In this study, the storm surge processes and characteristics of Tide-Surge Interactions (TSI) induced by the sequential tropical cyclones (TCs) BARIJAT and MANGKHUT (2018) in the Northern South China Sea (NSCS) are investigated using the numerical model. By comparing the impacts of the two TCs, we find that storm surges are significantly influenced by multiple factors. Notably, bays situated on the western side of the cyclone’s landfall point exhibit a double peak pattern in storm surge. In addition, TSI exhibits a pronounced impact across bays affected by the two TCs, with amplitude fluctuations ranging from -0.3 to 0.3 meters and contributing approximately -5% to -20% to the peaks of storm surge. Comparative analysis of TSI variations reveals that tides act as the primary determinant, significantly influencing both the magnitude and period of TSI. Dynamic analysis further highlights that variations in TSI are dominated by barotropic pressure gradient and bottom friction stress. Moreover, TSI affects the frequency of storm surges, introducing high-frequency tidal signals to storm surges and reducing the frequency of storm surges.

storm surge, tide-surge interactions, Northern South China Sea, numerical modeling, mechanism analysis