Including Wave Rollers in a Regional Scale Coupled Modeling System for Nearshore Applications

In support of utilizing the Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS) at surf zone resolving horizontal resolutions, we employ an empirical approximation of the wave roller energy. The wave roller is the turbulent area on the face of a breaking wave that travels with the wave and distributes the decay in wave energy to turbulence over a transition zone. It is included in the calculation of radiation stress, the gradients of which drive the flow through the momenum balance. It has been reported that inclusion of the wave roller shifts the maximum in velocity shoreward, alleviates models' tendencies to predict zero velocity when waves reform in a bar trough, and improves model-data comparisons for laboratory and field experiments. We evalutate our implementation of a wave roller approximation in COAMPS over three idealized bathymetric profiles, a plane beach, a shallow-barred beach and a deep-barred beach. In all three cases, the roller approximation shifts the maximum velocity shoreward. We investigate unexpected velocity reversals, explain the cause of the reversals, and suggest methods to alleviate the reversals.