Wave‐turbulence interaction and its induced mixing in the upper ocean

Abstract

[1] In the ocean, interaction among the mean current, the surface waves, and turbulence is a major mechanism for energy transfer from surface waves to the turbulence field. This process is associated with attenuation of surface waves. This paper deals with waveturbulence interaction and its induced mixing using field observations and a onedimensional, level 2.5 turbulence closure model. The results show that both the turbulence kinetic energy dissipation rate and the vertical mixing induced by wave-turbulence interaction are a function of u s0 u * 2 and wave parameters, where u s0 is the Stokes drift at the sea surface and u * is the friction velocity in water. The former decays with the depth away from the surface in the form of e 2kz , while the latter decays as e 3kz (k is the wave number). We also analyze the wave decay induced by wave-turbulence interaction. The decay time scale is in proportion to cL/u * 2 , while in inverse proportion to ffiffi ffi p , where c is a phase speed, L is a wavelength, and d is a wave steepness. A series of numerical experiments are performed to evaluate the effects of wave-turbulence interaction. The results from the cases with effects of wave-turbulence interaction show significant improvement in simulation of turbulence characteristics compared to the cases in the absence of surface waves. This implies that wave-turbulence interaction is a significant mechanism for generation of turbulence kinetic energy in the upper ocean and plays an important role in regulating vertical mixing and surface wave decay.

Modeling the Effect of Waves on the Diurnal Temperature Stratification of a Shallow Lake

“…If the wave spectrum is narrow enough bulk parameters can indeed characterize the effect of the irregular wave motion with sufficient accuracy, as opposed to deriving turbulent mixing and shear production from the spectrum [19]. In the absence of a wave spectrum (modeled or measured), many researchers successfully applied mixing parametrizations based on bulk characteristic [14,23] but it has to be underlined that several studies reported that model results improve significantly by using a 2D spectral wave model since wave mixing can be overestimated by bulk parametrizations [25,26].…”

“…(8) to observations [26]. Huang and Qiao [23] determined its value as 1 for a medium-size lake which is featured by wave motion similar to that of Lake Balaton. The observed wave height and period were 0.25 m and 4 s [27].…”

“…However, in Lake Balaton, long fetches may develop, extending the studied length scales upwards. The another way to account for mixing by non-breaking waves is to introduce into the TKE equation the production by waves (P wave ) in addition to the production by the mean shear [21,23]:…”

“…where u * is the water-side friction velocity, δ = H s ⁄ L is the wave steepness, β is an empirical parameter, which can be calibrated from observations and which does not exceed 1 according to [23].…”

Wave‐induced transport and vertical mixing of pelagic eggs and larvae

“…These types of models typically predict low levels of mixing near the surface due to the assumption of wall-type flow near the surface, which is inconsistent with the observation that particles are efficiently mixed downward during storms (e.g., oil droplets and pelagic eggs). Also, observations of turbulent dissipation in the upper ocean show deviations from law-of-the-wall behavior near the surface (Huang and Qiao 2010;Sutherland et al 2013). Consequently, diffusivity profiles from second-order closures often yield unrealistic results for plankton diffusion (Curtis et al 2007).…”