GEOGRAPHICAL DISTRIBUTION OF TYPHOON RAINS IN JAPAN-FORMATION OF OROGRAPHIC RAIN-BANDS

概要

論文の詳細を見る
During the last 11 years of 1951-61, there were 54 typhoons which attacked the Japanese Archipelago bringing about heavy rains and severe damages.. The geographical distribution of heavy rains in connection with these typhoons were illustrated on about 200 daily isohyetal maps of Japan. And their distribution patterns and hourly changes of rainfall intensities were checked and analyzed. Then, the following four distuibution patterns were identified: 1) Orographic rain-band pattern 2) Frontal rain pattern 3) Coastal rain pattern 4) Scattered rain pattern 1) Orographic rain-band patternA) This was the most frequently occurring and the most characteristic pattern. It occurred on 65% occasions of typhoon rains in Japan (Tab. 1). Amount of areal rainfall for whole Japan brought by one typhoon of this pattern was much larger than those by the other patterns of rains and often exceeed 25×109 tons.B) Locations of rain-bands were restricted geographically to the following 8 regions. The more distinctive ones were designated by asterisk: 1) Bôsô Peninsula (Eastern Japan) 2)* Izu-Tanzawa-Ashio Mts. (Eastern Japan) 3) Akaishi-Kusatsu Mts. (Central Japan) 4) Mikawa-Kiso Mts. (Central Japan) 5)* Kii-Suzuka-Ibuki Mts. (Western Central Japan) 6) Eastern Shikoku-Ôsaka (Western Japan) 7) Western Shikoku (Western Japan) 8)* Eastern Kyûshû (Southern Japan)C) Band structures were mainly constructed on the eastern side of the typhoon path. Therefore the afore-mentioned 8 rain-bands were not always constructed by every typhoon, irrespective of the path of the center. 1) When a large and strong typhoon passed along the western coast of Kyûshû Island, the 8 band structures were observed together frequently.-Fig. 1, TY 5609 & TY 5612. 2) When a typhoon landed on Shikoku Island, the western-most band in Kyûshû was not formed. -TY 5817. 3) When a typhoon hit and traversed central Japan, only eastern band structures appeared remark-ably.-TY 5915.D) At the southern tip of each rain-band, there is a high mountain of more than 1, 000 m in elevation facing to open sea and/or flat lands of its eastern side.E) The axis of each band structure did not always run parallel with the direction of the mountain range starting from the aforementioned southern high mountain. The axis often stretched from SSW to NNE.F) The average width of the rain-bands was rather narrow and only about 30 km, but their maximum length often reached more than 300 km. However, they did not pass beyond the central back-bone mountains of Japan mostly.G) The rainfall of this pattern is not a typical orographic rain along the upslope of a mountain range, as is taught in textbooks of meteorology. Numerical calculations of orographic rainfall at various locations in Eastern Japan were done and the amounts of theoretically expected orographic rains on each cross point of 15 km mesh on the 1: 200, 000 topographic sheets covering the area were evaluated. The calculations were made by different wind directions of each 20° difference and the wind speeds were assumed always to be 20 m/s. The results were plotted on the maps and isohyets were drawn by wind directions. Thus, 18 isohyetal maps of orographic rains in Eastern Japan were constructed and the distribution patterns of orographic rains were illustrated by various wind directions. A similar pattern to the above-mentioned band-type distribution was recongnized with that of orographic rains by prevailling wind of 140° directions as are shown in Figs. 2 & 5. However, the directions of the prevailing wind above the area during rains were about 200° up to at least 10 km and its speeds were about 20 m/s as a shown in Figs. 3, 4, 8 & 10.
The Association of Japanese Geographersの論文

GEOGRAPHICAL DISTRIBUTION OF TYPHOON RAINS IN JAPAN-FORMATION OF OROGRAPHIC RAIN-BANDS

スポンサーリンク

概要

The Association of Japanese Geographers | 論文

スポンサーリンク