| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
The property of wave propagation in the Pacific ocean was studied by the use of altimeter data obtained by the satellite TOPEX/POSEIDON.The eastward propagating Kelvin waves are detected in the equatorial area, and the westward baroclinic Rossby waves in the middle latitude. The presence of these waves suggests the possibility of the ocean prediction such as the weather prediction in the meteorology from the regularity of the waves. The first, the data assimilation with nudging method was carried out to investigate the possibility of the prediction. The numerical simulation could represent the generation process of the waves owing to the wind forcing, but does not the propagation speed. As time advances, the results deviates from the observation. However, the wave is continuing to be adjusted while propagating after the assimilation, the results are greatly improved.
Secondly, the Kelvin wave excited by an intraseasonal wind forcing with a 40-day period over the western Pacific ocean wa
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s simulated using an ocean general circulation model, and was investigated by the use of spectral analysys. The amplitude of the temperature has two peaks north and south of the equator at the depth of the thermocline, and the amplitude of zonal velocity also has two peaks on the equator up and down the thermocline. Further, it was put in question why this wave, which appears to be transient rather than modelike, always propagates with a phase velocity having a special value of about 3m/s. The vertical one-dimensional forcing problem in the infinitely deep ocean was studies to focus on the transiency, where the external forcing of up and down motions moving eastward is imposed at the surface and the reflection from the bottom is inhibited. The wave response to the forcing with a speed of about 3m/s has a large amplitude, i.e. quasi-resonance occurs. In this case, the thermocline plays the role of a reflector, and the upper ocean between the sea surface and the thermocline behaves as a duct. Here, the special value of the wave velocity is interpreted as a resonance condition. It was found that the wave damps in consequence of leaking energy downward, and the damping rate depends on the period of the wave. Less
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