On the Characteristics of Gravity Waves Generated by Atmospheric Shear Layers

Lalas, D. P.; Einaudi, Franco

doi:10.1175/1520-0469(1976)033<1248:otcogw>2.0.co;2

Cited by 85 publications

(37 citation statements)

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“…As a result, sources of atmospheric GWs have received a great deal of attention. Significant tropospheric sources include topography, convective and frontal activities (Bretherton and Smolarkiewicz 1989;Shutts and Gray 1994), wind-shear instabilities (Lalas and Einaudi 1976, Rosenthal and Lindzen 1983, Lott et al 1992, nonmodal growth (Lott 1997, Bakas andIoannou 2007) and geostrophic adjustment.…”

Section: Introductionmentioning

confidence: 99%

Gravity Waves Generated by Sheared Potential Vorticity Anomalies

Lott

Plougonven

Vanneste

2010

Journal of the Atmospheric Sciences

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The gravity waves generated by potential-vorticity anomalies in a rotating stratified shear flow are examined under the assumptions of constant vertical shear, twodimensionality and unbounded domain. Near a potential-vorticity anomaly, the associated perturbation is well modelled by quasi-geostrophic theory. This is not the case at large vertical distances, however, and in particular beyond the two inertial layers that appear above and below the anomaly; there, the perturbation is made of vertically propagating gravity waves. This structure is described analytically, using an expansion in the continuous spectrum of the singular modes that results from the presence of critical levels.Several explicit results are obtained. These include the form of the Eliassen-Palm flux as a function of the Richardson number N 2 /Λ 2 , where N is the Brunt-Väisälä frequency and Λ the vertical shear. Its non-dimensional value is shown to be approximately exp(−πN/Λ)/8 in the far-field, gravity-wave region, and approximately twice that between the two inertial layers. These results, which imply substantial wave-flow interactions in the inertial layers, are valid for Richardson numbers larger than 1, and for a large range of potential-vorticity distributions; In dimensional form they provide simple relationships between the Eliassen-Palm fluxes and the large-scale flow characteristics.As an illustration, we consider a potential-vorticity disturbance with an amplitude of 1 PVU and a depth of 1 km, and estimate that the associated Eliassen-Palm flux ranges between 0.1 mPa and 100 mPa for a Richardson number between 1 and 10. These values of the flux compare with those observed in the lower stratosphere, which suggests that the mechanism identified in this paper provides a substantial gravity-wave source, one that could be parameterized in GCMs.

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Section: Introductionmentioning

confidence: 99%

Gravity Waves Generated by Sheared Potential Vorticity Anomalies

Lott

Plougonven

Vanneste

2010

Journal of the Atmospheric Sciences

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“…Relatively simple background profiles, such as constant shear layer between constant velocity layers (Taylor 1931;Miles and Howard 1964;Lawrence et al 1991) and hyperbolic tangent function (Drazin 1958;Thorpe 1973;Davis and Peltier 1976), have been studied and have provided an understanding of how the properties of shear-unstable modes, such as wavelength, frequency, phase speed, and growth rate, are related to the background flow profiles. Solutions for these simplified profiles have also been used to suggest shear instabilities as the generation mechanism for some waves observed in the atmosphere (e.g., Lalas and Einaudi 1976) and in the ocean (e.g., Woods 1968;Sutherland 1996). However, the onset of instability and the characteristics of the unstable modes are sensitive to details in the background density and velocity profiles (e.g., Howard and Maslowe 1973).…”

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confidence: 99%

Wind‐shear‐generated high‐frequency internal waves as precursors to mixing in a stratified lake

Gímez-Giraldo

Imberger

Antenucci

et al. 2008

Limnology & Oceanography

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Field data were used to estimate the wavelength, phase speed, direction of propagation, frequency, and the vertical structure of high-frequency internal waves observed on the crests of basin-scale waves of Lake Kinneret during periods of strong wind. Shear stability analysis indicates that these waves were generated by shear in the surface mixing layer. The characteristics of the high-frequency internal waves changed within a wind event as the result of the evolution of the background flow conditions following the deepening of the surface layer and the propagation of the basin-scale internal waves. When the background conditions were appropriate, the vertical structure of the unstable mode was such that the perturbations generated visible sinuous internal waves that in turn modified the density profile in the metalimnion in such a way that secondary shear instabilities were triggered. The high-frequency internal waves were observed over larger distances, but poor coherence in temperature records from stations 200 m apart indicated that individual high-frequency internal waves were dissipated locally; these waves are thus a local mechanism allowing energy to be drawn from the energized surface layer and transported to the metalimnion, where it sustains turbulence. Part of the energy extracted from the surface layer was also returned to the mean flow in the metalimnion; high-frequency internal waves are therefore also a source of momentum for the metalimnetic currents. The vertical excursions of the waves also indicate that they could potentially play a role in phytoplankton growth by significantly altering the light regime at relatively high frequencies.

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“…They also may form because of large-scale internal gravity waves, generated by processes including geostrophic adjustment, shear instability, and even leeside cold fronts (Lalas and Einaudi 1976;Uccellini and Koch 1987), perturbing the low-level stable layer. Solitary waves are most often seen as waves of elevation, but they may be characterized by multiple waves of elevation (and depression), with each successive wave becoming weaker (Bosart et al 1998).…”

Section: B Solitary Wavesmentioning

confidence: 99%

Review and case studies of non-traditional severe local windstorms

Coleman¹,

Knupp²

2016

J. Operational Meteor.

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Coleman, T. A., and K. R. Knupp, 2016: Review and case studies of non-traditional severe local windstorms. ABSTRACT Several phenomena not traditionally thought of as severe local storms may produce high winds and subsequent wind damage. These include wake lows, solitary waves, and steep cold fronts. In this paper, the basic dynamics of these phenomena are reviewed, including how they produce strong winds. Impedance relations are shown to provide a good indicator of the potential winds from these pressure perturbation events. A case study of each phenomenon producing significant winds or wind damage is presented, including operational clues that the event is imminent or in progress.

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On the Characteristics of Gravity Waves Generated by Atmospheric Shear Layers

Cited by 85 publications

References 0 publications

Gravity Waves Generated by Sheared Potential Vorticity Anomalies

Gravity Waves Generated by Sheared Potential Vorticity Anomalies

Wind‐shear‐generated high‐frequency internal waves as precursors to mixing in a stratified lake

Review and case studies of non-traditional severe local windstorms

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