Parameterizing the Effects of Finite Crested Wave Breaking in Wave-Averaged Models
Nirnimesh Kumar, Scripps Institution of Oceanography, Integrative Oceanography Division, La Jolla, CA, United States, Sutara H Suanda, Scripps Institution of Oceanography, La Jolla, CA, United States and Falk Feddersen, University of California San Diego, La Jolla, CA, United States
Abstract:
Finite crested breaking waves generate a rotational body force that creates two-dimensional turbulent eddies with strong rotational velocities, capable of tracer exchange (sediment, pathogens, contaminants) between the surfzone and the inner shelf. This eddy generation mechanism is strongly tied to the wave directional spread. Wave-resolving Boussinesq models like
funwaveC include finite crest length breaking and accurately simulate surfzone eddy generation. However, this surfzone eddy generation mechanism is not included in existing wave-averaged models (e.g.,
Coupled Ocean Atmosphere Wave Sediment Transport Modeling System, COAWST), leading to an incomplete representation of exchange between the surf zone and the inner shelf.
In this study ~250 funwaveC simulations with random, directionally spread waves spanning a range of beach slopes and wave conditions are used to simulate surfzone eddies. With these simulations, the stream function associated with breaking wave eddy forcing is isolated and quantified in the form of intensity, cross- and alongshore widths and propagation rates, followed by parameterization as a function of wave parameters and the beach slope. Parameterized stream function is implemented into COAWST as a stochastic surf zone eddy module which is used to study vorticity evolution from the surfzone to the inner-shelf, interaction between stratified water column and surfzone eddies, and overall provides a more complete representation of surfzone eddy induced cross-shore exchange. Funded by the Office of Naval Research.
