Global extreme significant wave height within the dominant directional sector

Abstract

The assessment of global directional extreme significant wave height (SWH) is crucial for the ocean infrastructure, which requires the dominant directional sector to be identified. In this study, 40-year (1979–2018) global SWHs and wave directions obtained from ERA5 are employed as the initial database. To study the extreme wave, storms over the initial threshold are extracted, which show that the non-tropical cyclonic storm is stable with the direction and most directions are within the dominant directional sector. Thus, the directional extrapolation is performed based on the independent non-tropical cyclone sample. To identify the dominant directional sector, an automated method is proposed based on the circular mean sample. Benefiting from this method, global patterns of sector width and representative direction of dominant directional sector can be obtained and classified. To make sufficient use of extreme samples for reasonable extrapolation, the peak over threshold method with the generalized Pareto distribution model is employed to evaluate the global directional extreme SWHs. The spatially comparable patterns accord with the distribution of wind zones and reveal the effect of swells in low latitudes, which can be used to realize design optimization and key protection of ocean infrastructures, especially for infrastructures that are not symmetrical.