A global wave parameter database for geophysical applications. Part 1: Wave-current–turbulence interaction parameters for the open ocean based on traditional parameterizations (original) (raw)
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WIND WAVES IN THE GLOBAL OCEAN OBSERVING SYSTEM
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The Wave-Driven Ocean Circulation
Oceanic surface gravity waves have a mean Lagrangian motion, the Stokes drift. The dynamics of winddriven, basin-scale oceanic currents in the presence of Stokes drift are modified by the addition of so-called vortex forces and wave-induced material advection, as well by wave-averaged effects in the surface boundary conditions for the dynamic pressure, sea level, and vertical velocity. Some theoretical analyses previously have been made for the gravity wave influences on boundary-layer motions, including the Ekman currents. The present paper extends this theory to the basin-scale, depth-integrated circulation in a bounded domain. It is shown that the Sverdrup circulation relation, with the meridional transport proportional to the curl of the surface wind stress, applies to Lagrangian transport, while the associated Eulerian transport is shown to have a component opposite to the Stokes-drift transport. A wave-induced correction to the relation between sea level and surface dynamic pressure is also derived. Preliminary assessments are made of the relative importance of these influences using a global wind climatology and an empirical relationship between the wind and wave fields. Recommendations are made for further development and testing of this theory and for its inclusion in general circulation models.
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2002
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A preliminary estimate of the Stokes dissipation of wave energy in the global ocean
Geophysical Research Letters, 2009
1] The turbulent Reynolds stresses in the upper layers of the ocean interact with the vertical shear of the Stokes drift velocity of the wave field to extract energy from the surface waves. The resulting rate of dissipation of wind waves in the global ocean is about 2.5 TW on the average but can reach values as high as 3.7 TW, making it as important as the dissipation of wave energy in the surf zones around the ocean margins. More importantly, the effect of Stokes dissipation is felt throughout the mixed layer. It also contributes to Langmuir circulations. Unfortunately, this wave dissipation mechanism has hitherto been largely ignored. In this note, we present a preliminary estimate of the Stokes dissipation rate in the global oceans based on the results of the WAVEWATCH III model for the year 2007 to point out its potential importance. Seasonal and regional variations are also described. Citation: Kantha, L., P. Wittmann, M. Sclavo, and S. Carniel (2009), A preliminary estimate of the Stokes dissipation of wave energy in the global ocean, Geophys.
J. Phys. Oceanogr …, 2011
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.
A three-dimensional surface wave–ocean circulation coupled model and its initial testing
Ocean Dynamics, 2010
A theoretical framework to include the influences of nonbreaking surface waves in ocean general circulation models is established based on Reynolds stresses and fluxes terms derived from surface wave-induced fluctuation. An expression for the wave-induced viscosity and diffusivity as a function of the wave number spectrum is derived for infinite and finite water depths; this derivation allows the coupling of ocean circulation models with a wave number spectrum numerical model. In the case of monochromatic surface wave, the wave-induced viscosity and diffusivity are functions of the Stokes drift. The influence of the wave-induced mixing scheme on global ocean circulation models was tested with the Princeton Ocean Model, indicating significant improvement in upper ocean thermal structure and mixed layer depth compared with mixing obtained by the Mellor–Yamada scheme without the wave influence. For example, the model–observation correlation coefficient of the upper 100-m temperature along 35° N increases from 0.68 without wave influence to 0.93 with wave influence. The wave-induced Reynolds stress can reach up to about 5% of the wind stress in high latitudes, and drive 2–3 Sv transport in the global ocean in the form of mesoscale eddies with diameter of 500–1,000 km. The surface wave-induced mixing is more pronounced in middle and high latitudes during the summer in the Northern Hemisphere and in middle latitudes in the Southern Hemisphere.
Geoscientific Model Development Discussions
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Geophysical Research Letters, 2004
1] From the Reynolds stress expression, the waveinduced vertical viscosity (or diffusivity) Bv is defined, which can be used as a parameter to estimate the strength of wave-induced mixing. In addition, a parameter D 5 is introduced to represent a wave-induced mixing penetration depth. The global distribution of Bv averaged over the upper 20 m is calculated and its latitudinal transects in boreal summer and winter is discussed. The results show that in summer the wave-induced mixing is strong in the southern oceans south of 30°S, and in winter it is strong in the north Pacific and the north Atlantic north of 30°N, as well as in the southern oceans south of 40°S. Adding Bv to the vertical diffusivity in a global ocean circulation model yields a temperature structure in the upper 100 m that is closer to the observed climatology than a model without the waveinduced mixing. (2004), Waveinduced mixing in the upper ocean: Distribution and application to a global ocean circulation model, Geophys.
Modelling the Effect of Ocean Waves on the Atmospheric and Ocean Boundary Layers
Energy Procedia, 2012
Ocean waves, in addition to generating direct forces on fixed and floating offshore wind generator structures, also have significant indirect effects via their influence on the atmospheric and oceanic boundary layers above and below the water surface. In the atmospheric boundary layer the waves act as roughness elements, influencing the turbulent flow and the vertical wind speed profile, and induce oscillatory motions in the airflow. Spray droplets from breaking wave crests enhance structure corrosion, and may lead to icing under low-temperature conditions. Below the water surface, the air-sea momentum flux and mechanical energy flux, mediated by the waves and wave-generated turbulence, affect the vertical profiles of ocean current, temperature, and salinity. Effects include modifying the structural forces and dynamics, and the movement and dispersion of marine organisms, pollutants, and air bubbles generated by breaking waves, with consequences for fouling, corrosion, and environmental impact. Measurement of relevant airflow and ocean dynamical variables is also challenging, as near the water surface it is often necessary to use instruments mounted on moving measurement platforms.