Abstract
Ocean waves represent a large amount of clean renewable energy that could be harvested to power systems from a commercial grid scale to small stand-alone applications. Renewable wave energy development can improve energy security and enhance community resilience for American Samoa. This study presents a model and satellite-based analysis of the wave climate around American Samoa. The wave resources are analyzed based on a 42-year hindcast from 1979 to 2020. The hindcast was generated using the unstructured version of SWAN for the exclusive economic zone (EEZ) with wind forcing obtained from NOAA’s CFSR and CFSv2 hindcasts. The SWAN model is nested in a multi-resolution Wavewatch III (WW3) v5.16 model, which comprises two regional structured grids around the Central Pacific Islands with boundary conditions from the global version of NOAA’s WW3. The unstructured SWAN mesh has a spatial resolution of ~100 m at the coastline and is relaxed to 5 km in deep water. Measurements from PACIOOS buoy 189 off the east coast of Tutuila were used for validation. Significant wave height derived from satellite-based altimeters were used to complement the buoy measurements in understanding the spatial variability of the model errors. Typical linear correlation coefficients for significant wave height exceed 0.9 and RMSEs are within 30 cm. Sensitivity analyses were conducted during model setup to evaluate the tradeoff between model iterations and time step, along with their implications on wave propagation speed and numerical errors. Detailed wave energy assessment is performed for the nearshore regions and sites of interest, closely following the IEC standards. Finally, inter-annual and seasonal variations of the wave characteristics are presented with a focus on the multi-modal sea states.