Journal
BOUNDARY-LAYER METEOROLOGY
Volume 146, Issue 3, Pages 341-373Publisher
SPRINGER
DOI: 10.1007/s10546-012-9768-8
Keywords
Boundary layers; Critical Richardson number; Eddy viscosity; Conductivity; Diffusivity; Free atmosphere; Inter-component kinetic energy exchange; Kinetic potential and total turbulent energiesMonin-Obukhov similarity theory; Stability parameters; Stable stratification; Turbulence closure; Turbulent fluxes; Turbulent dissipation time and length scales
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Funding
- EC FP7 ERC [227915]
- Russian Federation Government [11.G34.31.0048]
- Israel Science Foundation governed by the Israeli Academy of Sciences [259/07, 1037/11]
- Norwegian Research Council [191516/V30]
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Here we advance the physical background of the energy-and flux-budget turbulence closures based on the budget equations for the turbulent kinetic and potential energies and turbulent fluxes of momentum and buoyancy, and a new relaxation equation for the turbulent dissipation time scale. The closure is designed for stratified geophysical flows from neutral to very stable and accounts for the Earth's rotation. In accordance with modern experimental evidence, the closure implies the maintaining of turbulence by the velocity shear at any gradient Richardson number Ri, and distinguishes between the two principally different regimes: strong turbulence at Ri << 1 typical of boundary-layer flows and characterized by the practically constant turbulent Prandtl number Pr-T; and weak turbulence at Ri > 1 typical of the free atmosphere or deep ocean, where Pr-T asymptotically linearly increases with increasing Ri ( which implies very strong suppression of the heat transfer compared to the momentum transfer). For use in different applications, the closure is formulated at different levels of complexity, from the local algebraic model relevant to the steady-state regime of turbulence to a hierarchy of non-local closures including simpler down-gradient models, presented in terms of the eddy viscosity and eddy conductivity, and a general non-gradient model based on prognostic equations for all the basic parameters of turbulence including turbulent fluxes.
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