Impacts of Wave-Current Interaction in Coupled Storm Surge-Wave Model

The existing two-dimensional Advanced Circulation (ADCIRC) storm surge model solves for the depth integrated Eulerian currents and sea surface elevation. In the ADCIRC-wave coupled model, the impact of the surface waves on the storm surge is represented by radiation stress gradient forcing. However, recent studies suggest that the effects of waves on ocean currents and water elevation cannot be completely captured by radiation stress alone. In this study, we rewrite the ADCIRC continuity and momentum equations in terms of the vertically integrated Lagrangian currents (Eulerian currents plus the Stokes drift), to fully account for wave-current interactions. This modification introduces a new wave-induced forcing term (P) in the momentum equations, which depends on both waves and currents. We incorporated the P forcing term into the ADCIRC-Wavewatch III (WW3) coupled model and conducted simulations of Hurricanes Michael (2018) and Ian (2022). The results indicate that the radiation stress forcing leads to a significant water level increase (by 0.4 m or more) over a large area to the right of the storm track. In contrast, the P forcing causes a notable water level reduction (up to 0.3 m) near the storm track, shortly before the storm makes landfall. This reduction is attributed to the alignment of storm-induced currents and waves in the alongshore direction.