On The Propagation Of Atmospheric Gravity Waves In A Non Uniform Wind Field
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| Author | : Ahmad Talaei |
| Publisher | : |
| Total Pages | : |
| Release | : 2016 |
| Genre | : |
| ISBN | : |
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 | : |
| Publisher | : |
| Total Pages | : 35 |
| Release | : 2007 |
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| ISBN | : |
The flow of wind over mountain ranges is believed to be one of the primary generation mechanisms of atmospheric gravity waves. Mountain gravity waves contribute to the production of stratospheric turbulence, a potential cause of accidents in high-altitude aircraft flights. In an effort to advance the current capabilities of forecasting stratospheric turbulence, theoretical models have been developed for the generation and breakdown of mountain gravity waves under realistic conditions, including effects not captured by existing forecasting tools. Specifically, short-scale oscillations in the background buoyancy-frequency profile, often seen in balloon measurements, but normally ignored in theoretical models, are found to cause significantly increased gravity-wave activity, resulting in wave breaking above and upstream of the mountain. The effect of temporal variations in the wind velocity is also studied for a range of amplitudes and periods typical of those encountered in the field. Transient gravity waves resulting from such variations can be significant, and steady flow states predicted on the assumption of uniform wind may not be attainable. Finally, a study is made of the nonlinear evolution of a gravity-wave packet as it propagates upwards in the atmosphere, generating low-frequency inertial-gravity waves of the type seen in recent field observations.
| Author | : Peter Janssen |
| Publisher | : Cambridge University Press |
| Total Pages | : 310 |
| Release | : 2004-10-28 |
| Genre | : Science |
| ISBN | : 0521465400 |
This book was published in 2004. The Interaction of Ocean Waves and Wind describes in detail the two-way interaction between wind and ocean waves and shows how ocean waves affect weather forecasting on timescales of 5 to 90 days. Winds generate ocean waves, but at the same time airflow is modified due to the loss of energy and momentum to the waves; thus, momentum loss from the atmosphere to the ocean depends on the state of the waves. This volume discusses ocean wave evolution according to the energy balance equation. An extensive overview of nonlinear transfer is given, and as a by-product the role of four-wave interactions in the generation of extreme events, such as freak waves, is discussed. Effects on ocean circulation are described. Coupled ocean-wave, atmosphere modelling gives improved weather and wave forecasts. This volume will interest ocean wave modellers, physicists and applied mathematicians, and engineers interested in shipping and coastal protection.
| Author | : Mangalathayil Ali Abdu |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 479 |
| Release | : 2011-02-26 |
| Genre | : Science |
| ISBN | : 9400703260 |
This book is a multi-author treatise on the most outstanding research problems in the field of the aeronomy of the Earth’s atmosphere and ionosphere, encompassing the science covered by Division II of the International Association of Geomagnetism and Aeronomy (IAGA). It contains several review articles and detailed papers by leading scientists in the field. The book is organized in five parts: 1) Mesosphere-Lower Thermosphere Dynamics and Chemistry; 2) Vertical Coupling by Upward Propagating Waves; 3) Ionospheric Electrodynamics and Structuring; 4) Thermosphere- Ionosphere Coupling, Dynamics and Trends and 5) Ionosphere-Thermosphere Disturbances and Modeling. The book consolidates the progress achieved in the field in recent years and it serves as a useful reference for graduate students as well as experienced researchers.
| Author | : Bruce R. Sutherland |
| Publisher | : Cambridge University Press |
| Total Pages | : 395 |
| Release | : 2010-09-02 |
| Genre | : Science |
| ISBN | : 1316184323 |
The study of internal gravity waves provides many challenges: they move along interfaces as well as in fully three-dimensional space, at relatively fast temporal and small spatial scales, making them difficult to observe and resolve in weather and climate models. Solving the equations describing their evolution poses various mathematical challenges associated with singular boundary value problems and large amplitude dynamics. This book provides the first comprehensive treatment of the theory for small and large amplitude internal gravity waves. Over 120 schematics, numerical simulations and laboratory images illustrate the theory and mathematical techniques, and 130 exercises enable the reader to apply their understanding of the theory. This is an invaluable single resource for academic researchers and graduate students studying the motion of waves within the atmosphere and ocean, and also mathematicians, physicists and engineers interested in the properties of propagating, growing and breaking waves.
| Author | : |
| Publisher | : |
| Total Pages | : 1460 |
| Release | : 1991 |
| Genre | : Aeronautics |
| ISBN | : |
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
| Author | : Timothy J. Dunkerton |
| Publisher | : |
| Total Pages | : 23 |
| Release | : 1986 |
| Genre | : |
| ISBN | : |
Numerical and theoretical studies of internal gravity waves have been performed to understand the role of convective instabilities in nonlinear, large amplitude gravity waves; the effects of saturation and self acceleration on transient gravity wave, mean flow interaction; the role of local convective instabilities in producing turbulent modifications of potential temperature and trace constituents in breaking gravity waves; and the propagation and refraction of inertial and non inertial gravity waves through observed middle atmosphere wind fields. Simulations with a two dimensional, nonhydrostatic gravity wave model indicate that convective adjustment in unstable gravity waves results in a mean flow modification closely approximated by WKB saturation theory in cases where the incident wave field is nearly monochromatic. Convection also limits, and practically prevents, the evolution to a reflecting nonlinear critical layer, even when the incident wave field is not monochromatic. Some critical layer dislocation is observed due to self acceleration in transient gravity waves. Localization of turbulence in a convectively unstable gravity wave can greatly reduce the mixing of heat and trace constituents and implies a large turbulent Prandtl number. Significant lateral movement and refraction of gravity wave rays is observed for inertia gravity waves in realistic wintertime flows. A formula is derived for the onset of dynamical instability in inertia-gravity waves, having a lower threshold than the corresponding amplitude required for convective instability.
| Author | : Carmen J. Nappo |
| Publisher | : Elsevier |
| Total Pages | : 300 |
| Release | : 2002-09-12 |
| Genre | : Science |
| ISBN | : 0080491669 |
Gravity waves exist in all types of geophysical fluids, such as lakes, oceans, and atmospheres. They play an important role in redistributing energy at disturbances, such as mountains or seamounts and they are routinely studied in meteorology and oceanography, particularly simulation models, atmospheric weather models, turbulence, air pollution, and climate research. An Introduction to Atmospheric Gravity Waves provides readers with a working background of the fundamental physics and mathematics of gravity waves, and introduces a wide variety of applications and numerous recent advances. Nappo provides a concise volume on gravity waves with a lucid discussion of current observational techniques and instrumentation. Foreword is written by Prof. George Chimonas, a renowned expert on the interactions of gravity waves with turbulence. CD containing real data, computer codes for data analysis and linear gravity wave models included with the text
| Author | : PLUMB |
| Publisher | : Birkhäuser |
| Total Pages | : 465 |
| Release | : 2013-11-21 |
| Genre | : Science |
| ISBN | : 3034858256 |
PAGEOPH, stratosphere, these differences provide us with new evidence, interpretation of which can materially help to advance our understanding of stratospheric dynamics in general. It is now weil established that smaller-scale motions-in particular gravity waves and turbulence-are of fundamental importance in the general circulation of the mesosphere; they seem to be similarly, if less spectacularly, significant in the troposphere, and probably also in the stratosphere. Our understanding of these motions, their effects on the mean circulation and their mutual interactions is progressing rapidly, as is weil illustrated by the papers in this issue; there are reports of observational studies, especially with new instruments such as the Japanese MV radar, reviews of the state of theory, a laboratory study and an analysis of gravity waves and their effects in the high resolution "SKYHI" general circulation model. There are good reasons to suspect that gravity waves may be of crucial significance in making the stratospheric circulation the way it is (modeling experience being one suggestive piece of evidence for this). Direct observational proof has thus far been prevented by the difficulty of making observations of such scales of motion in this region; in one study reported here, falling sphere observations are used to obtain information on the structure and intensity of waves in the upper stratosphere.
| Author | : |
| Publisher | : |
| Total Pages | : 21 |
| Release | : 1997 |
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| ISBN | : |
The "Doppler spread" theory of atmospheric gravity waves has developed rapidly in recent years, from an initial theory of wave spectra into a general parameterization of gravity wave effects for use in global models of the middle atmosphere. Yet the theory currently employs certain key approximations that have still to be tested. The author focuses on the omission of the propagation of the other waves in the spectrum when determining the Doppler spreading of a given gravity wave. This approximation is shown to become untenable as waves are refracted to progressively shorter vertical scales, so ray methods are employed to investigate the refraction characteristics of short waves within propagating long-wave fields. Short-wave refraction is reduced compared to the Doppler-spread results. While turning levels are common, critical levels do not occur if all waves propagate upward in the absence of mean wind shear. Consequently, a sharp increase in the probability of wave obliteration beyond the so-called cutoff vertical wavenumber (a central tenet of Doppler-spread theory) no longer occurs. Possible implications of these results for models of wave-field interactions, spectra, and momentum deposition are discussed.
