AbstractAmong all the phenomena in the ocean, tide is the one with regular eustatic movement, which is closely linked to human activities. When tidal waves propagate towards the nearshore shallow water areas, the waveform deforms because of nonlinear interactions. The shallow water tidal constitutes, including overtides and compound tides are thus necessarily introduced in order to describe the deformed tidal waveform.
Considering the northwest European continental shelf, tidal elevations are significantly affected by shallow water effects. The maximum amplitudes of quarter-diurnal tides M4 and MS4 can reach up to 0.25m and 0.21m high, respectively. These quantities are larger than those of most diurnal tides there. It could be seen that the shallow water tidal constituents ought to be taken into consideration for tidal elevation prediction. In present study, Princeton Ocean Model (POM) is adopted to simulate higher harmonics and long period tides in shallow waters in the Taiwan Strait. Computed tidal elevation amplitudes are compared with the observed data of shore-based tidal gauges on the western coast of Taiwan. Furthermore, tidal constituents of higher harmonics and long period tides are used to illustrate the magnitude and spatial variability over the Taiwan Strait.
The results of simulations show that the Taiwan Bank, which locates in the southwest shallow water region of Taiwan Strait, induces significantly the spatial variations of amplitudes of third-diurnal, quarter-diurnal and sixth-diurnal tides. The spatial distribution of amplitudes of quarter-diurnal and sixth-diurnal tides is similar to the resonance of standing waves. This phenomenon can be confirmed by both theoretical derivation and the analyses of observed data. The fifth-diurnal constituent features the smallest amplitude in present study. The maximum amplitude of fifth-diurnal constituent occurs from TamShui to Hsinchu, whereas the minimun amplitude occurs in south of Kaoshiung. The spatial distribution of amplitudes of fifth-diurnal constituent is consistent with field data observed from the tidal gauges on the western coastline of Taiwan. In addition, the result of simulations also demonstrate the facts that the amplitude variations of higher harmonics and long period tides become significant in cases if the water depth is less than 120m. It is the water depth when tidal waves propagate from deep Pacific Ocean towards the continental shelves of the eastern Taiwan.
|Date of Award||2004|
|Supervisor||高 家俊 (Supervisor) & Zsu-Hsin Chuang (Supervisor)|