Long-Term Extreme Wave Characteristics in the Water Adjacent to China Based on ERA5 Reanalysis Data

Extreme waves have a profound impact on coastal infrastructure; thus, understanding the variation law of risky analysis and disaster prevention in coastal zones is necessary. This paper analyzed the spatiotemporal characteristics of extreme wave heights adjacent to China from 1979 to 2018 based on the ERA5 datasets. Nonstationary extreme value analysis is undertaken in eight representative points to investigate the trends in the values of 50- and 100-year wave heights. Results show that the mean value of extreme waves is the largest in the eastern part of Taiwan Island and the smallest in the Bohai Sea from 1979 to 2018. Only the extreme wave height in the northeastern part of Taiwan Island shows a significant increase trend in the study area. Nonstationary analysis shows remarkable variations in the values of 50- and 100-year significant wave heights in eight points. Considering the annual mean change, E1, E2, S1, and S2 present an increasing trend, while S3 shows a decreasing trend. Most points for the seasonal mean change demonstrate an increasing trend in spring and winter, while other points show a decreasing trend in summer and autumn. Notably, the E1 point growth rate is large in autumn, which is related to the change in typhoon intensity and the northward movement of the typhoon path.