Semiempirical Dissipation Source Functions for Ocean Waves. Part I: Definition, Calibration, and Validation

Abstract

New parameterizations for the spectral dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum, in a way consistent with observation of wave breaking and swell dissipation properties. Namely, swell dissipation is nonlinear and proportional to the swell steepness, and wave breaking only affects spectral components such that the non-dimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short wave dissipation due to long wave breaking is introduced, together with a reduction of wind-wave generation term for short waves, otherwise taken from Janssen (J. Phys. Oceanogr. 1991). These parameterizations are combined and calibrated with the Discrete Interaction Approximation of Hasselmann et al. (J. Phys. Oceangr. 1985) for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but the parameterizations probably yield the most accurate overall estimate of wave parameters to date. Perspectives for further improvement are also given.

Effects of waves on coastal water dispersion in a small estuarine bay

“…WWIII has been widely validated at global and regional scales [e.g., Tolman, 2002;Ardhuin et al, 2008aArdhuin et al, , 2010, and more recently in nearshore areas [e.g., Filipot and Michaud et al, 2012;Ardhuin et al, 2012]. The model solves the spectral balance equation for the wave action density N, with source terms S in , S nl , S oc , and S bot for wind input, nonlinear four-waves interactions, wave breaking dissipation and bottom friction dissipation, respectively.…”

“…s aw and s wo are computed from spectral wave energy source terms S in and S oc , respectively (introduced in paragraph 3.2. ), according to Ardhuin et al [2009Ardhuin et al [ , 2010.…”

Atmospheric storm surge modeling methodology along the French (Atlantic and English Channel) coast

“…The drag coefficient is wind-and wave-dependent; it is computed from the Charnock formulation. Charnock coefficients come from global WAVEWATCH III® model of IOWAGA project (Ardhuin et al 2010) as described in Sect. 3.2.…”

“…(3). In the present study, α c is constant or variable (α cvar ) and, in this case, issued from the IOWAGA modeling system (Rascle and Ardhuin 2013) which is based on the wave model WAVEWATCH III® (Tolman 2008;Ardhuin et al 2010;Tolman et al 2013). Within the wave model, α c comes from Eq.…”

“…(6), thanks to the iterative computation of the friction velocity using the wave growth rate following the parameterization of Janssen et al (1994) as used at European Centre for Medium-Range Weather Forecasts (ECMWF). An important difference, though, is that the parameterization for the wave breaking and generation terms are different from those of ECMWF (Bidlot 2012), in particular because Ardhuin et al (2010) include a reduction of the wavesupported stress in the high frequencies to represent a sheltering of short waves by longer waves. Although this parameterization leads to better short wave properties, it removes most of the wave-induced variability in the Charnock coefficient (Rascle and Ardhuin 2013).…”