Joint probability analysis of significant wave height and wind speed under extreme weather conditions

The joint probability analysis of marine variables is essential for the design of ocean engineering structures. The present study conducts such an analysis for extreme significant wave height and wind speed in the Bohai Sea, the Yellow Sea, the East China Sea, and the northern South China Sea. The results indicate that the lower tail dependence characteristics in the southern Yellow Sea and the northern East China Sea are significantly different from those in other regions. By studying the driving relationship between wind and waves and the impact of swell, it is found that the latter may be an important factor leading to this regional difference, which weakens the lower tail dependence. Based on the joint distribution, return levels of the OR and AND return periods are derived. Due to the consideration of the wider risk domain, the former is greater than the latter. Considering that some ocean engineering structures are sensitive to a specific marine variable, return levels of the conditional return period are further studied. Compared with the OR return period, the return levels are significantly reduced. Therefore, it is important to determine the appropriate return level based on the structural characteristics and requirements of ocean engineering.