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Volume 62 (2000)
- Issue 6 Pages 515-
- Issue 5 Pages 451-
- Issue 4 Pages 345-
- Issue 3 Pages 185-
- Issue 2 Pages 117-
- Issue 1 Pages 3-
Volume 62, Issue 4
Displaying 1-5 of 5 articles from this issue
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Koji YAMAZAKI2000 Volume 62 Issue 4 Pages 345-354
Published: July 15, 2000
Released on J-STAGE: September 04, 2009
JOURNAL FREE ACCESSThe sea-ice extent of the Sea of Okhotsk varies according to the wintertime atmospheric circulation. On the other hand, the variation of the sea-ice extent influences on atmospheric circulation. The interaction between the wintertime atmospheric circulation and the variation in the sea ice extent of the Sea of Okhotsk is investigated by correlation analyses between the January-February mean atmospheric circulation and the sea ice extent including lag correlations.
The sea ice tends to expand when winds have westerly anomalies over the Sea of Okhotsk and the low-altitude temperature is low at the upstream side of the Sea. From the atmospheric conditions around the Sea of Okhotsk and the sea ice extent in early January, a multiple regression equation can predict the January-February mean sea-ice extent with good accuracy. A tendency for warm climate over Japan south of Tohoku is seen when the sea-ice extent becomes large. In this relationship, the correlation becomes better when the sea-ice extent leads the temperature. This suggests influence of sea ice on climate in Japan. The sea-ice extent has correlations with the hemispheric-scale atmospheric circulation such as the North Atlantic Oscillation/Arctic Oscillation. A correlation with the Western Pacific pattern is also found.
In order to extract the signal of the influence of the sea ice on the atmospheric circulation, we define a 4-point index for 500hPa geopotential height. The points of the index are located over Japan, Kamchatka, Alaska and North America. When the sea ice and the index are simultaneous or sea ice lags the index, the correlation becomes maximum. Then, a 2-point index which consists only of the Alaska and North America points is defined. For the 2-point index, the maximum correlation occurs when the sea ice leads the atmosphere by one month. Considering this lag, the variation in the sea ice extent of the Sea of Okhotsk affects the atmospheric circulation over the Alaska and North America.View full abstractDownload PDF (1922K) -
Hiroki MATSUSHITA, Yoshihiro GONNOKAMI2000 Volume 62 Issue 4 Pages 355-365
Published: July 15, 2000
Released on J-STAGE: September 04, 2009
JOURNAL FREE ACCESSTo examine the climatological features of glaze occurrence, in Nagano prefecture, where there have been many reports on the glaze, glaze occurrence days were defined and their areal distribution was statistically analyzed.
Glaze forms on exposed objects at the ground by the freezing of supercooled water droplets, in a kind of ice accretion. For glaze to occur, in general, two meteorological conditions must be satisfied. One is the existence of a warm air layer (air temperature above 0°C) in the upper air, for melting of dry snowflakes into rain drops; the other is the existence of a cold air layer (air temperature below 0°C) near the ground, for cooling of rain drops into supercooled water droplets. This is called a “melting ice process”. Although glaze also occurs at air temperatures below 0°C at all levels (no warm air layer), in what is called a “supercooled warm rain process”, only the term “melting ice process” is used in this study.
Aerological data were used to examine the warm air layer in the upper air, AMeDAS data were used to examine the cold air layer near the ground and precipitation, during 20 winter seasons (November 1979-April 1999). A day that satisfied these two meteorological conditions is defined as a glaze occurrence day. As a result, there are frequent peaks of glaze occurrence in December and March. The number of days with glaze has been decreasing in the past 6 years.
Next, a mesh map of annual mean number of days with glaze was obtained by multiple regression analysis using a factors that represent a topographical features as independent variables. The mesh map shows a high number of days with glaze in central and eastern Nagano prefecture. In particular, because of the close relationship between the annual mean number of days with glaze and the altitude, a high number of days with glaze were estimated to occur mountain areas and highlands, while a low number of days with glaze occurred in low altitude areas of northern and southern Nagano prefecture.View full abstractDownload PDF (4991K) -
Shigehiro IIKURA, Katsuhisa KAWASHIMA, Toru ENDO, Toshishige FUJII2000 Volume 62 Issue 4 Pages 367-374
Published: July 15, 2000
Released on J-STAGE: September 04, 2009
JOURNAL FREE ACCESSTo improve the safety of railways in snowy regions, a new system for detecting avalanches has been designed and developed. This system consists of a detecting unit, a signal conversion device and a display device. The detecting unit installed on a slope subject to avalanches detects vibrations due to the avalanche impact with a built-in vibration sensor. Operating tests of the new system were carried out using an artificial avalanche chute 20 m in length. The tests revealed that the system can not only detect the occurrences of avalanche but also judge the scale of the avalanche. In addition, field tests in Shiaidani valley in Kurobe Gorge showed that the system is of much practical use, because it could accurately detect the occurrence of natural powder snow avalanches throughout the winter season of 1998/99.View full abstractDownload PDF (6299K) -
Kenichi UENO, Hiroyuki OHNO, Kotaro YOKOYAMA, Yasuhiro KOMINAMI, Masah ...2000 Volume 62 Issue 4 Pages 375-383
Published: July 15, 2000
Released on J-STAGE: September 04, 2009
JOURNAL FREE ACCESSOn March 30, 2000, domestic science workshop about the solid precipitation measurement was held at the Institute of Low Temperature Science in the Hokkaido University. Observation methods, result of the intercomparison, and issues of the data correction for water cycle studies are reported by seven presentations. Major discussions are such as, development of new sensor to observe snow particle for shallow snowfall, heating of wind shield to prevent heavy snow cap, evaluation of drifting snow in windy arctic regions, and issues for precipitation intercomparison in the Tibetan Plateau, Siberia, and Hokkaido in Japan.View full abstractDownload PDF (4821K) -
2000 Volume 62 Issue 4 Pages 448
Published: 2000
Released on J-STAGE: September 04, 2009
JOURNAL FREE ACCESSDownload PDF (80K)
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