偏形樹から推定した卓越風向による本州山地の地域区分

抄録

The author analysed the results of previous studies and her own investigations on the prevailing wind direction estimated by wind-shaped trees (Abies Mariesii, A. Veitchii) in the 16 mountainous regions in the subalpine zone in Central and Northern Honshu, Japan. She studied, at first, the relationship between local wind directions and the running directions of mountain ridges which are classified into N-S, NW-SE, NE-SW and W-E. She also compared the wind directions estimated by wind-shaped trees with the data obtained from the instrumental observations at the climatological station near by.
The results obtained are summarized as follows:
(1) The prevailing wind directions are different regionally in accordance with the directions of mountain ridges. (2) According to the cluster analysis on the combination of wind directions by each direction of mountain ridges in the 16 regions, we can recognize some difinite wind systems with similar characteristics. (3) The regional division was made by these results as shown in Pig. 4. (4) On the basis of the results mentioned above, three climatological regions can be recognized in Central and Northeastern Japan, i.e., (i) The region where the mountain climate of Japan Sea side type prevails (Mt. HachimantaiIwate, Mt. Zao, Mt. Azuma-Adatara-Pandai, Happo-one, Mt. Renge-Eboshi-Mitsudake, Mt. Hakusan, Mt. Kusatsu-shirane). (ii) The region where the mountain climate belonging to the Pacific side type prevails (Ozegahara-nanryo, Mt. tsumata-KumonodairaTaro, Mt. Norikura, Mt. Neko-Azuma, Mt. Kisokoma). (iii) The region where the mountain climates of both types are mixed (Mts. Oku-nikko, Mt. Shiomi-Arakawa, Mts. Okuchichibu. Mt. Yatsu, Mt. Oomine). (5) Roughly speaking, the wind direction distribution estimated by wind-shaped trees on the Japan Sea side of Honshu is similar to the NW flow type of the surface wind system over lowlands. On the other hand, the wind direction distribution estimated by wind-shaped trees on the Pacific side of Honshu is similar to the SW flow type. (6) In addition, the author discussed the results with a few related phenomena: The regional division by climates presented here coincides well with that of the Suzuki's (1962), which was based on the distribution of precipitation in winter. It is, therefore, clear that the wind conditions over the mountainous regions have close relations to precipitation under the influence of winter monsoon.
(7) Shimagare phenomena (stripes of needle trees standing dead on the mountain slopes in the subalpine zone) are distributed on the slopes facing south, southwest and southeast in the subalpine zone in Chubu, . Kanto and Kinki Districts of Honshu. It is noteworthy that all of these areas belong to the mountain climate type on the Pacific side of Japan.