An analytical study on M<sub>2</sub> tidal wave in the Taiwan Strait with the
extended Taylor's method
Abstract. The tides in the Taiwan Strait (TS) are featured by large M2 amplitudes. The extended Taylor's method is employed in this study to provide an analytical model for the M2 tide in the TS. The strait is idealized as a rectangular basin with a uniform depth, but the Coriolis and friction forces are retained in the governing equations. The observed tides at the northern and southern openings are used as open boundary conditions. The obtained analytical solution, which consists of a stronger southward propagating Kelvin wave, a weaker northward propagating Kelvin wave, and two families of Poincaré modes trapped at the northern and southern openings, agrees well with the observations in the strait. The superposition of two Kelvin waves can basically represent the observed tidal pattern, including an anti-nodal band in the central strait, and the cross-strait asymmetry (greater amplitudes in the west and smaller in the east) of the anti-nodal band. The superposition of Poincaré modes can further improve the model result in that the cross-strait asymmetry can be better reproduced. In order to explore the formation mechanism of the northward propagating wave in the TS three experiments are carried out, including the deep basin south of the strait. The results show that the southward incident wave can be reflected to form a northward wave by the abruptly deepened topography south of the strait, but the reflected wave is slightly weaker than the northward wave obtained from above analytical solution, in which the southern open boundary condition is specified with observations. The forcing at the Luzon Strait can strengthen the northward Kelvin wave in the TS, and thus is of secondary importance to the M2 tide in the TS.