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An Extended Eddy-Diffusivity Mass-Flux Scheme for Unified Representation of Subgrid-Scale Turbulence and Convection

Tan, Zhihong and Kaul, Colleen M. and Pressel, Kyle G. and Cohen, Yair and Schneider, Tapio and Teixeira, João (2018) An Extended Eddy-Diffusivity Mass-Flux Scheme for Unified Representation of Subgrid-Scale Turbulence and Convection. Journal of Advances in Modeling Earth Systems, 10 (3). pp. 770-800. ISSN 1942-2466.

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Large-scale weather forecasting and climate models are beginning to reach horizontal resolutions of kilometers, at which common assumptions made in existing parameterization schemes of subgrid-scale turbulence and convection—such as that they adjust instantaneously to changes in resolved-scale dynamics—cease to be justifiable. Additionally, the common practice of representing boundary-layer turbulence, shallow convection, and deep convection by discontinuously different parameterizations schemes, each with its own set of parameters, has contributed to the proliferation of adjustable parameters in large-scale models. Here we lay the theoretical foundations for an extended eddy-diffusivity mass flux (EDMF) scheme that has explicit time-dependence and memory of subgrid-scale variables and is designed to represent all subgrid-scale turbulence and convection, from boundary layer dynamics to deep convection, in a unified manner. Coherent up- and downdrafts in the scheme are represented as prognostic plumes that interact with their environment and potentially with each other through entrainment and detrainment. The more isotropic turbulence in their environment is represented through diffusive fluxes, with diffusivities obtained from a turbulence kinetic energy budget that consistently partitions turbulence kinetic energy between plumes and environment. The cross-sectional area of up- and downdrafts satisfies a prognostic continuity equation, which allows the plumes to cover variable and arbitrarily large fractions of a large-scale grid box and to have life cycles governed by their own internal dynamics. Relatively simple preliminary proposals for closure parameters are presented and are shown to lead to a successful simulation of shallow convection, including a time-dependent life cycle.

Item Type:Article
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URLURL TypeDescription
Tan, Zhihong0000-0002-7422-3317
Kaul, Colleen M.0000-0002-4462-0987
Pressel, Kyle G.0000-0002-4538-3055
Cohen, Yair0000-0002-9615-2476
Schneider, Tapio0000-0001-5687-2287
Additional Information:© 2018. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Received 1 SEP 2017; Accepted 1 FEB 2018; Accepted article online 6 FEB 2018; Published online 23 MAR 2018. This work was supported by the U.S. National Science Foundation (grant CCF-1048575), by Caltech's Terrestrial Hazard Observation and Reporting (THOR) Center, by the Swiss National Science Foundation (grant 200021 156109), and by the President's and Director's Fund of Caltech and the Jet Propulsion Laboratory. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration and funded through the internal Research and Technology Development program. JT acknowledges the support of the NASA MAP Program. The numerical simulations were performed on the Euler Cluster operated by the high-performance computing (HPC) team at ETH Züurich. The PyCLES codes used to generate results in this paper is available at We thank Wolfgang Langhans for very helpful comments on an earlier version of this paper. Author Contributions: T.S. and J.T. conceived the project. Z.T., T.S., and K.G.P. developed the theoretical framework. C.M.K. developed the single-column model, its numerical discretization, and some closures in it, based on a prototype by Z.T. K.G.P. carried out the LES, and C.M.K. and Y.C. carried out the single-column model tests. Z.T. and T.S. led the writing of the paper, with all authors contributing.
Funding AgencyGrant Number
Caltech Terrestrial Hazard Observation and Reporting (THOR) CenterUNSPECIFIED
Swiss National Science Foundation (SNSF)200021_156109
JPL President and Director's FundUNSPECIFIED
Subject Keywords:Turbulence; Convection; Parameterization; Eddy diffusivity/mass flux scheme; Climate modeling
Record Number:CaltechAUTHORS:20180206-095908216
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Official Citation:Tan, Z., Kaul, C. M., Pressel, K. G., Cohen, Y., Schneider, T., & Teixeira, J. (2018). An extended eddy‐diffusivity mass‐flux scheme for unified representation of subgrid‐scale turbulence and convection. Journal of Advances in Modeling Earth Systems, 10, 770–800.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84683
Deposited By: Tony Diaz
Deposited On:06 Feb 2018 18:52
Last Modified:26 Apr 2018 15:02

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