Modeling of extreme waves in the South China Sea under the influence of tropical cyclones: long-term statistical perspective in Xisha reef islands

Comprehensive research on the distribution of extreme waves in the South China Sea (SCS), particularly within the proximity of reef islands is notably scarce. This study investigates the extreme wave distributions in the SCS and the vicinity of the Xisha reef islands. Focusing on the statistical influence of tropical cyclones over a long period on extreme waves, a total of 242 TCs in SCS and 170 TCs in the vicinity of Xisha reef islands are considered and analyzed. Tests have been conducted to verify the suitability of the FVCOM modeling framework for hydrodynamic simulations in the reef islands, and then the annual/seasonal averaged and return level wave distributions from 2000 to 2020 were analyzed using the numerically simulated data based on this model. A wave hazard risk index and a TC impact factor are introduced to statistically assess TC effects on extreme wave distribution and hazard risks. The results reveal a significant increase in extreme wave height in the SCS and the Xisha reef islands under the influence of TC, with a considerable diversion of wave direction as well as the location of the shadow zone under the extreme conditions in the Xisha reef islands. Representative shallow water locations near the Xisha reef islands are further discussed to assess the TC influences on local extreme waves. The results of this study could guide engineering site selection and design, TC disaster prevention, and reef island protection in the SCS.