| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1987: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1986: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1985: ¥600,000 (Direct Cost: ¥600,000)
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| Research Abstract |
Tidal exchange through a narrow strait was studied by tracking a large number of labeled water particles in a three-dimensional stratified model basin. Theteminology of tidal exchange rate which we used denotes the ability of an innerbasin to trap outer water,
In the barotropic case, the bottom friction induces the two-cell vertical circulation in a latitudinal cross section of the strait, where water upwells along both side-walls and sinks in the central region of the strait during one tidal cycle. The bottom friction produces a large vertical phase lag in the horizontal velocity field around the strait, Therefore, vertical motion of a labeled particle near the strait produces a large Lagrangian-drift which means the necessary condition for tidal exchange.
In the stratification case, tw-cells vertical circulation is confined in the upper layer and water moves in the opposit direction to the barotropic case: Water sinks along the side walls and upwells in the central region of the strait, Straitification reduces vertical velocity and also the exchange rate, The exchanged particles in the upper layer move downwards, and those in the lower layer move upwards, those particles move on a iso-picnal layer far from the strait.
By using the vertical eddy viscosity and diffusivity depending on the horizontal velocity, we studied tidal exchangein the case where vertical mixing destroyed the stratification near the strait, Tidal exchange rate is smaller than that of the stratification case. To represent the yertical mixing in labeled-particle motion, a turbulent velocity must be contained in the operation of tracking particles.
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