Download or read book The Impact of Thermally Forced Nonperiodic Internal Gravity Waves on Convective Development written by Daniel Lee Weekley and published by . This book was released on 2001-09 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thermal forcing in the upper troposphere resulting from deep convection produces internal gravity-wave like disturbances called buoyancy bores. Although they propagate in a manner similar to gravity waves, their structure in time and space is nonperiodic; they travel as a pulse, propagating radially in all directions from the source of thermal forcing. The passage of these bores through the troposphere causes vertical displacements throughout the column in which they occupy. The actual displacements depend upon the vertical structure, or mode, of the bore. Some bores cause local subsidence, while other bores are characterized low-level ascent and upper-level subsidence. Based upon idealized simulations, theories about the contribution of bores to the suppression or enhancement of convection differ. One holds that bores are capable of suppressing convection away from a mesoscale convective system (MCS) while another holds that low-level convergence is supported by bores near an MCS. This paper investigates buoyancy bore behavior in a mesoscale model simulation using initial and boundary conditions from an actual convective outbreak in the central plains of the United States. Despite low-level forcing produced by colliding outflow boundaries on this day, convection failed to initiate between two MCSs due to mid- to upper-level subsidence. Through manipulation of the convective parameterization scheme within the model, the initiation and suppression of convective heating regions is explicitly controlled. This technique of manual convective initiation allows for a better isolation of the specific sources of thermal forcing. Once the behavioral characteristics of buoyancy bores are ascertained, an analysis of buoyancy bore behavior during the simulated convective outbreak is conducted. The bores suspected of enhancing low-level convergence near MCSs never manifest themselves in the simulations.
Download or read book Internal Gravity Waves and Convection Generated by a Thermal Forcing in the Atmosphere written by Amir Anwar Mohamed Sayed and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Master s Theses Directories written by and published by . This book was released on 2001 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Education, arts and social sciences, natural and technical sciences in the United States and Canada".
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 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 Internal Wave Generation by Convection written by Daniel Lecoanet and published by . This book was released on 2016 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: In nature, it is not unusual to find stably stratified fluid adjacent to convectively unstable fluid. This can occur in the Earth's atmosphere, where the troposphere is convective and the stratosphere is stably stratified; in lakes, where surface solar heating can drive convection above stably stratified fresh water; in the oceans, where geothermal heating can drive convection near the ocean floor, but the water above is stably stratified due to salinity gradients; possible in the Earth's liquid core, where gradients in thermal conductivity and composition diffusivities maybe lead to different layers of stable or unstable liquid metal; and, in stars, as most stars contain at least one convective and at least one radiative (stably stratified) zone. Internal waves propagate in stably stratified fluids. The characterization of the internal waves generated by convection is an open problem in geophysical and astrophysical fluid dynamics. Internal waves can play a dynamically important role via nonlocal transport. Momentum transport by convectively excited internal waves is thought to generate the quasi-biennial oscillation of zonal wind in the equatorial stratosphere, an important physical phenomenon used to calibrate global climate models. Angular momentum transport by convectively excited internal waves may play a crucial role in setting the initial rotation rates of neutron stars. In the last year of life of a massive star, convectively excited internal waves may transport even energy to the surface layers to unbind them, launching a wind. In each of these cases, internal waves are able to transport some quantity--momentum, angular momentum, energy--across large, stable buoyancy gradients. Thus, internal waves represent an important, if unusual, transport mechanism. This thesis advances our understanding of internal wave generation by convection. Chapter 2 provides an underlying theoretical framework to study this problem. It describes a detailed calculation of the internal gravity wave spectrum, using the Lighthill theory of wave excitation by turbulence. We use a Green's function approach, in which we convolve a convective source term with the Green's function of different internal gravity waves. The remainder of the thesis is a circuitous attempt to verify these analytical predictions. I test the predictions of Chapter 2 via numerical simulation. The first step is to identify a code suitable for this study. I helped develop the Dedalus code framework to study internal wave generation by convection. Dedalus can solve many different partial differential equations using the pseudo-spectral numerical method. In Chapter 3, I demonstrate Dedalus' ability to solve different equations used to model convection in astrophysics. I consider both the propagation and damping of internal waves, and the properties of low Rayleigh number convective steady states, in six different equation sets used in the astrophysics literature. This shows that Dedalus can be used to solve the equations of interest. Next, in Chapter 4, I verify the high accuracy of Dedalus by comparing it to the popular astrophysics code Athena in a standard Kelvin-Helmholtz instability test problem. Dedalus performs admirably in comparison to Athena, and provides a high standard for other codes solving the fully compressible Navier-Stokes equations. Chapter 5 demonstrates that Dedalus can simulate convective adjacent to a stably stratified region, by studying convective mixing near carbon flames. The convective overshoot and mixing is well-resolved, and is able to generate internal waves. Confident in Dedalus' ability to study the problem at hand, Chapter 6 describes simulations inspired by water experiments of internal wave generation by convection. The experiments exploit water's unusual property that its density maximum is at 4C, rather than at 0C. We use a similar equation of state in Dedalus, and study internal gravity waves generation by convection in a water-like fluid. We test two models of wave generation: bulk excitation (equivalent to the Lighthill theory described in Chapter 2), and surface excitation. We find the bulk excitation model accurately reproduces the waves generated in the simulations, validating the calculations of Chapter 2.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1989 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Propagation of Internal Gravity Waves in a Thermally Stratified Atmosphere written by Jack Phillip Friedman and published by . This book was released on 1965 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effects of Progressive Waves on Convective Transfer written by Thore Omholt and published by . This book was released on 1970 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermally Non equilibrium Effects on Forced Convection in a Packed Channel written by Curtis Paul Chun and published by . This book was released on 1991 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermal Convection written by Marcello Lappa and published by John Wiley & Sons. This book was released on 2009-11-05 with total page 690 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal Convection - Patterns, Stages of Evolution and Stability Behavior provides the reader with an ensemble picture of the subject, illustrating the state-of-the-art and providing the researchers from universities and industry with a basis on which they are able to estimate the possible impact of a variety of parameters. Unlike earlier books on the subject, the heavy mathematical background underlying and governing the behaviors illustrated in the text are kept to a minimum. The text clarifies some still unresolved controversies pertaining to the physical nature of the dominating driving force responsible for asymmetric/oscillatory convection in various natural phenomena and/or technologically important processes and can help researchers in elaborating and validating new, more complex models, in accelerating the current trend towards predictable and reproducible natural phenomena and in establishing an adequate scientific foundation to industrial processes. Thermal Convection - Patterns, Stages of Evolution and Stability Behavior is intended as a useful reference guide for specialists in disciplines such as the metallurgy and foundry field and researchers and scientists who are now coordinating their efforts to improve the quality of semiconductor or macromolecular crystals. The text may also be of use to organic chemists and materials scientists, atmosphere and planetary physicists, as well as an advanced level text for students taking part in courses on the physics of fluids, fluid mechanics, the behavior and evolution of non-linear systems, environmental phenomena and materials engineering.
Download or read book Convective Organizing and Upscale Development Processes Explored Through Idealized Numerical Experiments written by Stephen Jascourt and published by . This book was released on 1997 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chinese Science Abstracts written by and published by . This book was released on 1987 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Grouping of Clouds and Internal Gravity Waves in a Non hydrostatic Model of Moist Convection written by Xiang-Yu Huang and published by . This book was released on 1991 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of Thermophysics and Heat Transfer written by and published by . This book was released on 1993 with total page 804 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling Atmospheric and Oceanic Flows written by Thomas von Larcher and published by John Wiley & Sons. This book was released on 2014-10-30 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling Atmospheric and Oceanic Flows: Insights from Laboratory Experiments and Numerical Simulations provides a broad overview of recent progress in using laboratory experiments and numerical simulations to model atmospheric and oceanic fluid motions. This volume not only surveys novel research topics in laboratory experimentation, but also highlights recent developments in the corresponding computational simulations. As computing power grows exponentially and better numerical codes are developed, the interplay between numerical simulations and laboratory experiments is gaining paramount importance within the scientific community. The lessons learnt from the laboratory–model comparisons in this volume will act as a source of inspiration for the next generation of experiments and simulations. Volume highlights include: Topics pertaining to atmospheric science, climate physics, physical oceanography, marine geology and geophysics Overview of the most advanced experimental and computational research in geophysics Recent developments in numerical simulations of atmospheric and oceanic fluid motion Unique comparative analysis of the experimental and numerical approaches to modeling fluid flow Modeling Atmospheric and Oceanic Flows will be a valuable resource for graduate students, researchers, and professionals in the fields of geophysics, atmospheric sciences, oceanography, climate science, hydrology, and experimental geosciences.
