23COASTAL High-Resolution Wave Forecasting System Incorporating Wave-Current Interactions at the Columbia River

Estuarine hydrodynamics are inherently complex due to the combined effects of tides, waves, and river discharges. The interaction between currents and waves is particularly critical and must be carefully considered when analyzing estuarine dynamics. In recent decades, there has been a growing interest in wave-current interactions. Extensive research has demonstrated that tidal flows significantly impact wave propagation in shallow waters, with tidal variations causing changes in wave height. Opposing tides tend to increase wave height, while following tides reduce it. Additionally, the direction of wave and current propagation plays a crucial role in how waves affect currents.

Our primary focus is the mouth of the Columbia River (MCR), with future expansions to include estuaries such as Yaquina Bay, Oregon. The Columbia River, the second-largest river in the United States, serves as a critical gateway to several commercial ports, accommodating over 12,000 commercial vessels and 100,000 recreational and charter vessels annually. The MCR is particularly known for its challenging wave conditions and navigation hazards. The MCR experiences strong tidal currents due to the constriction of tidal flows through its narrow entrance. Studies have shown that these currents can dramatically influence local wave heights. Therefore, we aim to integrate wave-current interactions into the spectral wave model (WAVEWATCH III), using unstructured grids to capture the spatial variability at these dynamic estuary mouths, especially in the Pacific Northwest where significant tidal ranges and freshwater discharges occur.

Global ocean modeling has typically focused on large-scale processes, but there is increasing interest in understanding smaller-scale phenomena. Emerging models now offer high resolution, fully resolving eddies, and more frequently incorporate barotropic and baroclinic tides, which are crucial for ocean mixing and the global energy budget. Improving nearshore tide models can enhance the accuracy of open-ocean tides, especially in energetic regions like the North Atlantic. However, representing the complex geometry and bathymetry of coastal areas requires high-resolution data, posing significant computational challenges. Unstructured-grid models can help mitigate these costs. Despite advancements, many global models still cannot simultaneously include estuaries and rivers without grid nesting due to the differing spatial scales and force balances between global and coastal systems. Some global models are now developing coastal components to better integrate these systems.

Our research focuses on developing, testing, and validating a high-resolution wave forecasting system that incorporates wave-current interactions through one way coupling with existing estuarine circulation models. We acknowledge the ongoing parallel efforts to build circulation forecasting models for estuaries in the Pacific Northwest. For example, the "Virtual Columbia River" model, originally developed at the Center for Coastal Margin Observations and Prediction (CMOP) and now managed by the Columbia River Inter-Tribal Fish Commission (CRITFC), is an operational circulation model transitioning to a SCHISM-based engine for integration into NOAA's Surge and Tide Operational Forecast System (STOFS). Recent efforts have developed a larger domain SCHISM-based model of the Pacific basin, incorporating tidal, atmospheric, and 3D baroclinic ocean forcings, currently being transferred to NOAA’s Office of Coast Survey (OCS) for pre-operational testing.

Additionally, the Salish Sea and Columbia River Operational Forecast System (SSCOFS) is a developmental circulation forecasting system focusing on the Columbia River and extending to Yaquina Bay, OR. This system was developed through a joint project involving NOAA's Center for Operational Oceanographic Products and Services (CO-OPS), Office of Coast Survey, National Weather Service's (NWS) National Centers for Environmental Prediction Central Operations, Battelle - Pacific Northwest National Laboratory, and the University of Massachusetts-Dartmouth. SSCOFS provides the maritime community with nowcast and forecast guidance of water levels, currents, water temperature, and salinity.

Given these extensive efforts, it is an opportune time to validate a high-resolution wave forecasting system that integrates wave-current interactions at key estuaries in the Pacific Northwest. Our objective is to assess the accuracy of WAVEWATCH III's wave predictions using different circulation models to identify the required spatial resolution and the effectiveness of model coupling. This initiative will involve detailed analyses of remote sensing data and in situ wave measurements for validation.