Abstract
The weather and climate of two mountains were estimated using the AMeDAS, aerological data, etc. A cold front passed over on the Sea of Japan on October 24, 2015, bringing fog with severe wind and soft rime on trees to Mount Kusatsu-Shirane (Mt. K) at 2171 m on October 25 and fine soft rime with strong winds to Mount Azumaya (Mt. A) at 2354 m on October 26. The minimum and maximum air temperatures were estimated to be -5.1°C and 1.9°C, respectively, on Mt. K on October 25 and -4.7°C and 8.3°C on Mt. A on October 26. The minimum relative humidity was estimated to be 18% at both locations, and was observed to be 3% on Mt. Fuji on October 25 and 26. The maximum wind speed and maximum instantaneous wind speed were estimated to be 16.5 m/s and 35.2 m/s, respectively, with northern winds on Mt. K on October 25, and 10.1 m/s and 21.9 m/s with north-western winds at Mt. A on October 26. On October 25 and 26, it was estimated that the airstream from the Sea of Japan converged at the Mikuni Mountains and that the wind primarily descended from mountain passes on the east side of the Mikuni Mountains, arriving as an isthmus wind in the Minakami-Numata valley, then passed through Maebashi to the Kanto Plains, arriving as a local wind Karrakaze. A higher-speed wind with the opposite south direction blew at Minakami, and a high-speed wind of the original north direction passed over the Mikuni Mountains. The air temperature of the wide stream from the Sea of Japan decreased with elevation at the Mikuni Mountains and, after the airstream passed over the mountains, it blew into the Kanto Plains as a typical bora wind with low air temperature.
This paper introduces a simple estimation procedure based on an analysis of the alpine weather and climate at Mounts Kusatsu-Shirane and Azumaya.
