Effect of nonlinear tide–surge interaction in the Pearl River Estuary during Typhoon Nida (2016)

Abstract. Storm surge is one of the most significant marine dynamic disasters affecting coastal areas worldwide. A comprehensive study of its mechanisms is vital for improving forecasting capabilities and developing more prevention strategies. In this study, a two-dimensional (2D) numerical model based on the Advanced Circulation Model (ADCIRC) was employed to examine the characteristics of storm surges and the mechanisms of tide–surge interaction in the Pearl River Estuary (PRE) during Typhoon Nida (2016). Three distinct model runs were conducted to differentiate between variations in water levels attributable to astronomical tides, storm surges, and their combined effect. The results indicated that storm tides are primarily modulated by tides through tide–surge interactions. The nonlinear effect of tide–surge interactions is primarily generated by the nonlinear local acceleration term and convection term from the tide–surge interactions in the study area, as derived from mathematical terms. However, in regions of shallow water, such as the northern part of the island of Qi'ao and Shenzhen Bay, they are predominantly governed by the nonlinear wind stress term and the bottom friction term. Furthermore, the variations in the y components of the nonlinear momentum terms are more significant than those in the x components. To investigate the impact of the tidal phase on the storm surge response to Typhoon Nida, the timing of the landfall was altered in order to introduce variations in PRE characteristics. The results demonstrate that the contribution ratio of each nonlinear term remains relatively constant, while the magnitudes exhibit fluctuations contingent on the timing of the landfall. However, further studies on additional typhoon events, especially with onshore winds, are needed, together with a comprehensive consideration of the meteorological processes and mechanisms of tidal-wave propagation inside and outside the estuary. The model system could still be improved in the future.