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Simulating Real Atmospheric Boundary Layers at Gray-Zone Resolutions: How Do Currently Available Turbulence Parameterizations Perform?

A Budget-Based Turbulence Length Scale Diagnostic

Faculty of Geosciences and Geography, Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(4), 425;
Received: 27 February 2020 / Revised: 11 April 2020 / Accepted: 17 April 2020 / Published: 22 April 2020
The most frequently used boundary-layer turbulence parameterization in numerical weather prediction (NWP) models are turbulence kinetic energy (TKE) based-based schemes. However, these parameterizations suffer from a potential weakness, namely the strong dependence on an ad-hoc quantity, the so-called turbulence length scale. The physical interpretation of the turbulence length scale is difficult and hence it cannot be directly related to measurements or large eddy simulation (LES) data. Consequently, formulations for the turbulence length scale in basically all TKE schemes are based on simplified assumptions and are model-dependent. A good reference for the independent evaluation of the turbulence length scale expression for NWP modeling is missing. Here we propose a new turbulence length scale diagnostic which can be used in the gray zone of turbulence without modifying the underlying TKE turbulence scheme. The new diagnostic is based on the TKE budget: The core idea is to encapsulate the sum of the molecular dissipation and the cross-scale TKE transfer into an effective dissipation, and associate it with the new turbulence length scale. This effective dissipation can then be calculated as a residuum in the TKE budget equation (for horizontal sub-domains of different sizes) using LES data. Estimation of the scale dependence of the diagnosed turbulence length scale using this novel method is presented for several idealized cases. View Full-Text
Keywords: turbulence length scale; gray zone of turbulence; large eddy simulation turbulence length scale; gray zone of turbulence; large eddy simulation
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MDPI and ACS Style

Bašták Ďurán, I.; Schmidli, J.; Bhattacharya, R. A Budget-Based Turbulence Length Scale Diagnostic. Atmosphere 2020, 11, 425.

AMA Style

Bašták Ďurán I, Schmidli J, Bhattacharya R. A Budget-Based Turbulence Length Scale Diagnostic. Atmosphere. 2020; 11(4):425.

Chicago/Turabian Style

Bašták Ďurán, Ivan, Juerg Schmidli, and Ritthik Bhattacharya. 2020. "A Budget-Based Turbulence Length Scale Diagnostic" Atmosphere 11, no. 4: 425.

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