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

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 Ocean Convective Available Potential Energy. Part II: Energetics of Thermobaric Convection and Thermobaric Cabbeling

2016 ◽  
Vol 46 (4) ◽  
pp. 1097-1115 ◽  
Author(s):  
Zhan Su ◽  
Andrew P. Ingersoll ◽  
Andrew L. Stewart ◽  
Andrew F. Thompson
Keyword(s):  
Potential Energy ◽  
Deep Convection ◽  
Center Of Mass ◽  
Convective Available Potential Energy ◽  
Vertical Mixing ◽  
Available Potential Energy ◽  
Energy Part ◽  
Different Temperatures ◽  
Simplifying Assumptions ◽  
Diabatic Processes

AbstractThe energetics of thermobaricity- and cabbeling-powered deep convection occurring in oceans with cold freshwater overlying warm salty water are investigated here. These quasi-two-layer profiles are widely observed in wintertime polar oceans. The key diagnostic is the ocean convective available potential energy (OCAPE), a concept introduced in a companion piece to this paper (Part I). For an isolated ocean column, OCAPE arises from thermobaricity and is the maximum potential energy (PE) that can be converted into kinetic energy (KE) under adiabatic vertical parcel rearrangements. This study explores the KE budget of convection using two-dimensional numerical simulations and analytical estimates. The authors find that OCAPE is a principal source for KE. However, the complete conversion of OCAPE to KE is inhibited by diabatic processes. Further, this study finds that diabatic processes produce three other distinct contributions to the KE budget: (i) a sink of KE due to the reduction of stratification by vertical mixing, which raises water column’s center of mass and thus acts to convert KE to PE; (ii) a source of KE due to cabbeling-induced shrinking of the water column’s volume when water masses with different temperatures are mixed, which lowers the water column’s center of mass and thus acts to convert PE into KE; and (iii) a reduced production of KE due to diabatic energy conversion of the KE convertible part of the PE to the KE inconvertible part of the PE. Under some simplifying assumptions, the authors also propose a theory to estimate the maximum depth of convection from an energetic perspective. This study provides a potential basis for improving the convection parameterization in ocean models.

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.

scholarly journals Submesoscale Dynamics in the Northern Gulf of Mexico. Part II: Temperature–Salinity Relations and Cross-Shelf Transport Processes

2017 ◽  
Vol 47 (9) ◽  
pp. 2347-2360 ◽  
Author(s):  
Roy Barkan ◽  
James C. McWilliams ◽  
M. Jeroen Molemaker ◽  
Jun Choi ◽  
Kaushik Srinivasan ◽  
...  
Keyword(s):  
Potential Energy ◽  
Gulf Of Mexico ◽  
Horizontal Resolution ◽  
Relative Effect ◽  
Distribution Functions ◽  
Transport Processes ◽  
Effect Of Temperature ◽  
Loop Current ◽  
Northern Gulf Of Mexico ◽  
Available Potential Energy

AbstractThis paper, the second of three, investigates submesoscale dynamics in the northern Gulf of Mexico under the influence of the Mississippi–Atchafalaya River system, using numerical simulations at 500-m horizontal resolution with climatological atmospheric forcing. The Turner angle Tu, a measure of the relative effect of temperature and salinity on density, is examined with respect to submesoscale current generation in runs with and without riverine forcing. Surface Tu probability density functions in solutions including rivers show a temperature-dominated signal offshore, associated with Loop Current water, and a nearshore salinity-dominated signal, associated with fresh river water, without a clear compensating signal, as often found instead in the ocean’s mixed layer. The corresponding probability distribution functions in the absence of rivers differ, illustrating the key role played by the freshwater output in determining temperature–salinity distributions in the northern Gulf of Mexico during both winter and summer. A quantity referred to as temperature–salinity covariance is proposed to determine what fraction of the available potential energy that is released during the generation of submesoscale circulations leads to the destruction of density gradients while leaving spice gradients untouched, thereby leading to compensation. It is shown that the fresh river fronts to the east of the Bird’s Foot can evolve toward compensation in concert with a gradual release of available potential energy. It is further demonstrated that, during winter, the cross-shelf freshwater transport mechanism to the west of the Bird’s Foot is well approximated by a diffusive process, whereas to the east is better represented by a ballistic process associated with the Mississippi water that converges in a jetlike pattern.

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