South Coast Of Japan Research Articles

Sea level variations along the south coast of Japan and the large meander in the Kuroshio

Sea level variations from 1974 through 1976 at 9 stations on the south coast of Japan (from west to east, Aburatsu, Tosa-shimizu, Muroto-misaki, Kushimoto, Uragami, Owase, Toba, Maisaka and Omaezaki) were analysed in relation to the large meander in the Kuroshio. From May to July in 1975, a small maximum in sea level variation was observed at every station west of Cape Shionomisaki from Aburatsu to Kushimoto. It propagated eastward along with the eastward propagation of a small meander in the Kuroshio until it reached Kushimoto, when the sea levels at Uragami and Owase started to rise sharply. This remarkable rise appeared at all stations in August when a large meander in the Kuroshio was established. The mean sea level at the stations east of Cape Shionomisaki from Uragami to Omaezaki rose by about 10 cm. The difference in sea level variations between the regions east and west of Cape Shionomisaki, which had been present before the rise, disappeared. A similar characteristic of sea level variation was also found in the generation stage of the large meander in 1959. The sea level variations along the south coast of Japan indicate that, prior to the generation of the large meander, the small meander in the Kuroshio was generated southeast of Kyushu and propagated eastward and that, just when this meander reached off Cape Shionomisaki, a large scale oceanic event covering over the whole region of the south coast of Japan occurred. This large scale event seems to be one of the necessary conditions for the generation of the large meander in the Kuroshio off Enshu-nada.

Barotropic disturbances caused by a point storm in aβ-plane ocean

Barotropic equation for vorticity balance in theβ-plane is solved for a volume transport stream function with a northward moving wind stress torque concentrated at a point (tweak). Asymptotic techniques are applied to the solution expressed by Fourier type integrals. In the front zone (northern half from the tweak) the stream function behaves asO(¦X¦−5) whereX is a scaled eastward coordinate. In the wake, the stream function behaves asO(¦X¦−1/2) within a wedge bounded by the westward axis and a line directed SSE approximately, but behaves asO(¦X¦−5) in the rest of the half plane. On these boundaries it behaves asO(¦X¦−5/2) andO(¦X¦−1/3), respectively. East-west asymmetry is a result of asymmetry in zonal propagation of the planetary waves, which also cause the wavy pattern of the streamline in the western half of the wake. Friction is most effective in decreasing the stream function in the south to SSW sector and least effective to the west. Effect of divergence changes the wave pattern in the western half of the wake but does not change magnitude of the stream function. It is speculated that abnormal changes in daily mean sea levels observed in 1965 to 1971 along the south coast of Japan may be caused by the wake effect of moving typhoons east off Japan.

1971年9月の本州南岸の異常潮位について-第3部.本州南岸に沿う陸だな上の異常潮位についての数値実験-

1971年9月の本州南岸の異常潮位について-第3部.本州南岸に沿う陸だな上の異常潮位についての数値実験-

1971年9月の本州南岸の異常潮位について-序論-

1971年9月の本州南岸の異常潮位について-序論-

On the Variation of the Kuroshio

The review on the variation of the Kuroshio extending from several hours to ten years is described here. We have had no clear understandings on the mechanisms of occurrence of large and comparatively stable meander off Kisyu-Ensyu Nada. It is known, at present, that the selected several small meanders in spring off the east coast of Kyusyu progress towards east along the south coasts of Shikoku and Kii Peninsular and stop its advance off Ensyu Nada and become large. This large meander is always accompanied, inside of it, with the ascending cold intermediate water in the Pacific. We cannot fully understand the mechanisms of occurrence and continuation of this large meander without knowledges of the deep and bottom current based on the direct measurement and the long-term variation in the atmosphere over the Pacific especially subtropical western Pacific.There exist middle and small scale meanders which progress easterly almost every time except the period of large stable meander off Kisyu-Ensyu Nada. The Kuroshio which flows along the south coast of Japan might exist in the duration only about 1/4-1/6 of total period after the World War II. Therefore the paths of large scale meander off Kisyu-Ensyu Nada and Middle and small scale meanders traveling easterly must not be considered abnormal. The very short-period fluctuations, one or half a day, of the velocity and direction of the Kuroshio were observed only by several systematic programmes with several vessels in Japan. From these simultaneous observations, comparatively large variations of velocity of the Kuroshio which may mask the amplitude of long-period variation of the Kuroshio were found. The observations of detailed pattern and direction of propagation of disturbed wave will be necessary to get the causes of these variations.

1971年9月の本州南岸の異常潮位について -第2部.東京湾における異常潮位-統計的調査-

"1971年9月異常潮位"で問題にされた,広範囲のしかも長期間にわたった現象に着目して東京湾における過去事例の抽出を試みた。この際,日平均潮位偏差に対しさらに31日移動平均よりの偏差を求め,この偏差の度数分布の標準偏差を単位に用いて潮位を測り,湾における浅水効果の除去を行なった。異常潮位は東京湾においては年に1-2回程度生じ,湾全体にわたって標準偏差の2-3倍程度の変動が少なくとも3日間持続するものであることが,潮位変動の解析から分った。異常潮位時の気象・海象の特性を平年のそれと比較することにより抽出した。その結果,おだやかな気象条件の下で生じ,波浮(大島)の海水温と関係が深いことが分った。すなわち高(低)水温時に潮位上昇(下降)が対応し,しかもこの時弱風ではあるが,海風(南風系)が高水温時の潮位上昇を,陸風(北風系)が低水温時の水位下降をそれぞれ助長していることが判った。

1971年9月の本州南岸の異常潮位について-第1部.1週間以上持続する異常な潮位上昇について-

西日本の太平洋岸では異常な潮位上昇が1週間以上も継続する現象がしばしば現れる。これが初秋の頃の大潮と重なって現れると低い海岸では浸水の被害を生ずることがある。この論文では1964-1968年の間に起った8例の異常潮位上昇,および1971年9月の例について,気象および海象と関係づけながらその性質を調べる。この潮位上昇は気象擾乱の直接的効果によるいわゆる高潮ではない。ある気象条件によって誘起された黒潮の流れの場の変動が潮位変化を起したものと考えられる。またこの潮位上昇は西に向ってゆっくり伝播するが,これはContinental Shelf Waveを考えると説明がつきそうである。

接岸航行中の位置記入作業及び離岸距離について(日本航海学会第26回講演会)

This paper describes the subjects as follows ; 1) Time interval of cross bearing in night and day time. 2) Critical distance from shore. 3) Deviation to be addmitted on coasting along South coast of Japan.

一月より四月に亙る那覇の氣壓傾度と高知の降雨、氣温、日照との相關

一月より四月に亙る那覇の氣壓傾度と高知の降雨、氣温、日照との相關

The Recent Seismological Disturbances in South Japan

IN the accompanying figure is reproduced, on about half the original scale, an interesting seismogram received from Prof. A. Belar, of Laibach, through the courtesy of the foreign editor of the Daily Mail. The earthquake in question occurred on the morning of January 12, and was recorded by a Galitzin seismograph with electromagnetic damping. The times indicated on the diagram are referred to mean time of central Europe, which is one hour in advance of Greenwich time. In a second letter, Prof. Belar gives ioh. 40m. 35s. as the time of arrival at Laibach of the first preliminary tremors, and he estimates that the earthquake occurred at 6h. 29m. 2s., p.m., Japan time.1 According to information recentlv received from Japan, 337 earthquakes occurred in the south of the country on January 12, the strongest of all being recorded at Nagasaki at 6h. 29m. 27s. The coincidence is so close as to justify Prof, Belar's conclusion that the earthquake recorded at Laibach originated near the south coast of Japan. That the earthquake was of considerable strength is evident from an account by the Rev. A. C. Hutchin-son, of Kagoshima, which appeared in The Times for February 6. “The earth,” he says, “seemed to leap convulsively upwards. The quaking was so great for two minutes that it was difficult to stand.”