On the Visibility on Mt. Ibukisan

Abstract

Ibukisan (1377m above the sea level) is an isolated mount in Central Japan and is one of the important places of the air way. Hence the measurement of visibility from Mt. Ibukisan is very important. Visibility on the high mountain is naturally better than those at the lower places and the former has special character. We investigated the visibility on Mt. Ibukisan from 1925 to 1934 at 10^h, and 14^h every day. We chose 9 objects, Mt. Hakusan, Ontake, Kinkasan, Hirasan, River Ibi, Island Oki and Bay of Tsuruga, locating at different distances and in different directions.
Generally the visibility is best in November and worst in August. But as to the high mountain, it is best in November and worst in June. Generally speaking, visibility is better in the morning than in the afte noon.
Visibility is the best in NE wards (mountainous districts), the next is in S wards (lower mountainous lands) and the worst is in NW wards (Bay of Tsuruga).
The most cases of the best visibility were occured when the movable high pressure is over Central Japan, and those of the worst visibility were also occured when the stationary high pressure is over Central Japan.