Atmospheric Kinetic Energy Spectra from Global High-Resolution Nonhydrostatic Simulations

Skamarock, William C.; Park, Sang Hun; Klemp, Joseph B.; Snyder, Chris

doi:10.1175/jas-d-14-0114.1

Cited by 143 publications

(187 citation statements)

References 39 publications

(68 reference statements)

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“…Models also show a pattern of enhanced mesoscale energies in regions of high topography (Hamilton et al, 2008). The simulations further show that the mesoscale spectrum is not the result of stratified turbulence (Skamarock et al, 2014), in agreement with our conclusion that they are the signature of inertia-gravity waves.…”

Section: Discussionsupporting

confidence: 87%

Submesoscale turbulence in the upper ocean

Callies¹

2016

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Submesoscale flows, current systems 1-100 km in horizontal extent, are increasingly coming into focus as an important component of upper-ocean dynamics. A range of processes have been proposed to energize submesoscale flows, but which process dominates in reality must be determined observationally. We diagnose from observed flow statistics that in the thermocline the dynamics in the submesoscale range transition from geostrophic turbulence at large scales to inertia-gravity waves at small scales, with the transition scale depending dramatically on geographic location. A similar transition is shown to occur in the atmosphere, suggesting intriguing similarities between atmospheric and oceanic dynamics. We furthermore diagnose from upper-ocean observations a seasonal cycle in submesoscale turbulence: fronts and currents are more energetic in the deep wintertime mixed layer than in the summertime seasonal thermocline. This seasonal cycle hints at the importance of baroclinic mixed layer instabilities in energizing submesoscale turbulence in winter. To better understand this energization, three aspects of the dynamics of baroclinic mixed layer instabilities are investigated. First, we formulate a quasigeostrophic model that describes the linear and nonlinear evolution of these instabilities. The simple model reproduces the observed wintertime distribution of energy across scales and depth, suggesting it captures the essence of how the submesoscale range is energized in winter. Second, we investigate how baroclinic instabilities are affected by convection, which is generated by atmospheric forcing and dominates the mixed layer dynamics at small scales. It is found that baroclinic instabilities are remarkably resilient to the presence of convection and develop even when rapid overturns keep the mixed layer unstratified. Third, we discuss the restratification induced by baroclinic mixed layer instabilities. We show that the rate of restratification depends on characteristics of the baroclinic eddies themselves, a dependence not captured by a previously proposed parameterization. These insights sharpen our understanding of submesoscale dynamics and can help focus future inquiry into whether and how submesoscale flows influence the ocean's role in climate.Thesis supervisor: Raffaele Ferrari Title: Breene M. Kerr Professor of Oceanography

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Section: Discussionsupporting

confidence: 87%

Submesoscale turbulence in the upper ocean

Callies¹

2016

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“…In this context, we note that recent atmospheric simulations show that the crossing between the wave and vortex modes occur at a smaller scale for the tropospheric (less stable) flow than for the stratospheric (more stable) flow [41], in agreement with our k R ∼ F r −1 result.…”

Section: Discussionsupporting

confidence: 91%

Interplay of waves and eddies in rotating stratified turbulence and the link with kinetic-potential energy partition

Marino¹,

Rosenberg²,

Herbert³

et al. 2015

EPL

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The interplay between waves and eddies in stably stratified rotating flows is investigated by means of world-class direct numerical simulations using up to 3072 3 grid points. Strikingly, we find that the shift from vortex to wave dominated dynamics occurs at a wavenumber kR which does not depend on Reynolds number, suggesting that partition of energy between wave and vortical modes is not sensitive to the development of turbulence at the smaller scales. We also show that kR is comparable to the wavenumber at which exchanges between kinetic and potential modes stabilize at close to equipartition, emphasizing the role of potential energy, as conjectured in the atmosphere and the oceans. Moreover, kR varies as the inverse of the Froude number as explained by the scaling prediction proposed, consistent with recent observations and modeling of the Mesosphere-Lower Thermosphere and of the ocean.

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“…Another avenue for progress in understanding the mesoscale dynamics is to build on work with numerical models that resolve the mesoscale range (e.g., Hamilton et al 2008;Skamarock et al 2014;Bierdel et al 2016). These models have been shown to compare favorably against observations and could be used to more extensively explore the dynamics of mesoscale flows.…”

Section: Discussionmentioning

confidence: 99%

The Dynamics of Mesoscale Winds in the Upper Troposphere and Lower Stratosphere

Callies

Bühler

Ferrari

2016

Journal of the Atmospheric Sciences

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Spectral analysis is applied to infer the dynamics of mesoscale winds from aircraft observations in the upper troposphere and lower stratosphere. Two datasets are analyzed: one collected aboard commercial aircraft and one collected using a dedicated research aircraft. A recently developed wave-vortex decomposition is used to test the observations' consistency with linear inertia-gravity wave dynamics. The decomposition method is shown to be robust in the vicinity of the tropopause if flight tracks vary sufficiently in altitude. For the lower stratosphere, the decompositions of both datasets confirm a recent result that mesoscale winds are consistent with the polarization and dispersion relations of inertia-gravity waves. For the upper troposphere, however, the two datasets disagree: only the research aircraft data indicate consistency with linear wave dynamics at mesoscales. The source of the inconsistency is a difference in mesoscale variance of the measured along-track wind component. To further test the observed flow's consistency with linear wave dynamics, the ratio between tropospheric and stratospheric mesoscale energy levels is compared to a simple model of upward-propagating waves that are partially reflected at the tropopause. For both datasets, the observed energy ratio is roughly consistent with the simple wave model, but wave frequencies diagnosed from the data draw into question the applicability of the monochromatic theory at wavelengths smaller than 10 km.

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Atmospheric Kinetic Energy Spectra from Global High-Resolution Nonhydrostatic Simulations

Cited by 143 publications

References 39 publications

Submesoscale turbulence in the upper ocean

Submesoscale turbulence in the upper ocean

Interplay of waves and eddies in rotating stratified turbulence and the link with kinetic-potential energy partition

The Dynamics of Mesoscale Winds in the Upper Troposphere and Lower Stratosphere

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