scholarly journals Testing Lagrangian Theories of Internal Wave Spectra. Part I: Varying the Amplitude and Wavenumbers

2009 ◽  
Vol 66 (5) ◽  
pp. 1077-1100 ◽  
Author(s):  
G. P. Klaassen
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Three Dimensional ◽  
Small Scale ◽  
Wave Spectra ◽  
Wave Fields ◽  
Turbulent Eddies ◽  
Stretching Deformation ◽  
Hydrostatic Balance ◽  
Field Approaches

Abstract A growing body of literature has been built on the premise that kinematic advection produced by linear superpositions of sinusoidal Lagrangian gravity waves confined to lower vertical wavenumbers can provide an explanation for quasi-universal Eulerian spectral tails commonly found in the oceans and the atmosphere. Recently, Hines has established criteria delineating the circumstances in which Eulerian and Lagrangian spectra differ. For conditions in which Hines claims Lagrangian linearity and the production of quasi-universal Eulerian m−3 spectra, a kinematic advection model based on ensembles of seven nonstanding Lagrangian waves reveals the presence of gross violations of continuity and adiabaticity as well as severe departures from hydrostatic balance. Similar infractions are found for other seven-wave ensembles having a broad range of amplitudes and wavenumbers typical of saturated wave fields in the middle atmosphere. Furthermore, m−3 spectra are found only as the Lagrangian wave field approaches a singular state. The singularities in the Lagrangian to Eulerian transformation are induced by stretching deformation fields that form during the superposition of sinusoidal waves with nonparallel wave vectors. Such deformation fields are known to be unstable with respect to three-dimensional vortices. The results strongly suggest that saturated middle atmosphere wave fields are frequently accompanied by small-scale turbulent eddies.

scholarly journals Testing Lagrangian Theories of Internal Wave Spectra. Part II: Varying the Number of Waves

2009 ◽  
Vol 66 (5) ◽  
pp. 1101-1125 ◽  
Author(s):  
G. P. Klaassen
Keyword(s):  
Internal Wave ◽  
Gravity Waves ◽  
Middle Atmosphere ◽  
Wave Spectrum ◽  
Doppler Spread ◽  
Wave Spectra ◽  
Single Wave ◽  
Wave Fields ◽  
Large Numbers ◽  
Lagrangian Frame

Abstract It has been proposed by Allen and Joseph, Hines, and Chunchuzov that the kinematic advection produced by superpositions of sinusoidal Lagrangian gravity waves confined to lower vertical wavenumbers m provides an explanation for the quasi-universal m−3 Eulerian spectral tails commonly found at higher m in the oceans and the atmosphere. In support of these theories, Hines has proposed a prototype wave spectrum claimed to meet criteria for Lagrangian linearity and the production of m−3 Eulerian spectra. Although the shape of the Lagrangian spectrum is claimed not to play a major role in this process, Hines has argued that moderately large numbers of waves are required to ensure quasilinear behavior in the Lagrangian frame. The present results demonstrate that, for amplitudes consistent with measurements of saturated waves in the middle atmosphere and for wavenumbers consistent with Hines’ prototype, adiabatic excesses do not diminish with increasing numbers of waves; in contrast, consistency with adiabatic constraints is only achieved in the limit of a single wave, for which the advective nonlinearity u · ∇ vanishes. Moreover, fields with strong singularities yield Eulerian tail slopes as large as −1.6, whereas those with lesser violations of adiabatic constraints yield Eulerian spectral tail slopes that are much steeper (more strongly negative) than −3. The implications for theories based on superpositions of Lagrangian sinusoidal waves, for the Hines quasilinear criteria, and for the Hines Doppler-spread theory and parameterization are addressed. The results are also relevant for experimentalists interested in spectral analysis of internal wave fields.

scholarly journals Dynamics of Orographic Gravity Waves Observed in the Mesosphere over the Auckland Islands during the Deep Propagating Gravity Wave Experiment (DEEPWAVE)

2016 ◽  
Vol 73 (10) ◽  
pp. 3855-3876 ◽  
Author(s):  
Stephen D. Eckermann ◽  
Dave Broutman ◽  
Jun Ma ◽  
James D. Doyle ◽  
Pierre-Dominique Pautet ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Wave Breaking ◽  
Large Amplitude ◽  
Middle Atmosphere ◽  
Three Dimensional ◽  
Surface Flow ◽  
Heating Rates ◽  
Wave Fields ◽  
Wave Experiment

Abstract On 14 July 2014 during the Deep Propagating Gravity Wave Experiment (DEEPWAVE), aircraft remote sensing instruments detected large-amplitude gravity wave oscillations within mesospheric airglow and sodium layers at altitudes z ~ 78–83 km downstream of the Auckland Islands, located ~1000 km south of Christchurch, New Zealand. A high-altitude reanalysis and a three-dimensional Fourier gravity wave model are used to investigate the dynamics of this event. At 0700 UTC when the first observations were made, surface flow across the islands’ terrain generated linear three-dimensional wave fields that propagated rapidly to z ~ 78 km, where intense breaking occurred in a narrow layer beneath a zero-wind region at z ~ 83 km. In the following hours, the altitude of weak winds descended under the influence of a large-amplitude migrating semidiurnal tide, leading to intense breaking of these wave fields in subsequent observations starting at 1000 UTC. The linear Fourier model constrained by upstream reanalysis reproduces the salient aspects of observed wave fields, including horizontal wavelengths, phase orientations, temperature and vertical displacement amplitudes, heights and locations of incipient wave breaking, and momentum fluxes. Wave breaking has huge effects on local circulations, with inferred layer-averaged westward flow accelerations of ~350 m s−1 h−1 and dynamical heating rates of ~8 K h−1, supporting recent speculation of important impacts of orographic gravity waves from subantarctic islands on the mean circulation and climate of the middle atmosphere during austral winter.

Air mass exchange across the polar vortex edge during a simulated major stratospheric warming

1995 ◽  
Vol 13 (7) ◽  
pp. 745-756 ◽  
Author(s):  
G. Günther ◽  
M. Dameris
Keyword(s):  
Cross Sections ◽  
Middle Atmosphere ◽  
Model Simulation ◽  
Mechanistic Model ◽  
Three Dimensional ◽  
Polar Vortex ◽  
Small Scale ◽  
Stratospheric Warming ◽  
Air Masses ◽  
Physical And Chemical

Abstract. The dynamics of the polar vortex in winter and spring play an important role in explaining observed low ozone values. A quantification of physical and chemical processes is necessary to obtain information about natural and anthropogenic causes of fluctuations of ozone. This paper aims to contribute to answering the question of how permeable the polar vortex is. The transport into and out of the vortex ("degree of isolation") remains the subject of considerable debate. Based on the results of a three-dimensional mechanistic model of the middle atmosphere, the possibility of exchange of air masses across the polar vortex edge is investigated. Additionally the horizontal and vertical structure of the polar vortex is examined. The model simulation used for this study is related to the major stratospheric warming observed in February 1989. The model results show fair agreement with observed features of the major warming of 1989. Complex structures of the simulated polar vortex are illustrated by horizontal and vertical cross sections of potential vorticity and inert tracer. A three-dimensional view of the polar vortex enables a description of the vortex as a whole. During the simulation two vortices and an anticyclone, grouped together in a very stable tripolar structure, and a weaker, more amorphous anticyclone are formed. This leads to the generation of small-scale features. The results also indicate that the permeability of the vortex edges is low because the interior of the vortices remain isolated during the simulation.

scholarly journals Generation of gravity waves from thermal tides in the Venus atmosphere

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Norihiko Sugimoto ◽  
Yukiko Fujisawa ◽  
Hiroki Kashimura ◽  
Katsuyuki Noguchi ◽  
Takeshi Kuroda ◽  
...  
Keyword(s):  
Gravity Waves ◽  
General Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Cloud Layer ◽  
Dimensional Structure ◽  
Wave Radiation ◽  
Small Scale ◽  
Thermal Tides ◽  
Venus Atmosphere

AbstractGravity waves play essential roles in the terrestrial atmosphere because they propagate far from source regions and transport momentum and energy globally. Gravity waves are also observed in the Venus atmosphere, but their characteristics have been poorly understood. Here we demonstrate activities of small-scale gravity waves using a high-resolution Venus general circulation model with less than 20 and 0.25 km in the horizontal and vertical grid intervals, respectively. We find spontaneous gravity wave radiation from nearly balanced flows. In the upper cloud layer (~70 km), the thermal tides in the super-rotation are primary sources of small-scale gravity waves in the low-latitudes. Baroclinic/barotropic waves are also essential sources in the mid- and high-latitudes. The small-scale gravity waves affect the three-dimensional structure of the super-rotation and contribute to material mixing through their breaking processes. They propagate vertically and transport momentum globally, which decelerates the super-rotation in the upper cloud layer (~70 km) and accelerates it above ~80 km.

A study of the occurrence of dynamically unstable conditions in the middle atmosphere

1984 ◽  
Vol 62 (10) ◽  
pp. 963-967 ◽  
Author(s):  
Kevin Hamilton
Keyword(s):  
Gravity Waves ◽  
Wave Breaking ◽  
Middle Atmosphere ◽  
Internal Gravity Waves ◽  
Small Scale ◽  
Simple Analysis ◽  
Quantitative Estimates ◽  
Shear Instabilities ◽  
Vertically Propagating ◽  
The Tropics

There has recently been a great deal of interest in the possibility that vertically propagating internal gravity waves may be dissipated by small-scale convective or shear instabilities in the upper stratosphere and mesosphere. In the present study, a very simple analysis of about 3000 rocket soundings of temperature and wind at several stations between 8°N and 59°N was conducted in order to obtain quantitative estimates of the frequency of occurrence of dynamically unstable conditions as a function of height, latitude, and season. It was found that in about one-third of the profiles, the local Richardson number dropped below 0.25 at some level near the stratopause. From the results, it appears that gravity wave "breaking" generally occurs at considerably higher altitudes in the tropics than in midlatitudes. There is also a fairly clear indication of higher wave breaking levels in summer than in winter, at least at high latitudes.

Improved Middle Atmosphere Climate and Forecasts in the ECMWF Model through a Nonorographic Gravity Wave Drag Parameterization

2010 ◽  
Vol 23 (22) ◽  
pp. 5905-5926 ◽  
Author(s):  
Andrew Orr ◽  
Peter Bechtold ◽  
John Scinocca ◽  
Manfred Ern ◽  
Marta Janiskova
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Middle Atmosphere ◽  
Forecast Error ◽  
Wave Structure ◽  
Stationary Wave ◽  
Wave Drag ◽  
Horizontal Distribution ◽  
Small Scale ◽  
Temperature Structure

Abstract In model cycle 35r3 (Cy35r3) of the ECMWF Integrated Forecast System (IFS), the momentum deposition from small-scale nonorographic gravity waves is parameterized by the Scinocca scheme, which uses hydrostatic nonrotational wave dynamics to describe the vertical evolution of a broad, constant, and isotropic spectrum of gravity waves emanating from the troposphere. The Cy35r3 middle atmosphere climate shows the following: (i) an improved representation of the zonal-mean circulation and temperature structure; (ii) a realistic parameterized gravity wave drag; (iii) a reasonable stationary planetary wave structure and stationary wave driving in July and an underestimate of the generation of stationary wave activity in the troposphere and stationary wave driving in January; (iv) an improved representation of the tropical variability of the stratospheric circulation, although the westerly phase of the semiannual oscillation is missing; and (v) a realistic horizontal distribution of momentum flux in the stratosphere. By contrast, the middle atmosphere climate is much too close to radiative equilibrium when the Scinocca scheme is replaced by Rayleigh friction, which was the standard method of parameterizing the effects of nonorographic gravity waves in the IFS prior to Cy35r3. Finally, there is a reduction in Cy35r3 short-range high-resolution forecast error in the upper stratosphere.

Equatorial oscillations in the middle atmosphere generated by small scale gravity waves

1995 ◽  
Vol 22 (22) ◽  
pp. 3027-3030 ◽  
Author(s):  
J. G. Mengel ◽  
H. G. Mayr ◽  
K. L. Chan ◽  
C. O. Hines ◽  
C. A. Reddy ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Small Scale

Transport and Mixing in the Extratropical Tropopause Region in a High-Vertical-Resolution GCM. Part II: Relative Importance of Large-Scale and Small-Scale Dynamics

2010 ◽  
Vol 67 (5) ◽  
pp. 1315-1336 ◽  
Author(s):  
Kazuyuki Miyazaki ◽  
Shingo Watanabe ◽  
Yoshio Kawatani ◽  
Kaoru Sato ◽  
Yoshihiro Tomikawa ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Large Scale ◽  
Three Dimensional ◽  
Small Scale ◽  
Vertical Resolution ◽  
Tropopause Region ◽  
High Vertical Resolution ◽  
Transport And Mixing ◽  
Extratropical Tropopause

Abstract The relative roles of atmospheric motions on various scales, from mesoscale to planetary scale, in transport and mixing in the extratropical tropopause region are investigated using a high-vertical-resolution general circulation model (GCM). The GCM with a vertical resolution of about 300 m explicitly represents the propagation and breaking of gravity waves and the induced transport and mixing. A downward control calculation shows that the Eliassen–Palm (E-P) flux of the gravity waves diverges and induces a mean equatorward flow in the extratropical tropopause region, which differs from the mean poleward flow induced by the convergence of large-scale E-P fluxes. The diffusion coefficients estimated from the eddy potential vorticity flux in tropopause-based coordinates reveal that isentropic motions diffuse air between 20 K below and 10 K above the tropopause from late autumn to early spring, while vertical mixing is strongly suppressed at around 10–15 K above the tropopause throughout the year. The isentropic mixing is mainly caused by planetary- and synoptic-scale motions, while small-scale motions with a horizontal scale of less than a few thousand kilometers largely affect the three-dimensional mixing just above the tropopause. Analysis of the gravity wave energy and atmospheric instability implies that the small-scale dynamics associated with the dissipation and saturation of gravity waves is a significant cause of the three-dimensional mixing just above the tropopause. A rapid increase in the static stability in the tropopause inversion layer is considered to play an important role in controlling the gravity wave activity around the tropopause.

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