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Regional wave data were obtained by downscaling the 7-years hindcast of the  Centre for Australian Weather and Climate Research (CAWCR) using the unstructured version of SWAN (Simulating WAves Nearshore; Booij et al., 1999). 

In a complex environment such as the Republic of Marshal Islands (RMI archipelago), filled with numerous scattered islands and seamounts, fine resolution model is required where sudden changes in the wave fields are expected. Global wave hindcasts in RMI do not resolve wave shadowing and blocking and wind wave growth to the leeward side of the islands. For this wave hindcast, the OceanMesh2D software (Roberts & Pringle, 2019) has been used to generate a high-resolution flexible mesh, resolving the 28 islands contained in the numerical domain.

To avoid numerical instabilities due to a misrepresentation of the local bathymetry over the islands, atoll lagoons have been removed from the numerical domain. The peculiar shape of the outer boundary was a compromise between the availability of stored 2D spectra in the CAWCR hindcast (total of 55 points) and the minimum area required to compensate the deficiencies of the global wave model. The resulting mesh covered 728.790 km2 with 32185 triangles of varying size formed by 62234 vertices. Resolution ranged from 1 km around the islands to 10 km in the open ocean. The bathymetry for this large-scale model was obtained from SRTM15+ only.

The SWAN model used as many default parameters as possible: wind input of Komen et al. (1984) based on Snyder et al. (1981) and whitecapping and quadruplets based on Hasselmann (1974). The model used a spectral resolution of 36 directions and 32 frequency intervals from 1 to 30 s.