Abstract:

The dataset is a collection of idealized oceanic simulations; the fluxes and vertical gradients of tracers are used to estimate the eddy-diffusivity for a variety of regimes instability/Langmuir number space, including wind, convection, and Langmuir-dominated conditions. A large eddy simulation (LES) model generates vertical profiles of fluxes which allow the exploration of a new approach to specifying diffusive and nondiffusive contributions to the vertical eddy diffusivity without specifying shape or scale. Diffusivities, fluxes, and shapes are provided for surface and entrainment dominated fluxes.

Suggested Citation:

Chor, Tomas. 2020. Modifications of the K-Profile parameterization by diffusive/nondiffusive flux separation in ocean mixed layers including wave effects. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/JRFXRNA9

Publications:

Chor, T., McWilliams, J. C., & Chamecki, M. (2021). Modifications to the K-Profile Parameterization with Nondiffusive Fluxes for Langmuir Turbulence. Journal of Physical Oceanography, 51(5), 1503–1521. doi:10.1175/jpo-d-20-0250.1

Purpose:

To investigate the vertical mixing of tracers in models of the ocean boundary layer by estimating diffusive and nondiffusive fluxes in a wave-filled environment without a priori assumptions of shape or scaling.

Data Parameters and Units:

The dataset consists of a README file; “overall_atm.nc”, which details the ratio of nondiffusive to total fluxes and the ratio of bulk velocity scale to bulk velocity scale in Troen and Mahrt, 1983; and thirteen files specifying profiles of fluxes, diffusivities, and shape functions for the stability/Langmuir number parameter space, which includes regimes dominated by wind, convection, and Langmuir. The profile data files have the parameters wc (vertical turbulent flux of tracers, [m/s]); dCdz (mean vertical tracer gradient, [m/s]); Fd_opt (turbulent diffusive flux of tracers, [m/s]); Fnd_op (turbulent nondiffusive flux of tracers, [m/s]); K_opt (eddy diffusivity from optimized method, [m^2/s]); K_liter (eddy diffusivity curves derived from the literature); Gs_opt (surface-driven nondiffusive flux shape function from optimization, [dimensionless]); Ge_opt (entrainment-driven nondiffusive flux shape function from optimization, [dimensionless]); Gs_liter (surface-driven nondiffusive flux shape function derived from the literature); z (depth normalized by the depth of the boundary layer, [dimensionless]); Λ (stability parameter, w*^3/u*^3 = -κ z_e / L_o, [dimensionless]); wcs (tracer flux at surface, [m/s]); wce (tracer flux at entrainment, [m/s]); u_star_meas (measured friction velocity, [m/s]); w_star_meas (measured convective velocity, [m/s]); he_meas (measured depth of maximum entrainment, [m]); h (measured depth of boundary layer, [m]); L_o (Monin-Obukhov length, [m]). The bulk ratios file has RF (ratio of nondiffusive to total fluxes); La_t (turbulent Langmuir number, [nondimensional]), Λ (stability parameter, w_^3/u_^3, [nondimensional]), z [nondimensional], and enhancement factors. The final file contains the base averaged shape functions derived in this work; parameters are z, G_l (shape function of eddy diffusivity in Langmuir-dominated regimes), and Gs (shape function for surface-driven nondiffusive transport). All are nondimensional.

Methods:

Large-eddy simulation (LES) model-produced vertical fluxes of passive tracers and temperature were used to explore the diffusive/nondiffusive decomposition of vertical eddy diffusivity profiles. Nine simulations are presented. The LES model domain is 400 x 400 x 250 m with 256 grid points in the horizontal directions and 400 gridpoints in the vertical. A sponge layer in the bottom one-quarter of the domain provides an open boundary, horizontal boundary conditions are periodic, and a Stokes drift profile imposes monochromatic wave effects for each simulation. Different amounts of cooling and wind stress at the surface and waves of different characteristics provide the top boundary conditions. All simulations were tested to ensure that the resolution was fine enough to resolve the important eddies for vertical mixing and the Stokes drift shear in the (OSBL). All simulations also contain two separate tracers with sources at the surface (SFT) and from entrainment processes (EFT) and potential temperature. Further details may be found in the associated publication, currently in review: Chor, T., McWilliams, J. C., & Chamecki, M. Modifications of the K-Profile parameterization with nondiffusive fluxes for wave effects.

Individual Files: