Dissipation of acoustic-gravity waves: An asymptotic approach

Godin, Oleg A.

doi:10.1121/1.4902426

Cited by 20 publications

(23 citation statements)

References 17 publications

(30 reference statements)

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“…Acoustic‐gravity waves (AGWs) in the atmosphere have the dispersion relation [ Godin , , ]

m^{2} = \frac{ω_{d}^{2}}{c_{s}^{2}} - \frac{γ^{2} g^{2}}{4 c_{s}^{4}} - k^{2} ([], 1 - \frac{((), γ - 1) g^{2}}{ω_{d}^{2} c_{s}^{2}}),

where c s and u are the sound speed and wind velocity, γ ≈ 1.4 is the ratio of specific heats in air at constant pressure and constant volume, ( k x , k y , m ) and ω are the AGW wave vector and frequency, k = ( k x , k y , 0) is the horizontal wave vector, and ω d = ω − k · u is the intrinsic frequency. Here we disregard the effect of dissipative processes on the AGW dispersion relation.…”

Section: Properties Of Atmospheric Wavesmentioning

confidence: 99%

Resonance vibrations of the Ross Ice Shelf and observations of persistent atmospheric waves

Godin

Zabotin

2016

JGR Space Physics

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Recently reported lidar observations have revealed a persistent wave activity in the Antarctic middle and upper atmosphere that has no counterpart in observations at midlatitude and low‐latitude locations. The unusual wave activity suggests a geographically specific source of atmospheric waves with periods of 3–10 h. Here we investigate theoretically the hypothesis that the unusual atmospheric wave activity in Antarctica is generated by the fundamental and low‐order modes of vibrations of the Ross Ice Shelf (RIS). Simple models are developed to describe basic physical properties of resonant vibrations of large ice shelves and their coupling to the atmosphere. Dispersion relation of the long surface waves, which propagate in the floating ice sheet and are responsible for its low‐order resonances, is found to be similar to the dispersion relation of infragravity waves in the ice‐free ocean. The phase speed of the surface waves and the resonant frequencies determine the periods and wave vectors of atmospheric waves that are generated by the RIS resonant oscillations. The altitude‐dependent vertical wavelengths and the periods of the acoustic‐gravity waves in the atmosphere are shown to be sensitive to the physical parameters of the RIS, which can be difficult to measure by other means. Predicted properties of the atmospheric waves prove to be in a remarkable agreement with the key features of the observed persistent wave activity.

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“…Acoustic‐gravity waves (AGWs) in the atmosphere have the dispersion relation [ Godin , , ]

m^{2} = \frac{ω_{d}^{2}}{c_{s}^{2}} - \frac{γ^{2} g^{2}}{4 c_{s}^{4}} - k^{2} ([], 1 - \frac{((), γ - 1) g^{2}}{ω_{d}^{2} c_{s}^{2}}),

Section: Properties Of Atmospheric Wavesmentioning

confidence: 99%

Resonance vibrations of the Ross Ice Shelf and observations of persistent atmospheric waves

Godin

Zabotin

2016

JGR Space Physics

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“…, c 0 is the sound speed, H is the scale height, g is the gravitational acceleration, ω 0 = ω À k Á u = ω À k x u x À k y u y , and u x and u y are the zonal and meridional components of the background neutral wind [Godin, 2015]. In practice, thermospheric AGWs can have a considerable imaginary component of k z , both because there are large spatial regions where they may exist as evanescent waves and because of the viscous attenuation [Godin, 2014]. If a wave is in the shadow zone (this happens when the expression under radical sign in equation (10) is negative), it is still observable, but equation (9) is not valid: vertical gradient of the phase determines a different physical quantity.…”

Section: 1002/2016ja022495mentioning

confidence: 99%

Characteristics of acoustic gravity waves obtained from Dynasonde data

et al. 2016

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Traveling ionospheric disturbances (TIDs) are ubiquitous in the thermosphere‐ionosphere and are often assumed to be caused by acoustic gravity waves (AGWs). This study performs an analysis of the TID and AGW activity above Wallops Island, VA, during October 2013. The variations in electron density and ionospheric tilts obtained with the Dynasonde technique are used as primary indicators of wave activity. The temporal and spectral characteristics of the data are discussed in detail, using also results of the Whole Atmosphere Model (WAM) and the Global Ionosphere Plasmasphere Model (GIP). The full set of propagation parameters (frequency, and the vertical, zonal and meridional wave vector components) of the TIDs is determined over the 160–220 km height range. A test of the self‐consistency of these results within the confines of the theoretical AGW dispersion relation is devised. This is applied to a sample data set of 24 October 2013. A remarkable agreement has been achieved for wave periods between 52 and 21 min, for which we can rigorously claim the TIDs are caused by underlying acoustic gravity waves. The Wallops Island Dynasonde can operate for extended periods at a 2 min cadence, allowing determination of the statistical distributions of propagation parameters. A dominant population of TIDs is identified in the frequency band below 1 mHz, and for it, the distributions of the horizontal wavelengths, vertical wavelengths, and horizontal phase speeds are obtained.

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“…AGWs of oceanic origin, and especially the AGWs radiated by IGWs in deep water, are characterized by considerably higher horizontal phase speeds, which can exceed the maximum wind speeds. This leads to larger horizontal spatial scales and, correspondingly, to weaker viscous absorption (Godin 2014). Fast AGWs do not have critical levels and escape the critical level filtering (Hines 1960;Gossard and Hooke 1975).…”

Section: Observationsmentioning

confidence: 99%

Acoustic-gravity waves in the atmosphere generated by infragravity waves in the ocean

Godin

Zabotin

Bullett

2015

Earth Planets Space

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Infragravity waves are surface gravity waves in the ocean with periods longer than approximately 30 s. Infragravity waves propagate transoceanic distances and, because of their long wavelengths, provide a mechanism for coupling wave processes in the ocean, atmosphere, and the solid Earth. Here, we present a strict physical justification for the hypothesis that background ocean waves may generate waves in the upper atmosphere. We show that, at frequencies below a certain transition frequency of about 3 mHz, infragravity waves continuously radiate their energy into the upper atmosphere in the form of acoustic-gravity waves. Based on ionospheric observations and estimates of the fluxes of the mechanical energy and momentum from the deep ocean, we conclude that acoustic-gravity waves of oceanic origin may have an observable impact on the upper atmosphere. We anticipate our work to be a starting point for a detailed analysis of global manifestations of the ocean-generated background acoustic-gravity waves.

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Dissipation of acoustic-gravity waves: An asymptotic approach

Cited by 20 publications

References 17 publications

Resonance vibrations of the Ross Ice Shelf and observations of persistent atmospheric waves

Resonance vibrations of the Ross Ice Shelf and observations of persistent atmospheric waves

Characteristics of acoustic gravity waves obtained from Dynasonde data

Acoustic-gravity waves in the atmosphere generated by infragravity waves in the ocean

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