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Noyes et al. 2005
Noyes, T.J., Guza, R.T., Feddersen, F., Elgar, S. and Herbers, T.H.C. (2005). Model-data comparisons of shear waves in the nearshore. Journal of Geophysical Research 110: doi: 10.1029/2004JC002541. issn: 0148-0227.

Observations of shear waves, alongshore propagating meanders of the mean alongshore current with periods of a few minutes and alongshore wavelengths of a few hundred meters, are compared with model predictions based on numerical solutions of the nonlinear shallow water equations. The model (after ¿zkan-Haller and Kirby (1999)) assumes alongshore homogeneity and temporally steady wave forcing and neglects wave-current interactions, eddy mixing, and spatial variation of the (nonlinear) bottom drag coefficient. Although the shapes of observed and modeled shear wave velocity spectra differ, and root-mean-square velocity fluctuations agree only to within a factor of about 3, aspects of the cross-shore structure of the observed (~0.5--1.0 m above the seafloor) and modeled (vertically integrated) shear waves are qualitatively similar. Within the surf zone, where the mean alongshore current (V) is strong and shear waves are energetic, observed and modeled shear wave alongshore phase speeds agree and are close to both V and Clin (the phase speed of linearly unstable modes) consistent with previous results. Farther offshore, where V is weak and observed and modeled shear wave energy levels decay rapidly, modeled and observed C diverge from Clin and are close to the weak alongshore current V. The simulations suggest that the alongshore advection of eddies shed from the strong, sheared flow closer to shore may contribute to the offshore decrease in shear wave phase speeds. Similar to the observations, the modeled cross- and alongshore shear wave velocity fluctuations have approximately equal magnitude, and the modeled vorticity changes sign across the surf zone.

BACKGROUND DATA FILES

Abstract

Keywords
Oceanography, Physical, Nearshore processes, Oceanography, Physical, Surface waves and tides, Oceanography, Physical, Turbulence, diffusion, and mixing processes, shear waves, longshore currents, surf zone
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
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