Surf zone currents over irregular bathymetry: Drifter observations and numerical simulations

摘要: [1] Surf zone currents over irregular bathymetry were observed with GPS-tracked drifters and modeled the depth-integrated nonlinear shallow water equations. Trajectories of released in 1–2 m depth sometimes defined rip surf eddies, features that have been difficult to resolve fixed instruments. The drifter-delineated circulation evolved as tidal level changed during each 4–6 hour deployment. In one case, tide dropped, a shore normal current present for first 2 hours more parallel flow. second on rising well-developed bifurcated was replaced by weak, amorphous circulation. Rip velocities strongest near edge decayed an order magnitude within widths from shoreline. An eddy persist bathymetric depression at least 1 hour. Observed numerically simulated drifter trajectories define similar flow features, but differed roughly factor 2, evolution 0.5 changes reproduced only if levels varied about m. alongshore momentum balance spatially variable, wave forcing balanced pressure gradient, friction, advective terms. cross-shore everywhere dominated gradient terms equal magnitude. vicinity residual increased advection