Atmospheric Kinetic Energy Spectra from Global High-Resolution Nonhydrostatic Simulations

2014 ◽  
Vol 71 (11) ◽  
pp. 4369-4381 ◽  
Author(s):  
William C. Skamarock ◽  
Sang-Hun Park ◽  
Joseph B. Klemp ◽  
Chris Snyder
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Constant Pressure ◽  
Energy Spectra ◽  
Vertical Resolution ◽  
Stratified Turbulence ◽  
Model Resolution ◽  
Constant Height ◽  
Velocity Variance ◽  
Model Filter

Abstract Kinetic energy (KE) spectra derived from global high-resolution atmospheric simulations from the Model for Prediction Across Scales (MPAS) are presented. The simulations are produced using quasi-uniform global Voronoi horizontal meshes with 3-, 7.5-, and 15-km mean cell spacings. KE spectra from the MPAS simulations compare well with observations and other simulations in the literature and possess the canonical KE spectra structure including a very-well-resolved shallow-sloped mesoscale region in the 3-km simulation. There is a peak in the vertical velocity variance at the model filter scale for all simulations, indicating the underresolved nature of updrafts even with the 3-km mesh. The KE spectra reveal that the MPAS configuration produces an effective model resolution (filter scale) of approximately 6Δx. Comparison with other published model KE spectra highlight model filtering issues, specifically insufficient filtering that can lead to spectral blocking and the production of erroneous shallow-sloped mesoscale tails in the KE spectra. The mesoscale regions in the MPAS KE spectra are produced without use of kinetic energy backscatter, in contrast to other results reported in the literature. No substantive difference is found in KE spectra computed on constant height or constant pressure surfaces. Stratified turbulence is not resolved with the vertical resolution used in this study; hence, the results do not support recent conjecture that stratified turbulence explains the mesoscale portion of the KE spectrum.

scholarly journals Inconsistent Global Kinetic Energy Spectra in Reanalyses and Models

2021 ◽  
Author(s):  
Jih-Wang Aaron Wang ◽  
Prashant D. Sardeshmukh
Keyword(s):  
High Resolution ◽  
Kinetic Energy ◽  
Viscosity Coefficient ◽  
Energy Spectra ◽  
Model Resolution ◽  
Spectral Slope ◽  
Global Models ◽  
Numerical Damping ◽  
Large Ensembles ◽  
Global Atmospheric Circulation

AbstractGlobal upper tropospheric kinetic energy (KE) spectra in several global atmospheric circulation datasets are examined. The datasets considered include the ERA-Interim, JRA-55, and ERA5 reanalyses and two versions of NOAA-GFS analyses at horizontal resolutions ranging from 0.7° to 0.12°. The mesoscale portions of the spectra are found to be highly inconsistent. This is shown to be mainly due to inconsistencies in the scale-dependent numerical damping and in the large contributions to the global mesoscale KE from the KE in convective regions and near orography.The spectra also generally have a steeper mesoscale slope than the -5/3 slope of the observational Nastrom-Gage spectrum pursued at many modeling centers. The sensitivity of the slope in global models to 1) stochastically perturbing diabatic tendencies and 2) decreasing the horizontal hyper-viscosity coefficient is explored in large ensembles of 10-day forecasts made with the NCEP-GFS (0.7° grid) model. Both changes lead to larger mesoscale KE and a flatter spectral slope. The effect is stronger in the modified hyper-viscosity experiment.These results show that (a) despite assimilating vastly more observations than used in the original Nastrom-Gage studies, current high-resolution global analyses still do not converge to a single “true” global mesoscale KE spectrum, and (b) model KE spectra can be made flatter not just by increasing model resolution but also by perturbing model physics and decreasing horizontal diffusion. Such sensitivities and lack of consensus on the spectral slope also raise the possibility that the true global mesoscale spectral slope may not be a precisely -5/3 slope.

scholarly journals Dependence of Model Energy Spectra on Vertical Resolution

2016 ◽  
Vol 144 (4) ◽  
pp. 1407-1421 ◽  
Author(s):  
Michael L. Waite
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Vertical Mixing ◽  
Energy Spectra ◽  
Small Scale ◽  
Rossby Number ◽  
Vertical Resolution ◽  
Wide Range ◽  
Qualitative Shape ◽  
Vertical Grid

Abstract Many high-resolution atmospheric models can reproduce the qualitative shape of the atmospheric kinetic energy spectrum, which has a power-law slope of −3 at large horizontal scales that shallows to approximately −5/3 in the mesoscale. This paper investigates the possible dependence of model energy spectra on the vertical grid resolution. Idealized simulations forced by relaxation to a baroclinically unstable jet are performed for a wide range of vertical grid spacings Δz. Energy spectra are converged for Δz 200 m but are very sensitive to resolution with 500 m ≤ Δz ≤ 2 km. The nature of this sensitivity depends on the vertical mixing scheme. With no vertical mixing or with weak, stability-dependent mixing, the mesoscale spectra are artificially amplified by low resolution: they are shallower and extend to larger scales than in the converged simulations. By contrast, vertical hyperviscosity with fixed grid-scale damping rate has the opposite effect: underresolved spectra are spuriously steepened. High-resolution spectra are converged except for the stability-dependent mixing case, which are damped by excessive mixing due to enhanced shear over a wide range of horizontal scales. It is shown that converged spectra require resolution of all vertical scales associated with the resolved horizontal structures: these include quasigeostrophic scales for large-scale motions with small Rossby number and the buoyancy scale for small-scale motions at large Rossby number. It is speculated that some model energy spectra may be contaminated by low vertical resolution, and it is recommended that vertical-resolution sensitivity tests always be performed.

The Electron Impact Induced Fragmentation of 1-Aryl-5-hydroxy-1,2,3-triazole-4-carboxamides

1990 ◽  
Vol 43 (12) ◽  
pp. 2021 ◽  
Author(s):  
AT Lebedev ◽  
TY Samguina ◽  
T Blumenthal ◽  
MY Kolobov
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Kinetic Energy ◽  
Electron Impact ◽  
High Resolution Mass Spectrometry ◽  
Energy Spectra ◽  
Molecular Ion ◽  
High Resolution Mass ◽  
Ion Kinetic Energy ◽  
Resolution Mass

The pathways of the electron impact induced fragmentation of 1-aryl-5- hydroxy-1,2,3-triazole-4-carboxamides were studied. The compositions of the key ions were confirmed by high-resolution mass spectrometry. The proposed pathways were established from mass analysed ion kinetic energy spectra, and B/E and B2/E linked scans. A variety of structures for the molecular ion of the title compounds is proposed.

scholarly journals Indications of Stratified Turbulence in a Mechanistic GCM

2013 ◽  
Vol 70 (1) ◽  
pp. 231-247 ◽  
Author(s):  
Sebastian Brune ◽  
Erich Becker
Keyword(s):  
Energy Spectrum ◽  
Kinetic Energy ◽  
General Circulation ◽  
Dynamic Instability ◽  
Circulation Model ◽  
Vertical Resolution ◽  
Stratified Turbulence ◽  
Kinetic Energy Spectrum ◽  
Spectral Flux ◽  
Diffusion Scheme

Abstract The horizontal kinetic energy spectrum and its budget are analyzed on the basis of a general circulation model with simplistic parameterizations of radiative and latent heating. A spectral truncation at total wavenumber 330 is combined with a level spacing of either ~200 m or ~1.5 km from the midtroposphere to the lower stratosphere. The subgrid-scale parameterization consists of a Smagorinsky-type anisotropic diffusion scheme that is scaled by a Richardson criterion for dynamic instability and combined with a stress-tensor-based hyperdiffusion that acts only on the very smallest resolved scales. Simulations with both vertical resolutions show a transition from the synoptic −3 to the mesoscale slope in the upper-tropospheric kinetic energy spectrum. Analysis of the spectral budget indicates that the mesoscale slope can be interpreted as stratified turbulence, as has been proposed in recent works of Lindborg and others, only when a high vertical resolution is applied. In this case, the mesoscale kinetic energy around 300–150 hPa is dominated by the nonrotational flow, and the forward horizontal energy cascade is accompanied by an equally strong forward spectral flux due to adiabatic conversion. This adiabatic conversion mainly results from a vertical potential energy flux that originates in the midtroposphere, where the mesoscale adiabatic conversion is negative. For a conventionally coarse vertical resolution, however, the mesoscale slope in the troposphere is dominated by the rotational flow, and the spectral flux due to adiabatic conversion is not comparable to that associated with horizontal advection.

scholarly journals The Horizontal Spectrum of Vertical Velocities near the Tropopause from Global to Gravity Wave Scales

2019 ◽  
Vol 76 (12) ◽  
pp. 3847-3862 ◽  
Author(s):  
Ulrich Schumann
Keyword(s):  
Kinetic Energy ◽  
Gravity Wave ◽  
Energy Exchange ◽  
Energy Spectra ◽  
Stratified Turbulence ◽  
Free Atmosphere ◽  
Aircraft Measurement ◽  
Small Scales ◽  
Field Campaigns ◽  
Measurement Validity

Abstract Vertical motions are fundamental for atmospheric dynamics. Compared to horizontal motions, the horizontal spectrum of vertical velocity w is less well known. Here, w spectra are related to spectra of horizontal motions in the free atmosphere near the tropopause from global to gravity wave scales. At large scales, w is related to vertically averaged horizontal divergent motions by continuity. At small scales, the velocity energy spectra reach anisotropy as in stably stratified turbulence. Combining these limits approximates the w spectrum from global to small scales. The w spectrum is flat at large scales when the divergent spectrum shows a −2 slope, reaches a maximum at mesoscales after transition to −5/3 slopes, and then approaches a fraction of horizontal kinetic energy. The ratio of vertical kinetic energy to potential energy increases quadratically with wavenumber at large scales. It exceeds unity at small scales in stratified turbulence. Global and regional simulations and two recent aircraft measurement field campaigns support these relationships within 30% deviations. Energy exchange between horizontal and vertical motions may contribute to slope changes in the spectra. The model allows for checking measurement validity. Isotropy at large and small scales varies between the datasets. The fraction of divergent energy is 40%–70% in the measurements, with higher values in the stratosphere. Spectra above the tropopause are often steeper over mountains than over oceans, partly with two −5/3 subranges. A total of 80% of w variance near the tropopause occurs at scales between about 0.5 and 80 km.

scholarly journals Out-of-Cloud Convective Turbulence: Estimation Method and Impacts of Model Resolution

2018 ◽  
Vol 57 (1) ◽  
pp. 121-136 ◽  
Author(s):  
Katelyn A. Barber ◽  
Gretchen L. Mullendore ◽  
M. Joan Alexander
Keyword(s):  
High Resolution ◽  
Turbulence Intensity ◽  
Estimation Method ◽  
Vertical Resolution ◽  
Model Resolution ◽  
The North ◽  
Resolution Model ◽  
High Resolution Model ◽  
Model Setup ◽  
Aviation Operations

AbstractConvectively induced turbulence (CIT) poses both a serious threat to aviation operations and a challenge to forecasting applications. CIT generation and propagation processes occur on scales between 10 and 1000 m and therefore are best treated with high-resolution cloud-resolving models. However, high-resolution model simulations are computationally expensive, limiting their operational use. In this study, summertime convection in the North Dakota region is simulated over a 1-week period using a variety of model setups that are similar to those utilized in operational and research applications. Eddy dissipation rate and Ellrod index, both popular turbulence metrics, are evaluated across various model resolutions and compared with pilot reports from aircraft. The Ellrod index was found to be extremely sensitive to model resolution and overestimated turbulence intensity. The variability of turbulence values with respect to model resolution and distance away from convection is also examined. Turbulence probability was found to be the greatest when farther than 20 mi (32.2 km) away from convective cores. Model resolution was found to influence the intensity of predicted turbulence, and the model setup with the highest horizontal and vertical resolution predicted the highest turbulence values. However, the influence on turbulence intensity of vertical resolution and convective properties, such as storm depth, was found to be minimal for 3-km horizontal grid spacing.

Stratified turbulence forced in rotational and divergent modes

2007 ◽  
Vol 586 ◽  
pp. 83-108 ◽  
Author(s):  
E. LINDBORG ◽  
G. BRETHOUWER
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Dynamic Process ◽  
Boussinesq Equations ◽  
Inertial Range ◽  
Energy Spectra ◽  
Stratified Turbulence ◽  
Frequency Spectra ◽  
Forward Energy ◽  
Simulation Results

We perform numerical box simulations of strongly stratified turbulence. The equations solved are the Boussinesq equations with constant Brunt–Väisälä frequency and forcing either in rotational or divergent modes, or, with another terminology, in vortical or wave modes. In both cases, we observe a forward energy cascade and inertial-range scaling of the horizontal kinetic and potential energy spectra. With forcing in rotational modes, there is approximate equipartition of kinetic energy between rotational and divergent modes in the inertial range. With forcing in divergent modes the results are sensitive to the vertical forcing wavenumber kfv. If kfv is sufficiently large the dynamics is very similar to the dynamics of the simulations which are forced in rotational modes, with approximate equipartition of kinetic energy in rotational and divergent modes in the inertial range. Frequency spectra of rotational, divergent and potential energy are calculated for individual Fourier modes. Waves are present at low horizontal wavenumbers corresponding to the largest scales in the boxes. In the inertial range, the frequency spectra exhibit no distinctive peaks in the internal wave frequency. In modes for which the vertical wavenumber is considerably larger than the horizontal wavenumber, the frequency spectra of rotational and divergent modes fall on top of each other. The simulation results indicate that the dynamics of rotational and divergent modes develop on the same time scale in stratified turbulence. We discuss the relevance of our results to atmospheric and oceanic dynamics. In particular, we review a number of observational reports indicating that stratified turbulence may be a prevalent dynamic process in the ocean at horizontal scales of the order of 10 or 100 m up to several kilometres.

Kinetic energy spectra of divergent wind in the atmosphere

Tellus ◽  
1981 ◽  
Vol 33 (1) ◽  
pp. 102-104 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Joseph J. Tribbia
Keyword(s):  
Kinetic Energy ◽  
Energy Spectra ◽  
Divergent Wind

scholarly journals Correlation between Buoyancy Flux, Dissipation and Potential Vorticity in Rotating Stratified Turbulence

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 157
Author(s):  
Duane Rosenberg ◽  
Annick Pouquet ◽  
Raffaele Marino
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Potential Vorticity ◽  
Isotropic Turbulence ◽  
Joint Probability ◽  
Buoyancy Flux ◽  
Turbulent Regime ◽  
Stratified Turbulence ◽  
Low Dissipation ◽  
Linear And Nonlinear

We study in this paper the correlation between the buoyancy flux, the efficiency of energy dissipation and the linear and nonlinear components of potential vorticity, PV, a point-wise invariant of the Boussinesq equations, contrasting the three identified regimes of rotating stratified turbulence, namely wave-dominated, wave–eddy interactions and eddy-dominated. After recalling some of the main novel features of these flows compared to homogeneous isotropic turbulence, we specifically analyze three direct numerical simulations in the absence of forcing and performed on grids of 10243 points, one in each of these physical regimes. We focus in particular on the link between the point-wise buoyancy flux and the amount of kinetic energy dissipation and of linear and nonlinear PV. For flows dominated by waves, we find that the highest joint probability is for minimal kinetic energy dissipation (compared to the buoyancy flux), low dissipation efficiency and low nonlinear PV, whereas for flows dominated by nonlinear eddies, the highest correlation between dissipation and buoyancy flux occurs for weak flux and high localized nonlinear PV. We also show that the nonlinear potential vorticity is strongly correlated with high dissipation efficiency in the turbulent regime, corresponding to intermittent events, as observed in the atmosphere and oceans.

Sign in / Sign up

Export Citation Format

Share Document