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Volume 83 (2021)
- Issue 6 Pages 547-
- Issue 5 Pages 465-
- Issue 4 Pages 385-
- Issue 3 Pages 249-
- Issue 2 Pages 143-
- Issue 1 Pages 3-
Volume 83, Issue 3
Displaying 1-7 of 7 articles from this issue
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Takahiro CHIBA, EVGENY Isenko, Kohei NISHIDA, Yoshihiko SAITO, Rina MI ...2021 Volume 83 Issue 3 Pages 249-258
Published: 2021
Released on J-STAGE: December 17, 2021
JOURNAL OPEN ACCESSIn this study, to clarify the formation mechanism of snow cornice on the eaves of flat roofs, the relationship between the behavior of snow particles near the eaves and the formation of snow cornice was examined based on wind tunnel tests for flat roofs with parapets. The tests were conducted on using wind tunnel facility owned by Hokkaido University of Science, and a wooden prototype of roof with parapet. The behavior of snow particles was photographed with a high-speed camera, and PTV analysis was performed using these images. In addition, the reproduction test of snow cornice was conducted by continuously suppling natural snow in the wind tunnel. According to the results of PTV analysis, it was clarified that the formation and growth of the snow cornice was due to the movement of snow particles in the wind direction. In the reproduction test of snow cornice, the snowdrift occurred on the eaves of the specimen at wind speed of 3 m/s. Furthermore, the cornice overhanging approximately 0.15m from the eaves was formed. According to the results of analyzing the relationship between the PTV analysis and the cornice reproduction test, the spatial concentration of snow particles increased as the wind speed decreased. The main factor for the formation and growth of the cornice due to snowdrifts on the eaves was that the spatial concentration of snow particles reached saturation.View full abstractDownload PDF (2612K) -
Satoka MASUZAWA, Satoshi OMIYA, Tsubasa OKAZE, Hirofumi NIIYA2021 Volume 83 Issue 3 Pages 259-273
Published: 2021
Released on J-STAGE: December 17, 2021
JOURNAL OPEN ACCESSTo elucidate vertical structures of blowing snow with the snowfall, we acquired blowing snow events, which reached equilibrium, from observational data of two months. Estimation of the snowfall frequency in each event was based on snow particle diameters that were greater than 400μm, which were assumed as snowfall particles in this study. Wind profiles were expressed as logarithmic functions of the height; additionally, the roughness length during high snowfall frequency was smaller than during low snowfall frequency at the equivalent friction velocity. The snow-drift flux during low snowfall frequency decreased with increasing height and exhibited uniform distribution at high snowfall frequency. Moreover, the friction velocity dependency of snow-drift flux was confirmed, but the variation was high during high snowfall frequency. The snow-drift flux of during snow particles with less than 200μm diameter decreased with increasing height, whereas that of snowfall particles was vertically uniform. Therefore, the change in the vertical distribution of the snow-drift flux influenced by snowfall frequency was quantitatively explained through the role of snowfall particles to the total snow-drift flux.View full abstractDownload PDF (3631K) -
Seika TANJI, Masaru INATSU, Sho KAWAZOE, Yousuke SATO2021 Volume 83 Issue 3 Pages 275-284
Published: 2021
Released on J-STAGE: December 17, 2021
JOURNAL OPEN ACCESSIn this study, we estimated the visibility reduction due to blowing snow and created a blowing snow map of Hokkaido in 2017/2018 winter (December-February) with 1km resolution data. We also analyzed mean sea level pressure (MSLP) anomalies in the winter using the self-organizing map (SOM) in order to examine synoptic characteristics which resulted in the blowing snow conditions. We used a 1km dynamically downscaled data to make the blowing snow map and 60-year JRA-55 data to produce the SOM. Blowing snow developed frequently in the Ishikari plain and along the coastline of the Sea of Japan. In the SOM analysis, MSLP anomalies were classified into three patterns, positive pressure anomalies over Japan, negative pressure anomalies over central Japan or the Sea of Japan, and negative pressure anomalies east or southeast of Hokkaido. The third pattern resulted in the highest frequency of blowing snow events over Hokkaido.View full abstractDownload PDF (2602K) -
Konosuke SUGIURA, Seiya OOI, Masaki NEMOTO, Kenji KOSUGI2021 Volume 83 Issue 3 Pages 285-297
Published: 2021
Released on J-STAGE: December 17, 2021
JOURNAL OPEN ACCESSAs the wind becomes strong, snow particles repeat an impact/rebound/ejection on the snow surface, and blowing snow develops three-dimensionally. In this study, we investigate how blowing snow develops horizontally perpendicular to the wind direction during the splash process on a hard snow surface using a low-temperature wind tunnel. The obtained results showed that as the wind velocity increased from 6.0ms−1 to 8.0ms−1, the horizontal impact velocity increased, and the impact angle approached the wind direction due to the air resistance acting on the snow particles. The mean horizontal plane rebound velocity was 0.66 times that of the impact velocity. The ratio of the horizontal plane rebound velocity to the horizontal plane impact velocity of individual snow particles was widely distributed, ranging approximately from 0.2 to 1. Besides, large rebound snow particles were experimentally observed in the direction perpendicular to the horizontal plane wind direction, which had not been captured by previous observations from a vertical cross-section. The distribution of the horizontal plane rebound angle was explained by the geometric relationship of the collision. These snow particles are responsible for development horizontally perpendicular to the wind direction. In addition, as the wind velocity increased, the percentage of the blowing snow mass flux in the vertical and perpendicular directions to the wind changed slightly. The development in the direction perpendicular to the wind direction may have been weaker because the number of collisions with the snow surface decreased as the wind speed increased.View full abstractDownload PDF (1802K) -
Masaru MATSUZAWA, Satoshi OMIYA2021 Volume 83 Issue 3 Pages 299-305
Published: 2021
Released on J-STAGE: December 17, 2021
JOURNAL OPEN ACCESSThe authors provide information on visibility prediction of blowing snow on the internet. In this system, the average visibility value per hour is estimated based on the hourly wind speed, temperature, and precipitation intensity provided by the Japan Meteorological Agency. However, because the fluctuations of a blowing snow are intense, there is a large difference between the average visibility and the instantaneous visibility. Therefore, understanding the difference is important when a driver is to make a decision related to traffic behavior. In this study, the authors investigated the relation between average visibility and instantaneous visibility. First, the mass flux of snow is measured using an SPC (Snow Particle Counter), and the resultant values were converted into visibility data. Using the data, the author analyzed the relationship between hourly average visibility Vh and instantaneous visibility Vi, and found that the maximum value of instantaneous visibility is about 30 times Vh, and the minimum value is about 0.2 times Vh. In addition, the visibility fluctuation rate F, defined as the ratio of the standard deviation σ of logVi to the hourly average value of logVi, was 12-15 %.View full abstractDownload PDF (834K) -
[in Japanese]2021 Volume 83 Issue 3 Pages 307-315
Published: 2021
Released on J-STAGE: December 17, 2021
JOURNAL OPEN ACCESS -
Yoshihiko SAITO, Masaya OTSUKI, Kouichi NISHIMURA, Masaru MATSUZAWA2021 Volume 83 Issue 3 Pages 317-328
Published: 2021
Released on J-STAGE: December 17, 2021
JOURNAL OPEN ACCESS
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