An Investigation of Gravity Wave Saturation Processes in the Lower Stratosphere and Mesosphere PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download An Investigation of Gravity Wave Saturation Processes in the Lower Stratosphere and Mesosphere PDF full book. Access full book title An Investigation of Gravity Wave Saturation Processes in the Lower Stratosphere and Mesosphere by Hua-Guo Chou. Download full books in PDF and EPUB format.
Author: Hua-Guo Chou
Publisher:
ISBN:
Category : Gravity waves
Languages : en
Pages : 188
Get Book Here
Book Description
Author: Hua-Guo Chou
Publisher:
ISBN:
Category : Gravity waves
Languages : en
Pages : 188
Get Book Here
Book Description
Author: Kevin Hamilton
Publisher: Springer Science & Business Media
ISBN: 3642606547
Category : Science
Languages : en
Pages : 568
Get Book Here
Book Description
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.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
Get Book Here
Book Description
This study used the unique data set obtained during the Structure and Atmospheric Turbulence Environment (STATE) experiment, conducted during June 1983 at Poker Flat, Alaska, to examine the structure and characteristics of the wave field near the summer mesopause. It is shown that the rocket and radar data together permit a much more detailed specification of wave parameters than would be possible using either data set alone. Results of this analysis suggest that the wave field near the summer mesopause is composed, in general, of a superposition of wave motions which act collectively to produce regions in which the wave field is convectively or dynamically unstable. These regions are found to correlate well with zones of enhanced turbulence and small-scale wave activity, suggesting the processes and effects of wave field saturation. Keywords: Gravity waves; Instability; Mesosphere; Thermosphere. Reprints.
Author: David C. Fritts
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
Get Book Here
Book Description
Our principal research objectives were to understand the characteristics of and the processes controlling the fluctuations of velocity, density, and optical properties due to wave and turbulence motions in the middle atmosphere. It was hoped that an increased understanding of these motions and their variability would lead to a better predictive capability for their influence on in situ and ground-based systems using this region in the future. Research progress was made on several fronts. Theoretical efforts focussed on wave propagation and saturation processes, the effects of varying stratification on wave saturation and wave transports of energy and momentum, and the influences of chemical recombination on ion and neutral fluctuations due to waves and turbulence. (edc).
Author: PLUMB
Publisher: Birkhäuser
ISBN: 3034858256
Category : Science
Languages : en
Pages : 465
Get Book Here
Book Description
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: E.V. Thrane
Publisher: Springer Science & Business Media
ISBN: 940111594X
Category : Science
Languages : en
Pages : 406
Get Book Here
Book Description
The NATO Advanced Research Workshop on Coupling Processes in the Lower and Middle atmosphere held in Loen, Norway in May 1992 was, in the estimation of apparently all participants, an enormous success. The 18 invited speakers included many of the leaders in the field and resulted in the attendance of a large number of contributing speakers and observers. The subject of the workshop was itself very timely, given the increasing awareness within the international community of the sensitivity of the atmosphere to coupling between adjacent layers, different latitudes, and various scales of motion. It was also very beneficial to bring together researchers with different approaches to the same or similar problems. For example, experimentalists benefitted from the inputs of modelers and theoreticians concerning the needs of current models and the most pressing problems and unknowns. Likewise, theoreticians were challenged to apply themselves to realistic problems and saw their theories tested against geophysical data. These discussions led to meaningful exchanges of ideas and challenges to or displacement of conventional wisdom in some areas. Indeed, possibly the greatest benefit of the workshop was the exposure of many participants to other areas of research or approaches to problems relevant to their own work. Workshop topics were confined to dynamical coupling processes in order to examine progress in a relatively focussed area. Nevertheless, the results presented spanned spatial scales from molecular to global and temporal scales from seconds to decades.
Author: Zhenhua Li
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
In this thesis, investigations on gravity waves are conducted in two regions of the middle atmosphere: the lower stratosphere using high-resolution radiosonde at South Pole and the mesopause region using OH airglow imager at Maui, Hawaii and Cerro Pachon, Chile. Wave characteristics at these regions are deduced and the seasonal variation of wave activity, wave sources, and propagation effect are studied. The study of gravity waves in the lower stratosphere at South Pole reveals that sources other than topography are important even for the lower part of middle atmosphere. Horizontal propagation must be included in parameterization schemes to reflect the fact that waves derived from radiosondes have slant propagation paths. They travel long distance horizontally before they reach higher altitudes. Long term gravity wave characteristics over Maui from 2002 to 2007 are deduced from OH airglow imager. Wave parameters from the long term imager observation provide robust statistics of high-frequency gravity wave in the midlatitudes. Poleward wave propagation preference during summer and equatorward wave propagation preference during winter are observed over Maui. They are also opposite to the seasonal mean meridional wind direction which are always pointing toward winter pole. Momentum fluxes deduced from OH imager are also highly anti-correlated with background winds. At least for the part of spectrum observed by airglow imager, gravity waves act as damping mechanism for diurnal tide. Gravity wave occurrence frequency does not follow the variation of local convective sources and convective sources in a large domain when ducted waves are considered. In fact, with a constant wave source and monthly mean background atmospheric condition, the simulated wave transmission resembles the wave occurrence frequency observed by OH airglow imager at Maui. Thus, at Maui the propagation effect dominates the seasonal variation in wave activity. Gravity wave momentum fluxes deduced from airglow imager provide important observation constraint for gravity wave parameterization for the mesopause region. To explain the cause of seasonal change on meridional propagation preference, three mechanisms are investigated: critical-layer filtering, wave ducting, and Doppler-shifting by local mean wind. Critical-layer filtering failed to explain the propagation preference. Observed gravity wave propagation directions are largely related to the background wind in the airglow layer. This is caused by Doppler-shifting of gravity waves by background wind. Background wind Doppler shifts gravity waves propagating against (along) background wind to higher (lower) frequency and larger (smaller) vertical wavelength. Thus, the observed gravity waves tend to propagate against background wind. The apparent against background wind propagation is largely caused by the contrast in cancellation factor for waves propagate in different direction. To a lesser degree, the difference in dissipation for waves propagate in different direction also contributes to the observed against background wind propagation. The results from this work show gravity wave's propagation in middle atmosphere is strongly affected by atmospheric field. For low frequency waves, their propagation paths are slant and can travel hundreds of kilometers before they reach the middle atmosphere. For high frequency gravity waves, though their propagation paths are mostly vertical, they are subject to ducting and reflection. Due to the large contribution of momentum flux in the Mesosphere and Lower Thermosphere (MLT) by high-frequency, short-horizontal-scale waves, these propagation effects must be included in gravity wave parameterizations.
Author: Bing Cao
Publisher:
ISBN:
Category : Atmospheric physics
Languages : en
Pages : 308
Get Book Here
Book Description
Abstract The mesosphere and lower thermosphere (MLT) (~80-110 km) is dominated by abundant atmospheric waves, of which gravity waves are one of the least understood due to large varieties in wave characteristics as well as potential sources. Gravity waves play an important role in the atmosphere by influencing the thermal balance and helping to drive the global circulation. But due to their sub-grid scale, the effects of gravity waves in General Circulation Models (GCMs) are mostly parameterized. The investigations of gravity waves in this dissertation are from two perspectives: the dynamical processes of gravity wave propagation and dissipation in the MLT region, and the climatology and statistical characteristics of gravity waves as physical basics of gravity wave parameterization. The studies are based on the data acquired from an airglow imager and a sodium lidar, with the assistance of some simulation data from a meso-scale numerical model and GCMs. To understand the dynamical processes in gravity wave propagation and dissipation, a gravity wave should be resolved as fully as possible. The first topic of this dissertation is motivated by the fact that most observational instruments can only capture part of the gravity waves spectrum, either horizontal or vertical structures. Observations from multiple complementary instruments are used to study gravity waves in 3-D space. There are two cases included in this topic. In case 1, a co-located sodium lidar and an airglow imager were used to depict a comprehensive picture of a wave event at altitude between 95-105 km. Thus, the horizontal and vertical gravity waves structures and their ambient atmosphere states were fully characterized, which suggests that a gravity wave undergoes reflection at two different altitudes and near-critical layer filtering in-between. All the retrieved parameters were then applied to a 2-D numerical model whose outputs help to interpret the observations. In case 2, the lidar system is configured in a 5-direction mode, whose laser beams were pointed to zenith and 30° off-zenith at four cardinal directions. Thus, there is a ~50 km separation at 90 km altitude between zenith and any off-zenith directions. Besides the vertical information from traditional lidar measurement pro horizontal wavelength and propagation direction are derived from the phase among measurements in different directions. With a full set of wave and parameters, multiple dispersion validate the goodness of different assumptions involved in linear gravity wave files, differences background and polarization relations are examined and the results theory Better knowledge of gravity waves from observational and numerical, as well as theoretical studies directly contribute to the development of physically-based parameterizations. The second topic of this dissertation is about long-term climatology and statistical characteristics of gravity waves observed by an airglow imager. The results provide some insights on how the source spectrum can be specified and tuning factors are constrained in the parameterization. Results from two sites are compared, one is in the middle of the Pacific Ocean, and the other above the Andes Mountains. The difference and similarity provide some clues to the effects of wave sources and background flow on the gravity wave climatology and intermittency in the mesopause region. Firstly, the long-term climatology of intrinsic wave parameters and propagation direction preferences for high-frequency quasi-monochromatic gravity waves observed by an airglow imager is presented. Wave occurrence and propagation direction are related to convective activities nearby and local background winds. The preferential wave propagation during austral summer is poleward and equatorward during winter. The estimated momentum fluxes show a clear anti-correlation with background winds. Secondly, intermittency of gravity waves near mesopause region is studied. The concept of intermittency is originally from the factors used in wave parameterization schemes to describe the fractional coverage of waves within a large spatial grid and/or temporal period in order to accurately quantify the forcing on the atmosphere by dissipating gravity waves. Intermittency of gravity waves was described by the probability density functions of absolute momentum flux and some diagnostic parameters. An explicit probability function that is a piecewise function of lognormal and power law functions is obtained from airglow data. The relative importance of abundant waves with smaller amplitudes and rare waves with dramatically large amplitudes were compared. Lastly, the duration of gravity waves in the airglow layer is studied. The observed gravity waves duration in the airglow layer is exponentially distributed. Several mechanisms that could lead to such a distribution are put forward from the perspective of wave breaking due to instabilities and blocking due to evanescent regions. Ducted propagation is also a possible factor. Through individual cases and statistical studies, this dissertation investigates the dynamical processes and statistical characteristics of gravity in the MLT region. The results are expected to provide more insight in both observational and modeling research on gravity waves.
Author: R. M. Johnson
Publisher: American Geophysical Union
ISBN: 0875900445
Category : Science
Languages : en
Pages : 354
Get Book Here
Book Description
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 87. This volume provides a review of progress made in recent years in experimental and theoretical investigation of the upper mesosphere and lower thermosphere and coupling between these regions and the ionosphere. Detailed study of the mesosphere/lower thermosphere/ionosphere (MLTI) region has historically been difficult because of its relative inaccessibility to direct measurement techniques and the complex and highly coupled processes which occur there. Although we have still not successfully unraveled all these complex interactions, we have made significant recent progress toward a fuller understanding of the basic state of the MLTI and of the dominant wave and coupling processes. This monograph includes a set of tutorial papers, which review our current understanding of aspects of the MLTI. These tutorials are interspersed with a selection of papers describing research progress on various topics of current interest in this region. The book should therefore be useful both to the newcomer, as an introduction to this field of research, and to the more experienced researcher, providing an overview of research in progress as well as a convenient reference collection of papers describing our current understanding.
Author: Bruce R. Sutherland
Publisher: Cambridge University Press
ISBN: 1316184323
Category : Science
Languages : en
Pages : 395
Get Book Here
Book Description
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.
