the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 May 2026
The applications of UFS-Coastal v1.0.0b01: wave-current coupling of SCHISM and WAVEWATCH III
Abstract. Accurate prediction of coastal flooding and nearshore processes requires a coupled modeling framework that resolves interactions among ocean circulation, surface waves, ice, and atmospheric forcing across complex coastal geometries. To address this need, we present Unified Forecast System Coastal model (UFS-Coastal), a coupled coastal modeling framework extending the Unified Forecast System Weather Model (UFS-WM). The UFS-Coastal was developed to address this need by disentangle extending the prior infrastructure (called CoastalApp), and combining CaostalApp and UFS-WM, and byintegrating four different coastal hydrodynamic models: SCHISM, ADCIRC, FVCOM, and ROMS, along with the spectral wave model WAVEWATCH III (WW3) and CICE within a unified coupled framework. Here we introduce UFS-Coastal to the community, and focus on one particular aspect, the wave-current coupling between SCHISM and WW3 with two methods: the Longuet-Higgins radiation stress formulation and a three-dimensional (3D) vortex approach. We provide a comprehensive description of UFS-Coastal’s infrastructure, coupling methodologies, and its automated regression testing framework. The system’s performance is demonstrated through experiments in the Duck, North Carolina (NC) region against Field Research Facility observations. Both wave-current coupling schemes between the SCHISM and WW3 could successfully reproduce observed coastal hydrodynamics and wave conditions; notably, the 3D vortex coupling improved simulations of wave-induced mixing in shallow and stratified environments. Overall, UFS-Coastal offers a robust framework for accurate prediction of coastal flooding, storm surge events, and wave-current interactions, supporting both research and operational forecasting applications.
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Status: open (until 22 Jul 2026)
- RC1: 'Comment on egusphere-2026-1941', Anonymous Referee #1, 23 Jun 2026 reply
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More model setup description: Could the authors provide a more detailed description of the model setup? Specifically, are open boundary conditions applied to the lateral boundaries (the north and south boundaries) as well?
Justification on model domain: The authors utilize a relatively small model domain that extends only about 10–20 km offshore. This implies that the model results, particularly the nearshore dynamics, will be heavily influenced by the open boundary conditions. Consequently, the simulated storm surge could be driven purely by the open boundary setup. The authors need to justify the choice of this domain size and discuss its potential artifacts.
Wave simulation results (Fig. 4): Regarding the wave simulation results in Figure 4, the model appears to notably underestimate the wave height at the 6m and 8m stations, yet it surprisingly performs very well at the 2m station. At the 2m station, the wave height exhibits a clear semi-diurnal signal; is this due to tidal influence? Additional elaboration and explanation of these model results should be provided. Currently, the manuscript dedicates 12 pages to introductory material and only 1 page to the results.
3D Vortex Scheme and Cross-Shore Velocity: The most interesting finding from this study is that the 3D vortex scheme yields a fundamentally different cross-shore velocity field. The authors claim that "3D vortex simulations aligned closely with real observations, capturing the vertical gradients and mixing patterns missing in the Longuet-Higgins approach."However, how is it determined that the 3D vortex simulations are closer to reality? Is there observational data available to support this claim? Furthermore, the simulated cross-shore velocity is extremely large, exceeding 0.5 m/s. Is this physically realistic? What is the maximum cross-shore velocity simulated by the model? In most coastal environments, cross-shore velocity is expected to be much weaker than alongshore velocity.
Minor comments:
Fig 6: please indicate what is the direction for positive and negative velocity in both alongshore and cross-shore velocities. Also add x and y labels.