How is local material entropy production represented in a numerical model?

Gaßmann, Almut; Herzog, H. Jürgen

doi:10.1002/qj.2404

Cited by 29 publications

(58 citation statements)

References 46 publications

(67 reference statements)

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“…Then internal entropy production becomes negative. This observation has been made by several authors (Goody, ; Romps, ; Gassmann and Herzog, ).…”

Section: Energy‐ and Entropy‐compliant Subgrid‐scale Fluxessupporting

confidence: 71%

“…The second law of thermodynamics states d S i ≥0, but does not make any statement about d S e , which might have either sign. In a recent paper, Gassmann and Herzog () analyzed the different entropy source terms (apart from radiation) in contemporary model formulations and confirmed the current knowledge (Goody, ; Romps, ; Raymond, ) that the formulation of vertical heat fluxes reveals negative internal entropy production in the case of stable stratification, whereas the unstable case is unproblematic. This failure in the case of stable stratification is supposed to become especially important for predominantly mechanically driven turbulence, as is the case for gravity wave breaking in the mesosphere.…”

Section: Introductionmentioning

confidence: 62%

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Entropy production due to subgrid‐scale thermal fluxes with application to breaking gravity waves

Gaßmann

2018

Quart J Royal Meteoro Soc

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Numerical formulations of turbulent heat fluxes must lead to positive energy dissipation of energy contained in the resolved scales and positive internal entropy production. Current parametrization approaches deliver positive dissipation rates only for free convection, not for forced convection. This contribution explains how positive dissipation rates are achieved by a new formulation of subgrid-scale terms in the case of stable stratification. This is of importance for the numerical realization of the breakdown of gravity waves. A turbulent atmosphere tends to an isentropic stratification, because in addition to turbulent heat diffusion, pressure work leads to expansion when air is rising and contraction when air is sinking. This pressure work remains completely subgrid-scale when the atmosphere is unstably stratified. When the atmosphere is stably stratified, this pressure work has to be done by the outer environment. Therefore, a turbulent pressure gradient term is introduced in the vertical momentum equation and the equations account for the irreversible energy conversion from resolved kinetic energy into the model's internal energy. Numerical experiments for breaking gravity waves in the mesosphere highlight the different behaviour of new and conventional approaches. The conventional approach leads to a deepening of the wave amplitudes, whereas the new approach supports wave overturning. The observed foliate structure of very sharp inversion layers is indeed simulated with the new approach for stable stratification. In contrast to the traditional setting, the new scheme does not evolve into persistent non-physical wave structures on long time-scales. The term unavailable is here meant in its original physical sense, not in the meteorological sense. Making energy unavailable means that a further reversible energy conversion is no longer possible.c 2017 Royal Meteorological Society † Note:

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“…Then internal entropy production becomes negative. This observation has been made by several authors (Goody, ; Romps, ; Gassmann and Herzog, ).…”

Section: Energy‐ and Entropy‐compliant Subgrid‐scale Fluxessupporting

confidence: 71%

Section: Introductionmentioning

confidence: 62%

Entropy production due to subgrid‐scale thermal fluxes with application to breaking gravity waves

Gaßmann

2018

Quart J Royal Meteoro Soc

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“…Given the multiscale properties of the climate system, accurate energy and entropy budgets are affected by subgrid-scale parametrizations (see also Kleidon and Lorenz (2004); Kunz et al (2008)). These and the discretization of the numerical scheme are generally problematic in terms of conservation principles (Gassmann and Herzog, 2015), and can eventually lead to macroscopic model drifts (Mauritsen et al, 2012;Gupta et al, 2013;Hobbs et al, 2016;Hourdin et al, 2017). See Lucarini and Fraedrich (2009) for a theoretical analysis in a simplified setting.…”

Section: Entropymentioning

confidence: 99%

TheDiaTo (v1.0) – a new diagnostic tool for water, energy and entropy budgets in climate models

Lembo¹,

Lunkeit²,

Lucarini

2019

Geosci. Model Dev.

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This work presents a novel diagnostic tool for studying the thermodynamics of the climate systems with a wide range of applications, from sensitivity studies to model tuning. It includes a number of modules for assessing the internal energy budget, the hydrological cycle, the Lorenz Energy Cycle and the material entropy production, respectively. The routine receives as inputs energy fluxes at surface and at the Top-of-Atmosphere (TOA), for the computation of energy budgets at Top-of-Atmosphere (TOA), at the surface, and in the atmosphere as a residual. Meridional enthalpy transports are also computed from the divergence of the zonal mean energy budget fluxes; location and intensity of peaks in the two hemispheres are then provided as outputs. Rainfall, snowfall and latent heat fluxes are received as inputs for computing the water mass and latent energy budgets. If a land-sea mask is provided, the required quantities are separately computed over continents and oceans. The diagnostic tool also computes the Lorenz Energy Cycle (LEC) and its storage/conversion terms as annual mean global and hemispheric values. In order to achieve this, one needs to provide as input three-dimensional daily fields of horizontal wind velocity and temperature in the troposphere. Two methods have been implemented for the computation of the material entropy production, one relying on the convergence of radiative heat fluxes in the atmosphere (indirect method), one combining the irreversible processes occurring in the climate system, particularly heat fluxes in the boundary layer, the hydrological cycle and the kinetic energy dissipation as retrieved from the residuals of the LEC. A version of the diagnostic tool is included in the Earth System Model eValuation Tool (ESMValTool) community diagnostics, in order to assess the performances of soon available

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“…The momentum diffusion coefficients K m and K u are no longer connected via a Prandtl number P r of O (1). Idealized 2D numerical experiments have been performed with the ICON-IAP model (Gassmann 2013) to contrast the second-law-compliant and second-law-violating formulations. In these, breaking gravity waves were simulated at a critical layer in the mesosphere.…”

Section: A Dry Atmospherementioning

confidence: 99%

Physics–Dynamics Coupling in Weather, Climate, and Earth System Models: Challenges and Recent Progress

Groß

Wan

Rasch

et al. 2018

Monthly Weather Review

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Numerical weather, climate, or Earth system models involve the coupling of components. At a broad level, these components can be classified as the resolved fluid dynamics, unresolved fluid dynamical aspects (i.e., those represented by physical parameterizations such as subgrid-scale mixing), and nonfluid dynamical aspects such as radiation and microphysical processes. Typically, each component is developed, at least initially, independently. Once development is mature, the components are coupled to deliver a model of the required complexity. The implementation of the coupling can have a significant impact on the model. As the error associated with each component decreases, the errors introduced by the coupling will eventually dominate. Hence, any improvement in one of the components is unlikely to improve the performance of the overall system. The challenges associated with combining the components to create a coherent model are here termed physics–dynamics coupling. The issue goes beyond the coupling between the parameterizations and the resolved fluid dynamics. This paper highlights recent progress and some of the current challenges. It focuses on three objectives: to illustrate the phenomenology of the coupling problem with references to examples in the literature, to show how the problem can be analyzed, and to create awareness of the issue across the disciplines and specializations. The topics addressed are different ways of advancing full models in time, approaches to understanding the role of the coupling and evaluation of approaches, coupling ocean and atmosphere models, thermodynamic compatibility between model components, and emerging issues such as those that arise as model resolutions increase and/or models use variable resolutions.

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How is local material entropy production represented in a numerical model?

Cited by 29 publications

References 46 publications

Entropy production due to subgrid‐scale thermal fluxes with application to breaking gravity waves

Entropy production due to subgrid‐scale thermal fluxes with application to breaking gravity waves

TheDiaTo (v1.0) – a new diagnostic tool for water, energy and entropy budgets in climate models

Physics–Dynamics Coupling in Weather, Climate, and Earth System Models: Challenges and Recent Progress

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