Variation of the Kuroshio south of Japan |
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| Authors: | Hideo Nitani |
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| Institution: | 1. Hydrographic Department, Maritime Safety Agency, Tsukiji 5 Cho-me Chuo-ku, 104, Tokyo, Japan
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| Abstract: | The variations of the velocity and path of the Kuroshio are investigated by using the data obtained after the World War II. The time scales of these variations are classified into three categories,i.e. long-, medium- and short-terms. Period of the long-term variations seems to be about 7 to 9 years. Large meanders of the Kuroshio off Enshu-nada in 1953–1955 and 1959–1962 are accompanied with the low mean velocity of the Kuroshio. These large meanders are explained as a stationary Rossby wave by applying the equation for the phase velocity of the barotropic Rossby wave with the disturbance of finite width. To obtain the above conclusion, it is assumed that the Kuroshio extends down to the depth of 2,300 db and that the east component of the over-all mean velocity of the meandering Kuroshio should be substituted for the velocity of the eastward basic current in the above equation. As for the medium-term variation of the Kuroshio, there seems to exist variations in the velocity with the periods of 4, 6, 8 and 12 months and those in the position of the Kuroshio axis with the periods of 8 and 12 months. These meanders of the Kuroshio progress towards east with the mean phase velocity of about 5 miles a day, which is nearly the same as the calculated mean phase velocity of a progressive Rossby wave. |
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