scholarly journals Applications of a Moist Nonhydrostatic Formulation of the Spectral Energy Budget to Baroclinic Waves. Part I: The Lower-Stratospheric Energy Spectra

2015 ◽  
Vol 72 (5) ◽  
pp. 2090-2108 ◽  
Author(s):  
Jun Peng ◽  
Lifeng Zhang ◽  
Jiping Guan
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Budget ◽  
Vertical Flux ◽  
Energy Spectra ◽  
Spectral Energy ◽  
Positive Contribution ◽  
Flux Divergence ◽  
Available Potential Energy ◽  
Baroclinic Waves

Abstract The authors investigate the mesoscale dynamics that produce the lower-stratospheric energy spectra in idealized moist baroclinic waves, using the moist nonhydrostatic formulation of spectral energy budget of kinetic energy and available potential energy by J. Peng et al. The inclusion of moist processes energizes the lower-stratospheric mesoscale, helping to close the gap between observed and simulated energy spectra. In dry baroclinic waves, the lower-stratospheric mesoscale is mainly forced by weak downscale cascades of both horizontal kinetic energy (HKE) and available potential energy (APE) and by a weak conversion of APE to HKE. At wavelengths less than 1000 km, the pressure vertical flux divergence also has a significant positive contribution to the HKE; however, this positive contribution is largely counteracted by the negative HKE vertical flux divergence. In moist baroclinic waves, the lower-stratospheric mesoscale HKE is mainly generated by the pressure and HKE vertical flux divergences. This additional HKE is partly converted to APE and partly removed by diffusion. Another negative contribution to the mesoscale HKE is from the forcing of a visible upscale HKE cascade. Besides the conversion of HKE, however, the three-dimensional divergence also has a significant positive contribution to the mesoscale APE. With these two direct APE sources, the lower-stratospheric mesoscale also undergoes a much stronger upscale APE cascade. These results suggest that both downscale and upscale cascades through the mesoscale are permitted in the real atmosphere and the direct forcing of the mesoscale is available to feed the upscale energy cascade.

scholarly journals Mesoscale Energy Spectra of the Mei-Yu Front System. Part II: Moist Available Potential Energy Spectra

2014 ◽  
Vol 71 (4) ◽  
pp. 1410-1424 ◽  
Author(s):  
Jun Peng ◽  
Lifeng Zhang ◽  
Yu Luo ◽  
Chunhui Xiong
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Lower Stratosphere ◽  
Vertical Flux ◽  
Energy Spectra ◽  
Spectral Energy ◽  
Positive Contribution ◽  
Spectral Slope ◽  
Upper Troposphere ◽  
Available Potential Energy

Abstract In Part II of this study, a new formulation of the spectral energy budget of moist available potential energy (MAPE) and kinetic energy is derived. Compared to previous formulations, there are three main improvements: (i) the Lorenz available potential energy is extended into a general moist atmosphere, (ii) the water vapor and hydrometeors are taken into account, and (iii) it is formulated in a nonhydrostatic framework. Using this formulation, the mesoscale MAPE spectra of the idealized mei-yu front system simulated in Part I are further analyzed. At the mature stage, the MAPE spectra in the upper troposphere and lower stratosphere also show a distinct spectral transition in the mesoscale: they develop an approximately −3 spectral slope for wavelengths longer than 400 km and − spectral slope for shorter wavelengths. In the upper troposphere, mesoscale MAPE is mainly deposited through latent heating and subsequently converted to other forms of energy at the same wavenumber. At wavelengths longer than roughly 400 km, the conversion of MAPE to horizontal kinetic energy (HKE) dominates, while at shorter wavelengths, the mechanical work produced by convective systems primarily adds to the potential energy of moist species and only secondarily generates HKE. However, this secondary conversion is enough to maintain the mesoscale − HKE spectral slope. Another positive contribution comes from the divergence term and the vertical flux. In the lower stratosphere, the main source of mesoscale MAPE is the conversion of HKE, although the vertical flux and the spectral transfer also have notable contributions.

scholarly journals Applications of a Moist Nonhydrostatic Formulation of the Spectral Energy Budget to Baroclinic Waves. Part II: The Upper-Tropospheric Energy Spectra

2015 ◽  
Vol 72 (10) ◽  
pp. 3923-3939 ◽  
Author(s):  
Jun Peng ◽  
Lifeng Zhang ◽  
Jiping Guan
Keyword(s):  
Energy Budget ◽  
Large Scale ◽  
Lower Troposphere ◽  
Gravitational Energy ◽  
Energy Spectra ◽  
Spectral Energy ◽  
Positive Contribution ◽  
Latent Heating ◽  
Baroclinic Waves ◽  
Moist Processes

Abstract In this second part of a two-part study, a newly developed moist nonhydrostatic formulation of the spectral energy budget of both kinetic energy (KE) and available potential energy (APE) is employed to investigate the dynamics underlying the mesoscale upper-tropospheric energy spectra in idealized moist baroclinic waves. By calculating the conservative nonlinear spectral fluxes, it is shown that the inclusion of moist processes significantly enhances downscale cascades of both horizontal KE and APE. Moist processes act not only as a source of latent heat but also as an “atmospheric dehumidifier.” The latent heating, mainly because of the depositional growth of cloud ice, has a significant positive contribution to mesoscale APE. However, the dehumidifying reduces the diabatic contribution of the latent heating by 15% at all scales. Including moist processes also changes the direction of the mesoscale conversion between APE and horizontal KE and adds a secondary conversion of APE to gravitational energy of moist species. With or without moisture, the vertically propagating inertia–gravity waves (IGWs) produced in the lower troposphere result in a significant positive contribution to the upper-tropospheric horizontal KE spectra at the large-scale end of the mesoscale. However, including moist processes generates additional sources of IGWs located in the upper troposphere; the upward propagation of the convectively generated IGWs removes much of the horizontal KE there. Because of the restriction of the anelastic approximation, the three-dimensional divergence has no significant contribution. In view of conflicting contributions of various direct forcings, finally, an explicit comparison between the net direct forcing and energy cascade is made.

scholarly journals Budgets of rotational and divergent kinetic energy in the warm-sector torrential rains over South China: a case study

2021 ◽  
Author(s):  
Shui-Xin Zhong ◽  
Wei-Guang Meng ◽  
Fu-You Tian
Keyword(s):  
Kinetic Energy ◽  
Energy Budget ◽  
South China ◽  
Extreme Precipitation ◽  
Flux Divergence ◽  
Low Level ◽  
Warm Sector ◽  
Kinetic Energy Budget ◽  
Rotational Components ◽  
The Pearl River

AbstractThe contributions of divergent and rotational wind components to the kinetic energy budget during a record-breaking rainstorm on 7 May 2017 over South China are examined. This warm-sector extreme precipitation caused historical maximum of 382.6 mm accumulated rainfall in 3 h over the Pearl River Delta (PRD) regions in South China. Results show that there was a high low-level southerly wind-speed tongue stretching into the PRD regions from the northeast of the South China Sea (SCS) during this extreme precipitation. The velocity potential exhibited a low-value center as well as a low-level divergence-center over the SCS. The rotational components of the kinetic energy (KR)-related terms were the main contribution-terms of the kinetic energy budget. The main contribution-terms of KR and the divergent component of kinetic energy (KD) were the barotropical and baroclinic processes-related terms due to cross-contour flow and the vertical flux divergence.

scholarly journals Investigation of Mesoscale Available Potential Energy Spectra in a Simulated Tropical Cyclone

2019 ◽  
Vol 33 (6) ◽  
pp. 1098-1112 ◽  
Author(s):  
Yuan Wang ◽  
Lifeng Zhang ◽  
Jun Peng ◽  
Yun Zhang ◽  
Tongfeng Wei
Keyword(s):  
Tropical Cyclone ◽  
Potential Energy ◽  
Energy Spectra ◽  
Available Potential Energy

Study of the Mechanisms of Vortex Variability in the Lofoten Basin Based on the Energy Analysis

2021 ◽  
Vol 37 (3) ◽  
Author(s):  
V. S. Travkin ◽  
◽  
T. V. Belonenko ◽  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Baroclinic Instability ◽  
Positive Trend ◽  
Barotropic Instability ◽  
Available Potential Energy ◽  
Conversion Rates ◽  
Order Of Magnitude ◽  
The Mean ◽  
Mean Kinetic Energy

Purpose. The Lofoten Basin is one of the most energetic zones of the World Ocean characterized by high activity of mesoscale eddies. The study is aimed at analyzing different components of general energy in the basin, namely the mean kinetic and vortex kinetic energy calculated using the integral of the volume of available potential and kinetic energy of the Lofoten Vortex, as well as variability of these characteristics. Methods and Results. GLORYS12V1 reanalysis data for the period 2010–2018 were used. The mean kinetic energy and the eddy kinetic one were analyzed; and as for the Lofoten Vortex, its volume available potential and kinetic energy were studied. The mesoscale activity of eddies in winter is higher than in summer. Evolution of the available potential energy and kinetic energy of the Lofoten Vortex up to the 1000 m horizon was studied. It is shown that the vortex available potential energy exceeds the kinetic one by an order of magnitude, and there is a positive trend with the coefficient 0,23⋅1015 J/year. It was found that in the Lofoten Basin, the intermediate layer from 600 to 900 m made the largest contribution to the potential energy, whereas the 0–400 m layer – to kinetic energy. The conversion rates of the mean kinetic energy into the vortex kinetic one and the mean available potential energy into the vortex available potential one (barotropic and baroclinic instability) were analyzed. It is shown that the first type of transformation dominates in summer, while the second one is characterized by its increase in winter. Conclusions. The vertical profile shows that the kinetic energy of eddies in winter is higher than in summer. The available potential energy of a vortex is by an order of magnitude greater than the kinetic energy. An increase in the available potential energy is confirmed by a significant positive trend and by a decrease in the vortex Burger number. The graphs of the barotropic instability conversion rate demonstrate the multidirectional flows in the vortex zone with the dipole structure observed in a winter period, and the tripole one – in summer. The barotropic instability highest intensity is observed in summer. The baroclinic instability is characterized by intensification of the regime in winter that is associated with weakening of stratification in this period owing to winter convection.

Linking surface enthalpy fluxes to the forces driving the secondary circulation: towards a causal theory of tropical cyclone intensification

2020 ◽  
Author(s):  
Remi Tailleux ◽  
Bethan Harris ◽  
Christopher Holloway ◽  
Pier-Luigi Vidale
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Power Input ◽  
Causal Theory ◽  
Density Field ◽  
Secondary Circulation ◽  
Reference State ◽  
Available Potential Energy ◽  
Available Energy ◽  
Surface Enthalpy

<p>While it is well accepted that tropical cyclones (TCs) derive their energy from surface enthalpy fluxes over the ocean, there is still little understanding of the precise causes and effects by which the latter ends up as TC vortex kinetic energy. For example, Potential Intensity (PI) theory, which has been so far the main framework for predicting TC intensities, assumes a balance between the Carnot power input and the kinetic energy dissipated by surface friction, but says nothing of the detailed physical processes linking the two. A similar criticism pertains to the WISHE (Wind Induced Surface Heat Exchange) theory. To achieve a causal theory of TC intensification, the main difficulty is in linking the power input to kinetic energy production, rather than kinetic energy dissipation. Because kinetic energy is produced at the expense of available potential energy (APE), APE theory is arguably the most promising candidate framework for achieving a causal theory of TC intensification. However, in its current form, the usefulness of APE theory appears to be limited in a number of ways because of its reliance on a notional reference state of rest. First, APE production associated with standard reference states (i.e., horizontally averaged density field, density field of initial sounding, adiabatically sorted states, ...) is usually found to systematically overestimate the kinetic energy actually produced in ideal TC simulations, similarly as the Carnot theory of heat engines; moreover, the standard APE is only connected to vertical buoyancy forces, but says nothing of the radial forces required to drive the secondary circulation. To address these shortcomings, this work presents a new theory of available energy (AE) that is based on the use of an axisymmetric vortex reference state in gradient wind balance. This theory possesses the following advantages over previous frameworks:</p><p> </p><ul><li>The available energy (AE) thus constructed possesses both a mechanical and thermodynamic component. The thermodynamic component is analogous to the well-known Slantwise Convective Available Potential Energy (SCAPE), whereas the mechanical component is proportional to the anomalous azimuthal kinetic energy;</li> <li>The rate of AE production by surface enthalpy fluxes is found to be a very accurate predictor of the amount of potential energy actually converted into kinetic energy in idealised TC simulations based on the Rotunno and Emanuel (1986) axisymmetric model, although a few exceptions are found for cold SSTs;</li> <li>In addition to the expected thermodynamic efficiencies, the production term for AE also involves mechanical efficiencies predicting the fraction of the sinks/sources of angular momentum creating/destroying AE;</li> <li>The AE is related to a generalised buoyancy/inertial force that has both vertical and horizontal components; at low levels, such a generalised force has radially inward and vertically upward components, as required to drive the expected secondary circulation.</li> </ul><p>The new theory, therefore, appears to possess all the ingredients to form the basis for a causal theory of TC intensification.</p>

scholarly journals Energy of Midlatitude Transient Eddies in Idealized Simulations of Changed Climates

2008 ◽  
Vol 21 (22) ◽  
pp. 5797-5806 ◽  
Author(s):  
Paul A. O’Gorman ◽  
Tapio Schneider
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Radiative Forcing ◽  
General Circulation ◽  
Thermal Structure ◽  
Circulation Model ◽  
Static Stability ◽  
Eddy Kinetic Energy ◽  
Available Potential Energy ◽  
Wide Range

Abstract As the climate changes, changes in static stability, meridional temperature gradients, and availability of moisture for latent heat release may exert competing effects on the energy of midlatitude transient eddies. This paper examines how the eddy kinetic energy in midlatitude baroclinic zones responds to changes in radiative forcing in simulations with an idealized moist general circulation model. In a series of simulations in which the optical thickness of the longwave absorber is varied over a wide range, the eddy kinetic energy has a maximum for a climate with mean temperature similar to that of present-day earth, with significantly smaller values both for warmer and for colder climates. In a series of simulations in which the meridional insolation gradient is varied, the eddy kinetic energy increases monotonically with insolation gradient. In both series of simulations, the eddy kinetic energy scales approximately linearly with the dry mean available potential energy averaged over the baroclinic zones. Changes in eddy kinetic energy can therefore be related to the changes in the atmospheric thermal structure that affect the mean available potential energy.

scholarly journals Dr. Yanai’s Contributions to the Discovery and Science of the MJO

2016 ◽  
Vol 56 ◽  
pp. 4.1-4.18 ◽  
Author(s):  
Eric D. Maloney ◽  
Chidong Zhang
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Budget ◽  
Momentum Transport ◽  
Energy Budgets ◽  
Equatorial Waves ◽  
Madden Julian Oscillation ◽  
Moist Static Energy ◽  
Moist Static Energy Budget ◽  
Static Energy

Abstract This chapter reviews Professor Michio Yanai’s contributions to the discovery and science of the Madden–Julian oscillation (MJO). Professor Yanai’s work on equatorial waves played an inspirational role in the MJO discovery by Roland Madden and Paul Julian. Professor Yanai also made direct and important contributions to MJO research. These research contributions include work on the vertically integrated moist static energy budget, cumulus momentum transport, eddy available potential energy and eddy kinetic energy budgets, and tropical–extratropical interactions. Finally, Professor Yanai left a legacy through his students, who continue to push the bounds of MJO research.

On the Decadal Variability of the Eddy Kinetic Energy in the Kuroshio Extension

2017 ◽  
Vol 47 (5) ◽  
pp. 1169-1187 ◽  
Author(s):  
Yang Yang ◽  
X. San Liang ◽  
Bo Qiu ◽  
Shuiming Chen
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Decadal Variability ◽  
Kuroshio Extension ◽  
Baroclinic Instability ◽  
Eddy Kinetic Energy ◽  
Time Varying ◽  
Barotropic Instability ◽  
Available Potential Energy ◽  
Decadal Modulation

AbstractPrevious studies have found that the decadal variability of eddy kinetic energy (EKE) in the upstream Kuroshio Extension is negatively correlated with the jet strength, which seems counterintuitive at first glance because linear stability analysis usually suggests that a stronger jet would favor baroclinic instability and thus lead to stronger eddy activities. Using a time-varying energetics diagnostic methodology, namely, the localized multiscale energy and vorticity analysis (MS-EVA), and the MS-EVA-based nonlinear instability theory, this study investigates the physical mechanism responsible for such variations with the state estimate from the Estimating the Circulation and Climate of the Ocean (ECCO), Phase II. For the first time, it is found that the decadal modulation of EKE is mainly controlled by the barotropic instability of the background flow. During the high-EKE state, violent meanderings efficiently induce strong barotropic energy transfer from mean kinetic energy (MKE) to EKE despite the rather weak jet strength. The reverse is true in the low-EKE state. Although the enhanced meander in the high-EKE state also transfers a significant portion of energy from mean available potential energy (MAPE) to eddy available potential energy (EAPE) through baroclinic instability, the EAPE is not efficiently converted to EKE as the two processes are not well correlated at low frequencies revealed in the time-varying energetics. The decadal modulation of barotropic instability is found to be in pace with the North Pacific Gyre Oscillation but with a time lag of approximately 2 years.

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