Study on the bivariate distribution characteristics of extreme wave height and wave direction under different weather systems

Significant wave height and wave direction are key parameters in ocean dynamics. Investigating their bivariate distribution characteristics under extreme conditions caused by different weather systems is of great significance for practical applications in ocean engineering. The present study analyzes these characteristics in the southern Yellow Sea and the northern East China Sea. Due to the clear trajectory records, extreme waves driven by tropical cyclones are identified through trajectory tracking and time matching. Due to the significant characteristics of the atmospheric circulation pattern, extreme waves driven by other weather systems are identified by the K-means clustering method. The results show that two types of extreme waves are derived, and the weather pattern characteristics indicate that their driving weather systems are cold surges and extratropical cyclones. By analyzing the temporal and directional characteristics of these waves, significant distribution differences are detected, confirming the rationality and necessity of the classification. For instance, the bivariate distribution characteristics of extreme wave height and wave direction under different weather systems may vary significantly. The main direction sector of extreme waves driven by the same weather system in the study region [e.g., the sector (240°–330°) of extreme waves driven by cold surges] can be derived, providing powerful support for the directional protection of ocean engineering.