuki HIRASHIMA2015 Volume 77 Issue 1 Pages 37-45
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSThe National Research Institute for Earth Science and Disaster Prevention is improving an avalanche forecasting system based on the SNOWPACK model, which was developed by the Swiss Federal Institute for Forest, Snow and Landscape. It has been difficult to forecast avalanches caused by depth hoar (including faceted crystals) with high accuracy while using this system due to the wide range of shear strength. We previously proposed a model to estimate the shear strength during each stage of development for faceted crystals. In the present study, the avalanche forecasting system and the previously proposed model were used to calculate the stability index (SI) at the release zones of five avalanches that were observed in mountainous areas. Meteorological data from the station closest to each release zone were used as the input data of the system. In four of the five cases, a weak layer consisting of faceted crystals was reproduced for each release zone, and the calculated SI ranged from 1.1 to 2.7, which are values that indicate the occurrence of slab avalanches. This system was confirmed to be applicable to the forecasting of avalanches in mountainous areas, but only if a weather station is located near the avalanche release zone.View full abstractDownload PDF (2826K) -
Kazuya AKIYAMA, Tatsuo SEKIGUCHI, Shinji IKEDA2015 Volume 77 Issue 1 Pages 47-57
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSHeavy snowfall was recorded in the Kanto-Koshin region, Japan, from 14 to 15 February 2014. It snowed heavily throughout Yamanashi Prefecture, and many avalanches occurred in various places. Surveys performed along the Hayakawa River across Hayakawa Town from a helicopter on 22 February and from the ground on 19March indicated that avalanches, including unclear avalanche release areas, had occurred at 80 locations and 23 surface-layer and 57 full-depth avalanches were identified. These avalanches were released from collapsed sites or deciduous forest and ran out along streams or concave slopes. Based on 60 avalanches tracked with traces from the release zone to deposit zone, the horizontal run-out distance was up to 500m for surface-layer avalanches and up to 700m for full-depth avalanches. The inclination of the release zone of the avalanches ranged mostly from 35-50° and the direct angle of elevation from the outer end of the deposit zone to the highest point of the release zone of the avalanches (α angle) ranged upward from 34°.View full abstractDownload PDF (6172K) -
Masashi KAWABATA, Toshihiro OZEKI, Kenji KOSUGI, Atsushi SAKUMA, Shige ...2015 Volume 77 Issue 1 Pages 59-66
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSIn this study, we researched the skier's zone of influence in the new snow cover of low-density. After we fixed a pressure sensor to the snowfall table on flat ground, we simulated snowfall and prepared the snow cover. We measured the increase in pressure on the snow cover by the skier's crushing load. The purpose of this study is to compare the layering of the snow cover: low-density (ρ=46-166 kg m−3) versus high-density (ρ=170-343 kg m−3, Schweizer and Camponovo, 2001). Great compression of low-density snow cover occurred, and that density change was made to the snow directly underfoot ; the other snow remaining unchanged. As a result, the skier's impact was not spread in low-density snow, but was spread in the crushed snow cover. In this way, it is easier for skiers to influence the snow cover when the density of that is low. However, the skier's zone of influence is limited.View full abstractDownload PDF (2459K) -
Takayuki ABE2015 Volume 77 Issue 1 Pages 67-74
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESS -
Satoshi YANAGI, Akihiko KUBO, Takao KAMEDA, Junʼichi TAMAKI, A.M.M. Sh ...2015 Volume 77 Issue 1 Pages 75-89
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSIn order to clarify the optimum condition for making snow crystal replica by embedding method with light-curing resin (LCR0208), effects of the visual-light intensity and the atmospheric temperature on the curing reaction were examined. Further, the replication accuracy of the replica was investigated. We found that the maximun temperature rise of the resin accompanying the resin curing was less than 2℃ and the time for the curing was less than 10 min when the atmospheric temperature was lower than 0℃ and the light intensity ranged from 2000 to 8000 lux. This result suggests that the melting of the snow crystal does not occur in the replication process provided the atmospheric temperature is lower than −2℃. On the replication accuracy, we found that the replica shrank by 2% linearly and incomplete filling of the resin occured at the bottom of fine grooves. The amount of the incomplete filling of the resin was small enough to not affect for measured profile of the replica by a laser microscope used in this study. Therefore, we found that the original surface structure of snow crystals could be estimated using the replica described above by considering cure shrinkage of LCR0208, which is +2% in length for three directions.View full abstractDownload PDF (3187K)
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