Tidal resonance in the Gulf of Thailand

Abstract

The Gulf of Thailand is dominated by diurnal tides, which might be taken to indicate that the resonant frequency of the gulf is close to one cycle per day. However, when applied to the gulf, the classic quarter-wavelength resonance theory fails to yield a diurnal resonant frequency. In this study, we first perform a series of numerical experiments showing that the gulf has a strong response near one cycle per day and that the resonance of the South China Sea main area has a critical impact on the resonance of the gulf. In contrast, the Gulf of Thailand has little influence on the resonance of the South China Sea main area. An idealized two-channel model that can reasonably explain the dynamics of the resonance affecting the Gulf of Thailand is then established in this study. We find that the resonant frequency around one cycle per day in the main area of the South China Sea can be explained with the quarter-wavelength resonance theory, and the large-amplitude response at this frequency in the Gulf of Thailand is basically a passive response of the gulf to the increased amplitude of the wave in the southern portion of the main area of the South China Sea.