Abstract

In this study, shear-based parameterizations of turbulent mixing in the stable atmospheric boundary layer (SABL) are proposed. A relevant length-scale estimate for the mixing length LM of the turbulent momentum field is constructed from the turbulent kinetic energy Ek and the mean shear rate S as. Using observational data from two field campaigns-the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment and the 1999 Cooperative Atmosphere-Surface Exchange Study (CASES-99)- is shown to have a strong correlation with LM. The relationship between LM and corresponds to the ratio of the magnitude of the tangential components of the turbulent momentum flux tensor τ to Ek, known as stress intensity ratio, c2 = τ/Ek. The field data clearly show that c2 is linked to stability. The stress intensity ratio also depends on the flow energetics that can be assessed using a shear-production Reynolds number, ReSP = P/(vS2), where P is shear production of turbulent kinetic energy and ν is the kinematic viscosity. This analysis shows that high mixing rates can indeed persist at strong stability. On this basis, shear-based parameterizations are proposed for the eddy diffusivity for momentum, KM, and eddy diffusivity for heat, KH, showing remarkable agreement with the exact quantities. Furthermore, a broader assessment of the proposed parameterizations is given through an a priori evaluation of large-eddy simulation (LES) data from the first GEWEX Atmospheric Boundary Layer Study (GABLS). The shear-based parameterizations outperform many existing models in predicting turbulent mixing in the SABL. The results of this study provide a framework for improved representation of the SABL in operational models.

Department(s)

Civil, Architectural and Environmental Engineering

Publication Status

Full Access

Keywords and Phrases

Boundary layer; Diapycnal mixing; Fluxes; Mixing; Parameterization; Small scale processes

International Standard Serial Number (ISSN)

1520-0469; 0022-4928

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2025 American Meteorological Society, All rights reserved.

Publication Date

01 Jan 2015

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