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Volume 77 (2015)
- Issue 6 Pages 475-
- Issue 5 Pages 397-
- Issue 4 Pages 285-
- Issue 3 Pages 233-
- Issue 2 Pages 173-
- Issue 1 Pages 5-
Volume 77, Issue 5
Displaying 1-4 of 4 articles from this issue
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Naoki ANDO, Kenichi UENO2015 Volume 77 Issue 5 Pages 397-410
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSThe top 30 days of two-day rainfall total amounts or snowfall depths from Dec. to Mar. from 1981 to 2014 were counted at 28 AMeDAS stations located in the inland district of Japan as “heavy precipitation days” (HPD) or “heavy snowfall days” (HSD). Long-term trends of HPD/HSD frequency and geographical distribution were examined. In the analysis, limited HPD and HSD appeared in the northern/northwestern area domains under typical winter monsoon pressure patterns; they appeared in other wide areas in cases of passing extratropical cyclones along the south coast of Japan. Occurrence of HPD was not linked to warm/cold winters. It was unusual for HPD and HSD to occur together in the case of a passing extratropical cyclone, as happened on Feb. 14-15, 2014 with extremely heavy snow cover. In this case, water vapor transport distribution in the warm sector of the cyclone showed a unique zonal channel to reach central Japan blocked by a high-pressure system in the northern Pacific, and the strengthened easterly component of the wet air mass intrusion associated with an occluded cyclone provided extremely high precipitation amounts in the inland. The percentage of occlusion increased in cases of cyclones with extreme HPD; however, they were not always accompanied by a blocking anticyclone.View full abstractDownload PDF (4711K) -
Tsutomu IYOBE, Takane MATSUMOTO, Katsuhisa KAWASHIMA, Kaoru IZUMI2015 Volume 77 Issue 5 Pages 411-419
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSThe Kanto-Koshin district had an unusual heavy snowfall on 14-15 February 2014 due to a low pressure passing along the southern coast of Honshu Island. High-density observational data from multiple snow-monitoring network and interviews with local people were used to investigate spatial distribution of snow depth in the Kanto-Koshin district. Analysis of the spatial distribution of snow depth showed that the heavy snow area (over than 100cm depth) extended all over Yamanashi Prefecture and the mountainous area on the border between Yamanashi Prefecture and the western Kanto district. The heaviest snow depth area (over 150cm) occurred locally at the north base of Mount Fuji. Data showed regional differences in the altitudinal dependency of snow depth. In the Kanto region, snow depth uniformly increased with increase of elevation up to about 200m above sea level (A.S.L.), but altitudinal dependency of snow depth over 300m A. S. L. was not obvious. In contrast, altitudinal dependency of Yamanashi and Nagano prefectures showed low gradients and high variation. In comparison with past heavy snowfall events, the exceptional snowfall event of February 14-15 was characterized by the distribution of snow cover more than 50cm even on the western Kanto plain in addition to unusually widespread snowfall centered around Yamanashi Prefecture.View full abstractDownload PDF (3014K) -
Hiroyuki HIRASHIMA, Hiroki MOTOYOSHI, Satoru YAMAGUCHI, Isao KAMIISHI2015 Volume 77 Issue 5 Pages 421-431
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSIn February 2014, the Kanto-Koshin area, which rarely experiences snowfalls, witnessed heavy snowfall and suffered considerable damages. A Snow Disaster Forecasting System was used for these areas. Influences of prediction error of meteorological parameters on the simulated snowpack were mainly investigated since snow depth is rarely measured and cannot be used for the correct data for simulation. The values of both snow depth and snow water equivalent (SWE) obtained by simulation were compared with those obtained by making visual observations. The comparison showed that the simulated values were smaller than the observed values, chiefly because the snowmelt amount was overestimated in the simulation. Estimation of the daily energy balance showed the large influence of solar radiation on snowmelt and the importance of the estimation method of albedo. The natural stability index was estimated for avalanche slopes in the Yamanashi-Prefecture. The snow instability at their slopes was reproduced well. The influence of prediction error by JMA-NHM on the snowpack simulation was also estimated. The data showed that the prediction error of the air temperature affected both the snowmelt amount and the precipitation form, and also that the effect of the prediction error of air temperature was larger than that of the prediction error of precipitation. Results of this study showed that the reduction of prediction error using the observed meteorological data, improvements in the estimation method of the albedo, and clarification of the mechanical process of column-shaped snow crystals are expected to make this system more accurate for non-snowy regions.View full abstractDownload PDF (2329K) -
Hiroki MATSUSHITA, Shinji IKEDA, Kazuya AKIYAMA2015 Volume 77 Issue 5 Pages 433-445
Published: 2015
Released on J-STAGE: March 01, 2023
JOURNAL OPEN ACCESSIn February 2014, because of heavy snowfall in the Kanto-Koshin region, many snow avalanches occurred due to the slip-through phenomena, in which snow slid between the trees and other structures, including the ones installed to prevent snow avalanches and rock-fall. In the Yamanashi prefecture, snowfall intensity of about 4. 0 cm h−1 continued for a period of about 30 hours between February 14-15, and this resulted in accumulation of over 100cm of snow. To examine the snowfall condition in which the snow avalanches occurred, the stability index and hardness of snow on the slopes were estimated using the snowfall intensity and air temperature at that time, and were compared with the favorable conditions for slip-through phenomena identified in a previous study. Our results indicated that the conditions during February 14-15 in the Yamanashi prefecture were favorable for snow avalanches due to slip-through phenomena. In addition, the high elevation areas in the eastern part of Nagano prefecture and the northern part of Gunma prefecture exhibited also the conditions. Therefore, the slipthrough phenomena could have occurred in these regions as well.View full abstractDownload PDF (2026K)
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