scholarly journals Turbulence Scaling Comparisons in the Ocean Surface Boundary Layer

2018 ◽  
Vol 123 (3) ◽  
pp. 2172-2191 ◽  
Author(s):  
L. Esters ◽  
Ø. Breivik ◽  
S. Landwehr ◽  
A. ten Doeschate ◽  
G. Sutherland ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ocean Surface ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Turbulence Scaling

scholarly journals A global perspective on Langmuir turbulence in the ocean surface boundary layer

2012 ◽  
Vol 39 (18) ◽  
Author(s):  
Stephen E. Belcher ◽  
Alan L. M. Grant ◽  
Kirsty E. Hanley ◽  
Baylor Fox-Kemper ◽  
Luke Van Roekel ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ocean Surface ◽  
Global Perspective ◽  
Surface Boundary ◽  
Langmuir Turbulence ◽  
Surface Boundary Layer

LESbrary: A library of large eddy simulation data for the calibration and uncertainty quantification of ocean surface boundary layer turbulence parameterizations

2021 ◽  
Author(s):  
Gregory Wagner ◽  
Andre Souza ◽  
Adeline Hillier ◽  
Ali Ramadhan ◽  
Raffaele Ferrari
Keyword(s):  
Boundary Layer ◽  
Turbulent Mixing ◽  
Large Scale ◽  
Ocean Surface ◽  
Limited Area ◽  
Surface Boundary ◽  
Model Errors ◽  
Surface Boundary Layer ◽  
Large Eddy ◽  
Free Parameters

<p>Parameterizations of turbulent mixing in the ocean surface boundary layer (OSBL) are key Earth System Model (ESM) components that modulate the communication of heat and carbon between the atmosphere and ocean interior. OSBL turbulence parameterizations are formulated in terms of unknown free parameters estimated from observational or synthetic data. In this work we describe the development and use of a synthetic dataset called the “LESbrary” generated by a large number of idealized, high-fidelity, limited-area large eddy simulations (LES) of OSBL turbulent mixing. We describe how the LESbrary design leverages a detailed understanding of OSBL conditions derived from observations and large scale models to span the range of realistically diverse physical scenarios. The result is a diverse library of well-characterized “synthetic observations” that can be readily assimilated for the calibration of realistic OSBL parameterizations in isolation from other ESM model components. We apply LESbrary data to calibrate free parameters, develop prior estimates of parameter uncertainty, and evaluate model errors in two OSBL parameterizations for use in predictive ESMs.</p>

scholarly journals Horizontal Dispersion of Buoyant Materials in the Ocean Surface Boundary Layer

2018 ◽  
Vol 48 (9) ◽  
pp. 2103-2125 ◽  
Author(s):  
Jun-Hong Liang ◽  
Xiaoliang Wan ◽  
Kenneth A. Rose ◽  
Peter P. Sullivan ◽  
James C. McWilliams
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Ocean Surface ◽  
Turbulent Dispersion ◽  
Surface Boundary ◽  
Particle Trajectories ◽  
Stokes Flows ◽  
Surface Boundary Layer ◽  
Horizontal Dispersion ◽  
Shear Dispersion

ABSTRACTThe horizontal dispersion of materials with a constant rising speed under the exclusive influence of ocean surface boundary layer (OSBL) flows is investigated using both three-dimensional turbulence-resolving Lagrangian particle trajectories and the classical theory of dispersion in bounded shear currents generalized for buoyant materials. Dispersion in the OSBL is caused by the vertical shear of mean horizontal currents and by the turbulent velocity fluctuations. It reaches a diffusive regime when the equilibrium vertical material distribution is established. Diffusivity from the classical shear dispersion theory agrees reasonably well with that diagnosed using three-dimensional particle trajectories. For weakly buoyant materials that can be mixed into the boundary layer, shear dispersion dominates turbulent dispersion. For strongly buoyant materials that stay at the ocean surface, shear dispersion is negligible compared to turbulent dispersion. The effective horizontal diffusivity due to shear dispersion is controlled by multiple factors, including wind speed, wave conditions, vertical diffusivity, mixed layer depth, latitude, and buoyant rising speed. With all other meteorological and hydrographic conditions being equal, the effective horizontal diffusivity is larger in wind-driven Ekman flows than in wave-driven Ekman–Stokes flows for weakly buoyant materials and is smaller in Ekman flows than in Ekman–Stokes flows for strongly buoyant materials. The effective horizontal diffusivity is further reduced when enhanced mixing by breaking waves is included. Dispersion by OSBL flows is weaker than that by submesoscale currents at a scale larger than 100 m. The analytic framework will improve subgrid-scale modeling in realistic particle trajectory models using currents from operational ocean models.

scholarly journals Assessing the Effects of Langmuir Turbulence on the Entrainment Buoyancy Flux in the Ocean Surface Boundary Layer

2017 ◽  
Vol 47 (12) ◽  
pp. 2863-2886 ◽  
Author(s):  
Qing Li ◽  
Baylor Fox-Kemper
Keyword(s):  
Boundary Layer ◽  
Climate Model ◽  
Ocean Surface ◽  
Buoyancy Flux ◽  
Entrainment Rate ◽  
Surface Boundary ◽  
Langmuir Turbulence ◽  
Convective Turbulence ◽  
Surface Boundary Layer ◽  
The Impact

AbstractLarge-eddy simulations (LESs) with various constant wind, wave, and surface destabilizing surface buoyancy flux forcing are conducted, with a focus on assessing the impact of Langmuir turbulence on the entrainment buoyancy flux at the base of the ocean surface boundary layer. An estimate of the entrainment buoyancy flux scaling is made to best fit the LES results. The presence of Stokes drift forcing and the resulting Langmuir turbulence enhances the entrainment rate significantly under weak surface destabilizing buoyancy flux conditions, that is, weakly convective turbulence. In contrast, Langmuir turbulence effects are moderate when convective turbulence is dominant and appear to be additive rather than multiplicative to the convection-induced mixing. The parameterized unresolved velocity scale in the K-profile parameterization (KPP) is modified to adhere to the new scaling law of the entrainment buoyancy flux and account for the effects of Langmuir turbulence. This modification is targeted on common situations in a climate model where either Langmuir turbulence or convection is important and may overestimate the entrainment when both are weak. Nevertheless, the modified KPP is tested in a global climate model and generally outperforms those tested in previous studies. Improvements in the simulated mixed layer depth are found, especially in the Southern Ocean in austral summer.

Wind- and Wave-driven Ocean Surface Boundary Layer in a Frontal Zone: Roles of Submesoscale Eddies and Ekman-Stokes Transport

2021 ◽  
Author(s):  
Jianguo Yuan ◽  
Jun-Hong Liang
Keyword(s):  
Boundary Layer ◽  
Frontal Zone ◽  
Surface Current ◽  
Ocean Surface ◽  
Buoyancy Flux ◽  
Temperature Structure ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Horizontal Mixing ◽  
The Right

AbstractLarge-eddy simulations are used to investigate the influence of a horizontal frontal zone, represented by a stationary uniform background horizontal temperature gradient, on the wind- and wave-driven ocean surface boundary layers. In a frontal zone, the temperature structure, the ageostrophic mean horizontal current, and the turbulence in the ocean surface boundary layer all change with the relative angle among the wind and the front. The net heating and cooling of the boundary layer could be explained by the depth-integrated horizontal advective buoyancy flux, called the Ekman Buoyancy Flux (or the Ekman-Stokes Buoyancy Flux if wave effects are included). However, the detailed temperature profiles are also modulated by the depth-dependent advective buoyancy flux and submesoscale eddies. The surface current is deflected less (more) to the right of the wind and wave when the depth-integrated advective buoyancy flux cools (warms) the ocean surface boundary layer. Horizontal mixing is greatly enhanced by submesoscale eddies. The eddy-induced horizontal mixing is anisotropic and is stronger to the right of the wind direction. Vertical turbulent mixing depends on the superposition of the geostrophic and ageostrophic current, the depth-dependent advective buoyancy flux, and submesoscale eddies.

scholarly journals The Contribution of Surface and Submesoscale Processes to Turbulence in the Open Ocean Surface Boundary Layer

2019 ◽  
Vol 11 (12) ◽  
pp. 4066-4094 ◽  
Author(s):  
Christian E. Buckingham ◽  
Natasha S. Lucas ◽  
Stephen E. Belcher ◽  
Tom P. Rippeth ◽  
Alan L. M. Grant ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ocean Surface ◽  
Open Ocean ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Submesoscale Processes

scholarly journals Observations of Turbulence in the Ocean Surface Boundary Layer: Energetics and Transport

2009 ◽  
Vol 39 (5) ◽  
pp. 1077-1096 ◽  
Author(s):  
Gregory P. Gerbi ◽  
John H. Trowbridge ◽  
Eugene A. Terray ◽  
Albert J. Plueddemann ◽  
Tobias Kukulka
Keyword(s):  
Boundary Layer ◽  
Diffusion Coefficient ◽  
Kinetic Energy ◽  
Wave Breaking ◽  
Ocean Surface ◽  
Surface Boundary ◽  
Langmuir Turbulence ◽  
Rigid Boundary ◽  
Surface Boundary Layer ◽  
Buoyancy Forcing

Abstract Observations of turbulent kinetic energy (TKE) dynamics in the ocean surface boundary layer are presented here and compared with results from previous observational, numerical, and analytic studies. As in previous studies, the dissipation rate of TKE is found to be higher in the wavy ocean surface boundary layer than it would be in a flow past a rigid boundary with similar stress and buoyancy forcing. Estimates of the terms in the turbulent kinetic energy equation indicate that, unlike in a flow past a rigid boundary, the dissipation rates cannot be balanced by local production terms, suggesting that the transport of TKE is important in the ocean surface boundary layer. A simple analytic model containing parameterizations of production, dissipation, and transport reproduces key features of the vertical profile of TKE, including enhancement near the surface. The effective turbulent diffusion coefficient for heat is larger than would be expected in a rigid-boundary boundary layer. This diffusion coefficient is predicted reasonably well by a model that contains the effects of shear production, buoyancy forcing, and transport of TKE (thought to be related to wave breaking). Neglect of buoyancy forcing or wave breaking in the parameterization results in poor predictions of turbulent diffusivity. Langmuir turbulence was detected concurrently with a fraction of the turbulence quantities reported here, but these times did not stand out as having significant differences from observations when Langmuir turbulence was not detected.

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