On the response of the Lorenz energy cycle for the Southern Ocean to intensified westerlies

2017 ◽  
Vol 122 (3) ◽  
pp. 2465-2493 ◽  
Author(s):  
Yang Wu ◽  
Zhaomin Wang ◽  
Chengyan Liu
Keyword(s):  
Southern Ocean ◽  
Energy Cycle ◽  
Lorenz Energy Cycle

The Lorenz Energy Cycle: Trends and the Impact of Modes of Climate Variability

2021 ◽  
Author(s):  
Qiyun Ma ◽  
Valerio Lembo ◽  
Christian Franzke
Keyword(s):  
Kinetic Energy ◽  
Climate Variability ◽  
Potential Energy ◽  
Atmospheric Circulation ◽  
Southern Hemisphere ◽  
Transient Eddy ◽  
Energy Cycle ◽  
Conversion Rates ◽  
Lorenz Energy Cycle ◽  
Modes Of Climate Variability

<p>The atmospheric circulation is driven by heat transport from the tropics to the polar regions, implying energy conversions between available potential and kinetic energy through various mechanisms. The processes of energy transformations can be quantitatively investigated in the global climate system through the Lorenz energy cycle formalism. In this study, we examine these variations and the impacts of modes of climate variability on the Lorenz energy cycle by using reanalysis data from the Japanese Meteorological Agency (JRA-55). We show that the atmospheric circulation is overall becoming more energetic and efficient. For instance, we find a statistically significant trend in the eddy available potential energy, especially in the transient eddy available potential energy in the Southern Hemisphere. We find significant trends in the conversion rates between zonal available potential and kinetic energy, consistent with an expansion of the Hadley cell, and in the conversion rates between eddy available potential and kinetic energy, suggesting an increase in mid-latitudinal baroclinic instability. We also show that planetary-scale waves dominate the stationary eddy energy, while synoptic-scale waves dominate the transient eddy energy with a significant increasing trend. Our results suggest that interannual variability of the Lorenz energy cycle is determined by modes of climate variability. We find that significant global and hemispheric energy fluctuations are caused by the El Nino-Southern Oscillation, the Arctic Oscillation, the Southern Annular Mode, and the meridional temperature gradient over the Southern Hemisphere.</p>

Energetics of the Climate System

2019 ◽  
Author(s):  
Jin-Song von Storch
Keyword(s):  
Kinetic Energy ◽  
General Circulation ◽  
General Circulation Models ◽  
Eddy Kinetic Energy ◽  
Energy Cycle ◽  
Lorenz Energy Cycle ◽  
The Mean ◽  
Realistic Data ◽  
Mean Kinetic Energy ◽  
Energy Pathways

The energetics considerations based on Lorenz’s available potential energy A focus on identification and quantification of processes capable of converting external energy sources into the kinetic energy of atmospheric and oceanic general circulations. Generally, these considerations consist of: (a) identifying the relevant energy compartments from which energy can be converted against friction to kinetic energy of motions of interests; (b) formulating for these energy compartments budget equations that describe all possible energy pathways; and (c) identifying the dominant energy pathways using realistic data. In order to obtain a more detailed description of energy pathways, a partitioning of motions, for example, into a “mean” and an “eddy” component, or into a diabatic and an adiabatic component, is used. Since the budget equations do not always suggest the relative importance of all possible pathways, often not even the directions, data that describe the atmospheric and the oceanic state in a sufficiently accurate manner are needed for evaluating the energy pathways. Apart from the complication due to different expressions of A, ranging from the original definition by Lorenz in 1955 to its approximations and to more generally defined forms, one has to balance the complexity of the respective budget equations that allows the evaluation of more possible energy pathways, with the quality of data available that allows sufficiently accurate estimates of energy pathways. With regard to the atmosphere, our knowledge, as inferred from the four-box Lorenz energy cycle, has consolidated in the last two decades, by, among other means, using data assimilation products obtained by combining observations with realistic atmospheric general circulation models (AGCMs). The eddy kinetic energy, amounting to slightly less than 50% of the total kinetic energy, is supported against friction through a baroclinic pathway “fueled” by the latitudinally dependent diabatic heating. The mean kinetic energy is supported against friction by converting eddy kinetic energy via inverse cascades. For the ocean, our knowledge is still emerging. The description through the four-box Lorenz energy cycle is approximative and was only estimated from a simulation of a 0.1° oceanic general circulation models (OGCM) realistically forced at the sea surface, rather than from a data assimilation product. The estimates obtained so far suggest that the oceanic eddy kinetic energy, amounting almost 75% of the total oceanic kinetic energy, is supported against friction through a baroclinic pathway similar to that in the atmosphere. However, the oceanic baroclinic pathway is “fueled” to a considerable extent by converting mean kinetic energy supported by winds into mean available potential energy. Winds are also the direct source of the kinetic energy of the mean circulation, without involving noticeable inverse cascades from transients, at least not for the ocean as a whole. The energetics of oceanic general circulation can also be examined by separating diabatic from adiabatic processes. Such a consideration is thought to be more appropriate for understanding the energetics of the oceanic meridional overturning circulation (MOC), since this circulation is sensitive to density changes induced by diabatic mixing. Further work is needed to quantify the respective energy pathways using realistic data.

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

2019 ◽  
Author(s):  
Valerio Lembo ◽  
Frank Lunkeit ◽  
Valerio Lucarini
Keyword(s):  
Entropy Production ◽  
Energy Budget ◽  
Diagnostic Tool ◽  
Hydrological Cycle ◽  
Heat Fluxes ◽  
Climate System ◽  
Irreversible Processes ◽  
Energy Budgets ◽  
Energy Cycle ◽  
Lorenz Energy Cycle

Abstract. This work presents Thermodynamic Diagnostic Tool (TheDiaTo), 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 these diagnostics has been developed as part of the Earth System Model eValuation Tool (ESMValTool) v2.0a1, in order to assess the performances of CMIP6 model simulations, and will be available in the next release of the tool. The aim of this software is to provide a comprehensive picture of the thermodynamics of the climate system as reproduced in the state-of-the-art coupled general circulation models. This can prove useful for better understanding anthropogenic and natural climate change, paleoclimatic climate variability, and climatic tipping points.

scholarly journals Sensitivity of the Upper Mesosphere to the Lorenz Energy Cycle of the Troposphere

2009 ◽  
Vol 66 (3) ◽  
pp. 647-666 ◽  
Author(s):  
Erich Becker
Keyword(s):  
Kinetic Energy ◽  
Gravity Wave ◽  
General Circulation ◽  
Frictional Heating ◽  
Lower Thermosphere ◽  
Wave Drag ◽  
Wind Component ◽  
Mesopause Region ◽  
Energy Cycle ◽  
Lorenz Energy Cycle

Abstract The concept of a mechanistic general circulation model that explicitly simulates the gravity wave drag in the extratropical upper mesosphere in a self-consistent fashion is proposed. The methodology consists of 1) a standard spectral dynamical core with high resolution, 2) idealized formulations of radiative and latent heating, and 3) a hydrodynamically consistent turbulent diffusion scheme with the diffusion coefficients based on Smagorinsky’s generalized mixing-length formulation and scaled by the Richardson criterion. The model reproduces various mean and variable features of the wave-driven general circulation from the boundary layer to the mesopause region during January. The dissipation of mesoscale kinetic energy (defined as the frictional heating due to the mesoscale flow) in the extratropical troposphere is found to indicate the tropospheric gravity wave sources relevant for the mesosphere/lower thermosphere. This motivates a sensitivity experiment in which the large-scale differential heating is perturbed such that the Lorenz energy cycle as measured by the globally integrated frictional heating becomes stronger. As a result, both the resolved gravity wave activity and the dissipation of mesoscale kinetic energy in the extratropical troposphere are amplified. These changes have strong remote effects in the summer mesopause region, where the gravity wave drag, the residual meridional wind, and the frictional heating shift to lower altitudes. Furthermore, temperatures decrease below the summer mesopause and increase farther up, which is accompanied by an anomalous eastward wind component around the mesopause.

scholarly journals Energy Conversion Routes in the Western Mediterranean Sea Estimated from Eddy–Mean Flow Interactions

2019 ◽  
Vol 49 (1) ◽  
pp. 247-267 ◽  
Author(s):  
Esther Capó ◽  
Alejandro Orfila ◽  
Evan Mason ◽  
Simón Ruiz
Keyword(s):  
Energy Conversion ◽  
Mediterranean Sea ◽  
Western Mediterranean ◽  
Mean Flow ◽  
Physical Mechanisms ◽  
Western Mediterranean Sea ◽  
Energy Cycle ◽  
Flow Interactions ◽  
Lorenz Energy Cycle ◽  
The Mean

AbstractEnergy conversion routes are investigated in the western Mediterranean Sea from the eddy–mean flow interactions. The sources of eddy kinetic energy are analyzed by applying a regional formulation of the Lorenz energy cycle to 18 years of numerical simulation at eddy-resolving resolution (3.5 km), which allows for identifying whether the energy exchange between the mean and eddy flow is local or nonlocal. The patterns of energy conversion between the mean and eddy kinetic and potential energy are estimated in three subregions of the domain: the Alboran Sea, the Algerian Basin, and the northern basin. The spatial characterization of the energy routes hints at the physical mechanisms involved in maintaining the balance, suggesting that flow–topography interaction is strongly linked to eddy growth in most of the domain.

scholarly journals Thermodynamics of climate change: generalized sensitivities

2010 ◽  
Vol 10 (20) ◽  
pp. 9729-9737 ◽  
Author(s):  
V. Lucarini ◽  
K. Fraedrich ◽  
F. Lunkeit
Keyword(s):  
Entropy Production ◽  
Climate Models ◽  
Climate Model ◽  
Co2 Concentration ◽  
Heat Fluxes ◽  
Predominant Role ◽  
Energy Cycle ◽  
Wide Range ◽  
Linear Behaviour ◽  
Lorenz Energy Cycle

Abstract. Using a recent theoretical approach, we study how global warming impacts the thermodynamics of the climate system by performing experiments with a simplified yet Earth-like climate model. The intensity of the Lorenz energy cycle, the Carnot efficiency, the material entropy production, and the degree of irreversibility of the system change monotonically with the CO2 concentration. Moreover, these quantities feature an approximately linear behaviour with respect to the logarithm of the CO2 concentration in a relatively wide range. These generalized sensitivities suggest that the climate becomes less efficient, more irreversible, and features higher entropy production as it becomes warmer, with changes in the latent heat fluxes playing a predominant role. These results may be of help for explaining recent findings obtained with state of the art climate models regarding how increases in CO2 concentration impact the vertical stratification of the tropical and extratropical atmosphere and the position of the storm tracks.

scholarly journals The impact of oceanic heat transport on the atmospheric circulation

2014 ◽  
Vol 5 (2) ◽  
pp. 1463-1490
Author(s):  
M.-A. Knietzsch ◽  
V. Lucarini ◽  
F. Lunkeit
Keyword(s):  
Potential Energy ◽  
Heat Transport ◽  
Atmospheric Circulation ◽  
General Circulation ◽  
Hadley Cell ◽  
Oceanic Heat Transport ◽  
Energy Cycle ◽  
Lorenz Energy Cycle ◽  
The Impact ◽  
Global Mean

Abstract. A general circulation model of intermediate complexity with an idealized earthlike aquaplanet setup is used to study the impact of changes in the oceanic heat transport on the global atmospheric circulation. Focus is put on the Lorenz energy cycle and the atmospheric mean meridional circulation. The latter is analysed by means of the Kuo–Eliassen equation. The atmospheric heat transport compensates the imposed oceanic heat transport changes to a large extent in conjunction with significant modification of the general circulation. Up to a maximum about 3 PW, an increase of the oceanic heat transport leads to an increase of the global mean near-surface temperature and a decrease of its equator-to-pole gradient. For larger transports, the gradient is reduced further but the global mean remains approximately constant. This is linked to a cooling and a reversal of the temperature gradient in the tropics. A larger oceanic heat transport leads to a reduction of all reservoirs and conversions of the Lorenz energy cycle but of different relative magnitude for the individual components. The available potential energy of the zonal mean flow and its conversion to eddy available potential energy are affected most. Both the Hadley and Ferrel cell show a decline for increasing oceanic heat transport, with the Hadley cell being more sensitive. Both cells exhibit a poleward shift of their maxima, and the Hadley cell broadens for larger oceanic transports. The partitioning, by means of the Kuo–Eliassen equation, reveals that zonal mean diabatic heating and friction are the most important sources for changes of the Hadley cell, while the behaviour of the Ferrell cell is mostly controlled by friction.

Diagnosing mixing in stratified turbulent flows with a locally defined available potential energy

2014 ◽  
Vol 740 ◽  
pp. 114-135 ◽  
Author(s):  
Alberto Scotti ◽  
Brian White
Keyword(s):  
Potential Energy ◽  
Turbulent Flows ◽  
Boussinesq Approximation ◽  
Mixing Efficiency ◽  
Available Potential Energy ◽  
Energy Cycle ◽  
Lorenz Energy Cycle ◽  
The Mean ◽  
Definition Of ◽  
Special Circumstances

AbstractA local available potential energy (APE) density useful as suitable diagnostic tool in turbulent stratified flows is considered under the Boussinesq approximation. The local APE is positive, and in the limit of infinitesimal perturbation from an equilibrium state recovers the Lorenz energy cycle definition of APE. In a turbulent stratified flow, the APE can be Reynolds-decomposed into non-trivial mean and turbulent components, which are connected to the mean and turbulent kinetic energy by suitably defined fluxes. We show that the turbulent buoyancy flux $\overline{w'b'}$ and the rate of production of turbulent APE coincide only under very special circumstances. The framework is applied to derive some global bounds on the mixing efficiency of some representative flows.

scholarly journals Thermodynamics of climate change: generalized sensitivities

2010 ◽  
Vol 10 (2) ◽  
pp. 3699-3715 ◽  
Author(s):  
V. Lucarini ◽  
K. Fraedrich ◽  
F. Lunkeit
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Surface Temperature ◽  
Entropy Production ◽  
Theoretical Approach ◽  
Climate Model ◽  
Co2 Concentration ◽  
Energy Cycle ◽  
Lorenz Energy Cycle ◽  
The Impact

Abstract. Using a recent theoretical approach, we study how the impact of global warming of the thermodynamics of the climate system by performing experiments with a simplified yet Earth-like climate model. In addition to the globally averaged surface temperature, the intensity of the Lorenz energy cycle, the Carnot efficiency, the material entropy production and the degree of irreversibility of the system are linear with the logarithm of the CO2 concentration. These generalized sensitivities suggest that the climate becomes less efficient, more irreversible, and features higher entropy production as it becomes warmer.

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