| Budget Amount *help |
¥3,670,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥270,000)
Fiscal Year 2007: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2006: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
In the rotating annulus experiments, we have studied the topographic beta-effect with the use of a conical bottom and found so far that when the slope of the conical bottom is set 0.4, the wavenumber-2 flow propagates into the stratified layer according to the quasi-geostrophic potential vorticity equation and has a lower drift velocity than in the case of the flat bottom. In this research, we pursued to get more evident beta-effect in the wavenumber-1 and axisymmetric flows because the vertical wave propagations are theoretically known to be stronger as wavenumber is lower. Because it was found very difficult to produce the wavenumber-1 flow, we studied the axisymmetric flow. To measure the vertical dependence of the zonal velocities, here was found a very useful method: a green laser light sheet is projected vertically at the mid-radius of the annulus and video pictures of the vertical sheet are taken from the side. Thus, we could get a dearer beta-effect than in the wavenumber-2 flows. To see directly the vertical flow, furthermore, injecting several drops of uranine solution into the water and projected the halogen light-sheet vertically and meridionally, we could obtain pictures of curved lines of uranine to represent the Lagrangian trajectories of the flow. From the shapes of the observed lines, we could understand that the upward vertical component of the meridional flow is clearly stronger in the conical bottom than in the flat one.
To proceed this study, we visited several institutes such as University of Technology at Eindhoven to give them a talk of our experiments and see their experiments. There we could get useful information, especially that in the technical points, a laser light sheet is available for taking the video pictures of PIV analysis: dye such as ink is very helpful to visualize very slow flows and in the theoretical points, they supported our idea that even in the baroclinic layer the conical bottom would cause the topographic beta-effect.
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