The Japanese Alps collectively refer the Hida Mountains, Kiso Mountains, and Akaishi Mountains, ranging approximately 200 km north to south and 100 km east to west. In terms of span, the Japanese Alps region includes the Ryohaku Mountains to the west and Mt. Fuji, Mt. Yatsugatake, and Mikuni Mountains to the east, making the geographical extent of the region more than 200 km in the east-west direction. The maximum altitude of the Japanese Alps is around 3000 m; however, climatic conditions vary widely because the region lies at the center of Honshu, between the Japan Sea coast and the Pacific coast, and the northern area is known to experience one of the heaviest snowfalls in the world.
It is thought that mountainous areas are particularly sensitive to global-scale environmental changes, such as warming. When attempting to evaluate the effect of a global-scale warming event on regional environmental change in the high-altitude Japanese Alps, we note a lack of high-altitude meteorological observation data. This presents difficulties when evaluating the effects of warming on ecological systems and water resources in mountainous regions.
In this study, we discuss long-term variations of winter temperature, as well as the amount of snowfall and depth of snow cover at twelve observational stations in the Japan Alps region. At eleven sites other than Mt. Fuji, a trend of increasing annual minimum temperature is recognized, which is statistically significant at the 1% significance level. At locations such as Mt. Fuji, which are located at extremely high altitudes, the annual minimum temperature over the last several decades has not been seen to increase or decrease. The trend of decreasing annual cumulative snowfall is statistically significant at the 10% level at Takada, Toyama and Kanazawa stations. At the other eight sites, it is shown that the recent annual cumulative snowfall does not show either an increasing or decreasing trend. The increasing trend of the annual maximum snow depth is statistically significant at the 5% level at Mt. Fuji, whereas a decreasing trend of the annual maximum snow depth is statistically significant at the 10% level at Takada and Kanazawa. At the other nine sites, annual maximum snow depth has not shown a statistically significant change in recent decades.
Recent studies report that the amount of snowfall in Japan will decrease as a result of global warming; however, these studies use data collected at low altitudes. It is, therefore, important to question whether the same theory can be applied to high-altitude mountainous areas. In high-altitude areas of the Japanese Alps region, it is reasonable to expect that a cold atmosphere will be maintained even with global warming, and an increase in evaporated moisture vapor in the air caused by warming on a global scale will increase the amount of snowfall in the region.