Analysis of Long-Term Changes in Extreme Waves in the Northwest Pacific Over the Past 60 Years

Abstract. This study analyses wave height trends in the Northwest Pacific over the past 60 years and estimates design wave heights across various return periods to assess the resilience of marine and coastal structures to extreme wave events. Design wave height is a critical parameter for evaluating structural stability and safety, especially during typhoon season (May to October), when strong winds and rapid movements often trigger extreme waves, significantly impacting offshore structures, coastlines, and ports. To avoid underestimating risks during typhoon season, this study simulated wave heights from 1961 to 2020 using historical wind field data from the EC-Earth3 climate model and the WAVEWATCH III wave model. The 95th percentile was chosen as the threshold for extreme wave events, and the Generalized Pareto Distribution (GPD) model was applied for fitting. Finally, the bootstrap resampling method was used to quantify uncertainties in return periods to ensure reliable assessments of design wave heights. The analysis shows a slight increase in design wave heights with longer return periods (10 to 200 years) near Taiwan, with significantly higher wave heights observed in the southern and eastern regions, indicating a need to enhance disaster resilience in marine infrastructure designs for these areas.