Behavior of fresh water injected at the surface of a uniformly rotating ocean |
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| Authors: | Yoshiteru Kitamura Yutaka Nagata |
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| Institution: | 1. Geophysical Institute, University of Tokyo, Bunkyo-ku, 113, Tokyo, Japan
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| Abstract: | The behavior of low density fresh water injected at the surface of a uniformly rotating saline water was investigated on the basis of a tank experiment. The injected water mass shows a clockwise circulation and grows gradually with an axisymmetric convex shape, until it breaks into two vortices at a critical size. An experimental formula for the change of radius of the water mass with time for the axisymmetric stage is obtained. It is shown that within our experimental range of values the radius of the water mass increases almost in proportion tot 1/2, wheret is the elapse time, while the inviscid theory indicates that the radius should increase in proportion tot 1/4. The dependence of the radius on elapse time is essential for forecasting the extent of discharged waters. The position of the maximum azimuthal velocity is fixed at \(V = - ge^{ - a^2 q^2 } \) within our experimental range of values wherer is the radial coordinate,f the Coriolis parameter,v the viscosity coefficient andQ the flow rate of injection, respectively. This radius corresponds to the radial scale derived by Gillet al. (1979). The steadiness of the position of the maximum azimuthal velocity may be essential in partition of the water mass into inner and outer regions and in the understanding the derived experimental formula. The critical radius for breaking is also investigated. The radius is shown to be independent ofQ and to be almost proportional to (Δ ρ / ρ )1/2 f -1 whereρ is the density of the saline water andΔρ the density difference between the saline and injected waters. Even after the water supply is cut off in the axisymmetric stage, the radius of the water mass increases at almost the same rate as before, while its thickness decreases. The behavior after supply cut-off is discussed in the Appendix. |
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