Download or read book Nonlinear Internal Gravity Wave Propagation Saturation and Absorption in the Atmosphere written by Timothy J. Dunkerton and published by . This book was released on 1986 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Propagation and Saturation of Nonlinear Inertia Gravity Waves in the Atmosphere written by Timothy J. Dunkerton and published by . This book was released on 1989 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Inertia gravity waves play a significant role in the transport of momentum, heat, and constituents in the terrestrial atmosphere. This transport process is subgrid scale in general circulation models and must be parameterized. A generalized parameterization scheme is developed in which a gravity wave is subject to localized breaking that creates turbulent mixing and retards amplitude growth. The effect of turbulence localization on turbulent viscosity, diffusivity and mean flow acceleration is described for the convectively unstable case. Possible generalizations to Kelvin-Helmholtz breaking are suggested. Numerical simulations at high resolution illustrate the evolution to small scales characteristic of convective instability. (JHD).
Download or read book AFOSR Chemical Atmospheric Sciences Program Review written by United States. Air Force. Directorate of Chemical and Atmospheric Sciences and published by . This book was released on with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effect of Weak Non linearity on Vertically Propagating Internal Gravity Waves in the Atmosphere written by Mostafa M. Ibrahim and published by . This book was released on 1982 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The linear and weakly non-linear limits of two-dimensional gravity waves in an incompressible, inviscid and stably stratified atmosphere are studied. The linear results indicate the growth of waves propagating upward leading to the breakdown of the linear theory. The three-wave resonant interaction theory indicates an energy cascade from a vertically propagating wave (primary wave) to waves having smaller absolute values of Doppler shifted frequency ((OMEGA)). When the non-dimensional parameter" --
Download or read book Gravity Waves in the Atmosphere Instability Saturation and Transport written by and published by . This book was released on 1995 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: The excitation, propagation, breakdown, absorption of gravity waves in the atmosphere is fundamentally important to the momentum balance, transport of heat and constituents, and general circulation. This report describes the results of several studies pertaining to excitation of inertia gravity waves in midlatitude baroclinic systems, effects of the quasi-biennial oscillation on the inertia gravity and Kelvin wave spectrum a the equator, the role of gravity wave drag in the extratropical QBO, destabilization of large-scale tropical waves by deep moist convection, and a general theory of equatorial inertial instability on a zonally nonuniform, nonparallel flow.
Download or read book Propagation and Breaking of Nonlinear Internal Gravity Waves written by Hayley V. Dosser and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Internal Gravity Waves written by Bruce R. Sutherland and published by Cambridge University Press. This book was released on 2010-09-02 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Nonlinear Behavior in the Propagation of Atmospheric Gravity Waves written by Patricia Minthorn Franke and published by . This book was released on 1996 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: Motivated by the need to understand the experimental data from remote sensing systems measuring upper atmospheric parameters, a tool was developed that would allow the simulation of the nonlinear aspects of the propagation of the waves thought to drive the global circulation of the mesosphere-gravity waves. The results from two numerical experiments are presented comparing the dynamics of gravity wave breaking in two different frequency regimes. Analyses of these data are used to test several of the assumptions and implications of the current theories describing the dynamics of this region. The goal of this study is to delve into understanding the nonlinear aspects of the gravity wave forcing of the upper atmosphere and how these nonlinearities appear in the frequency domain. To aid in the interpretation of the results from the fully nonlinear model, three other models, each containing a different subset of the full set of nonlinear terms, were developed: (i) a linear model containing no nonlinear terms, (ii) a quasilinear model containing the nonlinear terms associated with the wave-mean flow interactions only, and (iii) a fixed mean flow model containing the nonlinear terms associated with wave-wave interactions only. Plotting the potential temperature and velocity fields in different ways shows the evolution of the system in each frequency regime, as well as the strong effect of the wave-mean flow interactions on wave breaking. The higher frequency regime exhibits a wave field that breaks the effects of which are confined to a very narrow region. Just enough energy is shed to maintain static stability in the system. Similarly, the low frequency also wave breaks, again just maintaining static stability, but now, the influence of the breaking is felt throughout the grid. In this frequency regime the new components generated by the nonlinearities are propagating. Comparisons of the fully nonlinear model results with those from the fixed mean flow model show that when the wave-mean flow interactions are included in the simulation the gravity wave is allowed to break vigorously; when they are excluded the wave field sheds energy but not through wave breaking (unless the forcing is very strong). The breaking events are also described in the frequency domain. Various spectra are presented illustrating how the nonlinearities move energy from the main forced component into other components. Comparisons between the different models show the relative importance of each set of nonlinear terms in driving different aspects of the energy rearrangement in the spectrum. The wave-wave interactions create higher-order harmonics, some of which may or may not be propagating. The wave-mean flow interactions smear the energy in frequency and vertical wavenumber. Parameterization of the nonlinear terms is the subject of the final section describing the results. Looking at the use of linear saturation theory and diffusion theory to predict the effect of the nonlinearities on wave amplitude and mean-flow creation, this section investigates the basic assumptions behind some of the more popular theories of gravity wave propagation in the mesosphere. The data show that the parameterizations are not generally valid, except under special circumstances. These circumstances are identified and compared with the appropriate theoretical descriptions looking for consistency with the basic assumptions of each theory. These results contain implications for how the different nonlinear processes work to shape the signatures seen in experimental data.
Download or read book Government Reports Annual Index Keyword A L written by and published by . This book was released on 1986 with total page 868 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1978 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book On the Propagation of Atmospheric Gravity Waves in a Non uniform Wind Field written by Ahmad Talaei and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Theoretical and Observational Studies of Gravity Wave Excitation Propagation and Dissipation written by David C. Fritts and published by . This book was released on 1986 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research under this grant focussed on several aspects of gravity wave excitation, propagation, and dissipation that are expected to be important in the atmosphere. Initial studies addressed the excitation of propagating waves by unstable shear layers and found that the nonlinear interaction of evanescent unstable modes is an efficient source of such motion. Other mumerical studies examined the consequences of gravity wave propagation and saturation in the middle atmosphere. Important findings include an amplitude limit imposed by wave field instabilities, the self-accelerations of large-amplitude motions which may greatly expand the phase speed distribution of mesospheric wave motions, and the field instability. Observational studies revealed wave field dynamics to be largely consistent with linear instability theory, with turbulence produces at that site in the wave field where the motion is most unstable. Wave amplitudes were seen to be near saturation value and easily descrived by a simple saturation model of the evolving gravity wave spectrum throughout the atmosphere. Additional theoretical studies addressed the turbulent transport of hear and constituents and the induced mean vertical motions to vertically propagating gravity waves, contributing to our understanding of apparent differences between observations and modeling results.
Download or read book Internal Gravity Waves Observed in Mesospheric Temperature Measurements written by S. P. Zimmerman and published by . This book was released on 1970 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Temperature height profiles determined from falling sphere and Arcasonde measurements, made at White Sands, New Mexico from 23 to 25 January 1967, exhibit unusually large variability in the vicinity of the mesopause. Spatial and temporal analysis of the data exhibit a wave-like structure with vertical half wavelengths of the order of 3 and 30 km and a characteristic period of approximately 12 hours for the longer wavelength. Comparison with meteorological data below 60 km and application of appropriate theory leads to the tentative suggestion that the observed temperature variations were due to internal gravity waves. The analysis also infers that the source of these waves was a large scale, low altitude (approximately 200 mb) synoptic disturbance. This work has been performed in support of re-entry studies for Air Force space vehicles and investigations for improving DOD missile impact prediction capability. (Author).
Download or read book Gravity Wave Generation and Momentum Deposition in the Atmosphere written by Mahtab Majdzadeh and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first part of this study investigates gravity wave parameterization in the middle atmosphere, focusing on internal waves with a broad spectrum of phase speeds. A column model based on CIRA wind and temperature profiles is employed to assess the characteristics of the Hines Doppler-Spread (1997) and Warner-McIntyre-Scinocca (2001) nonorographic drag parameterizations for internal gravity waves. The Alexander-Dunkerton (1999) variant of Warner-McIntyre-Scinocca scheme is also briefly considered. This study goes into more detail than previous comparisons by performing a spectral analysis of the momentum deposition and drag, and by examining the ability of each scheme to reproduce saturation. Comparisons with pure critical level filtering are also made, and it is found that Hines DSP mainly constitutes an enhancement to critical level absorption, while the Warner-McIntyre-Scinocca scheme produces substantially different wave drag profiles. We find several undesirable characteristics in the drag produced by the Hines scheme. For typical midlatitude profiles, it produces an abrupt onset of large accelerations that are confined to a relatively narrow layer. It is also unable to reproduce wave spectra consistent with observed saturation at high vertical wavenumbers. The second part of this study investigates the generation mechanisms of the gravity waves over Newfoundland and Labrador (NL). We performed a series of simulations for a selection of the strongest peak events using WRF model to further investigate the characteristics and generation mechanisms of gravity wave peak events over NL. We studied three different peak events, 2003, 2008 and 2014. We showed that gravity wave events in the winter hotspot region over NL can have both topographic and jet streak sources. In the cases we examined, one source of waves was the Torngat range on the northern coast of Labrador. However, the other two wave sources were in fact outside the hotspot region, and a combination of advection and propagation caused those packets to enter the hotspot in the middle atmosphere. We have demonstrated that topographic wave packets, which are normally assumed to remain stationary over the source, can in fact be advected far downstream from the source.
Download or read book Gravity Wave Processes written by Kevin Hamilton and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of this volume is the observation and modelling of the gravity wave field in the atmosphere. The focus is on the question of how to include the effects of small-scale gravity waves in sophisticated global climate models. The book comprises 26 chapters, including contributions from distinguished experts in observation and theory, along with results from studies of gravity wave parameterization within comprehensive climate models.
Download or read book The Vertical Propagation of Internal Gravity Waves in a Compressible Atmosphere written by Lawrence Coy and published by . This book was released on 1985 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt:
