Investigating the uncertainty of coupled ocean-wave-atmosphere mesoscale model in simulating significant wave height along the California Coast

With the objective of establishing 30 gigawatts of offshore wind capacity by 2030 (U.S. DOE), the wind energy lease sales were held for the first time along the U.S. West Coast in 2022. However, the impact of atmospheric and oceanographic conditions on offshore wind plants is largely unknown. Furthermore, the accuracy of existing high-resolution coupled ocean-atmosphere models in estimating air-sea interaction is questionable because of the complex wind-wave-terrain interactions observed in this region.

In this study, we investigate the uncertainty of the coupled ocean-wave-atmosphere mesoscale model in simulating significant wave height along the California coast by conducting mesoscale simulations using the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling system. In particular, model configuration is made use of atmospheric (WRF), wave (WAVEWATCH III) and oceanic (ROMS) model at kilometer-scale grid spacing, all of which mutually interact with each other. Two significant wave height periods (3 ~ 4 days) have been identified from the National Data Buoy Center (NDBC) stations. Interestingly, the model prediction of significant wave height is significantly better in one event than the other (See attached figure). The ability of coupled mesoscale models to accurately capture such significant wave event is currently not well known but vastly important for site-selection and construction for the offshore wind plant. Therefore, the associated modeling uncertainties need to be addressed. This evaluation will help quantify model errors, identify conditions for which model physics works and conditions for which it may need improvement, and determine the impact of the coupling modes on simulating the significant wave fields.