Modeling and characterization of wave spectra in intermediate water depths under typhoon conditions in the South China Sea

This study investigates the modeling and characterization of typhoon-induced wave spectra in intermediate water depths of the South China Sea, a region critical for offshore energy development. By analyzing field measurements from three typhoon events (Ewiniar, Sontinh, Bebinca), we compare the performance of three bimodal wave spectral models: the GH98, APA19, and L22 model. Results show that the L22 model outperforms the others in fitting both bimodal and unimodal spectra, exhibiting lower significant wave height ( H s ) errors and better agreement with observed spectral characteristics. The temporal evolution of wave spectra reveals distinct phases: wind-sea dominance prior to typhoon formation, swell dominance post-formation, a bimodal structure during typhoon intensification and passage, and a return to swell dominance after dissipation. Notably, bimodal spectra persist during peak typhoon intensity, challenging the prevailing assumption of unimodal spectral dominance during extreme events. The study also establishes a refined empirical relationship between spectral width ( B ) and peak enhancement factor ( γ ) for bimodal spectra, thereby improving spectral parameterization accuracy. These findings provide valuable insights for wave spectral modeling in typhoon-prone regions, with direct implications for marine engineering design and risk assessment in the South China Sea. The L22 model's robustness and adaptability make it a reliable tool for predicting wave field evolution under extreme weather conditions. • Development of a well-fitted model for typhoon-induced wave spectra in intermediate water depths in the South China Sea. • Comprehensive characterization of the spatiotemporal evolution of bimodal spectra across different typhoon stages. • A refined and more accurate relationship between the spectral width ( B ) and spectral peak factor ( γ ) for bimodal spectra.