Abstract: Upon analyzing the measured tidal data from the Guanghai Bay, it was observed that there are multiple peaks during the low-high tide periods. Through water level reconstruction analysis using various tidal components, combined with other similar studies and mathematical results, it was found that a significant contributing factor to this phenomenon is the relatively large proportion of quarter-diurnal tidal components, such as M4, in the bay. The interaction among diurnal, semi-diurnal, and quarter-diurnal tidal components leads to this occurrence. By modifying factors such as tidal boundaries, nearshore water depth, and topography, numerical models are constructed to explore the reasons for the large amplitude of M4 tidal component. Results indicate that the primary reason for the large amplitude of M4 tidal component is its overall larger value in this region, the amplitude ratio of M4/M2 approaching the critical condition for multi-peak phenomena. Furthermore, the unique islands and nearshore shallow topography of Guanghai Bay amplify the shallow water tidal components amplitude, resulting in a multi-peak phenomenon at the low-high tide.

Key words: Guanghai Bay, Multi-peak Tides, Harmonic Analysis, Quarter-diurnal Tides, Numerical Simulation