PROPAGATION OF ACOUSTIC-GRAVITY WAVES IN A TEMPERATURE-AND WIND-STRATIFIED ATMOSPHERE. PDF Download
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Author:
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ISBN:
Category :
Languages : en
Pages : 46
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Book Description
A theory is presented which permits the study of the effects of horizontal winds on the dispersion and amplitudes of acoustic-gravity waves in the atmosphere. It is shown that the effective horizontal group velocity for a given frequency in a given normal mode depends on direction of propagation as well as on frequency and that it is not necessarily in the same direction as the horizontal wave number vector. A number of useful integral theorems are derived from a variational principle and one is subsequently applied to the development of a perturbation method for the computation of wind effects on dispersion. Application of the method to a realistic example indicates that winds can appreciably alter the dispersion of the normal modes and that they should be considered in any quantitative interpretation of experimental microbarograms.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 46
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Book Description
A theory is presented which permits the study of the effects of horizontal winds on the dispersion and amplitudes of acoustic-gravity waves in the atmosphere. It is shown that the effective horizontal group velocity for a given frequency in a given normal mode depends on direction of propagation as well as on frequency and that it is not necessarily in the same direction as the horizontal wave number vector. A number of useful integral theorems are derived from a variational principle and one is subsequently applied to the development of a perturbation method for the computation of wind effects on dispersion. Application of the method to a realistic example indicates that winds can appreciably alter the dispersion of the normal modes and that they should be considered in any quantitative interpretation of experimental microbarograms.
Author: Nayar K. Balachandran
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: United States. Environmental Science Services Administration
Publisher:
ISBN:
Category : Gravity waves
Languages : en
Pages : 462
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Author:
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ISBN:
Category :
Languages : en
Pages : 11
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Book Description
A stably stratified atmosphere supports propagation of internal gravity waves (IGW). These waves result in highly anisotropic fluctuations in temperature and wind velocity that are stretched in a horizontal direction. As a result, (IGW) can significantly affect propagation of sound waves in nighttime boundary layers and infrasound waves in the stratosphere. In this paper, a theory of sound propagation through, and scattering by, (IGW) is developed. First, 3D spectra of temperature and wind velocity fluctuations due to (IGW), which were recently derived in the literature for the case of large wave numbers, are generalized to account for small wave numbers. The generalized 3D spectra are then used to calculate the sound scattering cross section in an atmosphere with (IGW). The dependencies of the obtained scattering cross section on the sound frequency, scattering angle, and other parameters of the problem are qualitatively different from those for the case of sound scattering by isotropic turbulence with the von K rm n spectra of temperature and wind velocity fluctuations. Furthermore, the generalized 3D spectra are used to calculate the mean sound field and the transverse coherence function of a plane sound wave propagating through (IGW). The results obtained also significantly differ from those for the case of sound propagation through isotropic turbulence.
Author: Igor Chunchuzov
Publisher: Cambridge Scholars Publishing
ISBN: 1527547760
Category : Science
Languages : en
Pages : 355
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Book Description
This book presents the theory and results of experimental studies of the propagation of infrasound waves in a real atmosphere with its inherent fine-scale layered structure of wind speed and temperature. It is motivated by the fact that the statistical characteristics of anisotropic (or layered) fluctuations of meteorological fields, the horizontal scales of which significantly exceed their vertical scales, have been very poorly studied compared to those of locally isotropic turbulence in the inertial range of scales. This book addresses this lacuna by developing a theory of the formation of anisotropic inhomogeneities of the atmosphere in a random field of internal gravity waves and vortex structures. Using theory, it explains numerous experimental data depicting the influence of the fine structure of the atmosphere on the propagation of infrasound waves from pulsed sources. The text will appeal to specialists in the fields of acoustics and optics of the atmosphere, remote sensing of the atmosphere, the dynamics of internal waves, nonlinear acoustics, and infrasound monitoring of explosions and natural hazards.
Author: Allan D. PIERCE
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
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Book Description
This paper is concerned with the propagation of acoustic waves in temperature-and wind-stratified atmospheres in the geometrical acoustics' approximation. The basic theory of Blokhintzev is shown to hold for propagation in the atmosphere, even when gravitational forces and pressure gradients are included, if wave periods are sufficiently short. The 'ray-tracing' equations are derived from the eikonal approximation using Cauchy's method of characteristics, and the boundary conditions on these equations appropriate to a point source are discussed. Previous approximate methods of integrating the ray-tracing equations with the neglect of cross-winds are discussed, and a formulation due to Lee is corrected. A numerical method is introduced which alloys cross-winds to be taken into account. An extension of this method, to include earth curvature effects, is also included. (Author).
Author:
Publisher:
ISBN:
Category : Meteorology
Languages : en
Pages : 988
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Author: Ahmad Talaei
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Atmospheric gravity waves play fundamental roles in a broad-range of dynamical processes extending throughout the Earth0́9s neutral atmosphere and ionosphere. In this paper, we present a modified form for the acoustic-gravity wave equation and its dispersion relationships for a compressible and non-stationary atmosphere in hydrostatic balance. Importantly, the solutions have been achieved without the use of the well-known Boussinesq approximation which have been used extensively in previous studies. We utilize the complete set of governing equations for a compressible atmosphere with non-uniform airflows to determine an equation for vertical velocity of possible atmospheric waves. This intricate wave equation is simplified by a proper substitution producing a useful new wave-like equation for acoustic-gravity waves. The substitution introduces a term omega (intrinsic frequency) in the amplitude of the wave solution for the vertical velocity of acoustic-gravity waves. This term may play a significant role in directional filtering of atmospheric waves in realistic atmospheres exhibiting strong and highly variable winds. It is also proven that the only difference in the wave equation of compressible fluid when non-uniform wind is added to the equations of motion is the term with second derivative of Ln(omega) with respect to height. These new solutions may be particularly important for improved gravity wave propagation studies in the upper mesosphere and thermosphere/ionosphere regions.
Author: Allan D. Pierce
Publisher:
ISBN:
Category :
Languages : en
Pages : 98
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Book Description
A computer program written in FORTRAN II for the purpose of studying guided infrasonic (acoustic-gravity) waves in the atmosphere is described. The deck listing of the main program and 43 subroutines is included. The program is based on the multilayer approximation which considers the atmosphere as consisting of a large number (up to 100) of layers, each having constant temperature and wind velocity. Such a model atmosphere may be chosen to approximate any continuously stratified model atmosphere. The report includes instructions for the operation of the program and examples of output. (Author).
Author: Colin O. Hines
Publisher: American Geophysical Union
ISBN: 0875900186
Category : Science
Languages : en
Pages : 1013
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Book Description
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 18. I am advised that a preface, though not necessary, would at least be conventional. Since this provides the one opportunity for conventionality that the volume as a whole opens up, it would be churlish of me to decline. A preface normally includes, I am told, an indication of both the reason that underlies the volume's very existence and the individuals to whom the volume is directed. But part of the reason for the volume's existence lies, strange though it may seem, in communicating the reason for the volume's existence. Since prefaces generally go unread, I would be remiss if I attempted that communication here. Instead, I have left the attempt to the Introduction and Key, which I believe has a better chance of being read. Let us be willing to settle, for the moment, on the truly fundamental fact that the volume was prepared because I was prepared to prepare it and a publisher was prepared to publish it. As to the intended readers; they too, must wait for their identification in the Introduction and Key, unless they are willing to settle at this point on an identification as those who might be ready to read what I was prepared to prepare.
