Gravity Wave Processes

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.

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

This monograph creates a systematic interpretation of the theoretical and the most actual experimental aspects of the internal wave dynamics in the ocean. Firstly, it draws attention to the important physical effects from an oceanographical point of view which are presented in mathematical descriptions. Secondly, the book serves as an introduction to the range of modern ideas and the methods in the study of wave processes in dispersive media. The book is meant for specialists in physics of the ocean, oceanography, geophysics, hydroacoustics.

This monograph creates a systematic interpretation of the theoretical and the most actual experimental aspects of the internal wave dynamics in the ocean. Firstly, it draws attention to the important physical effects from an oceanographical point of view which are presented in mathematical descriptions. Secondly, the book serves as an introduction to the range of modern ideas and the methods in the study of wave processes in dispersive media. The book is meant for specialists in physics of the ocean, oceanography, geophysics, hydroacoustics.

According to the theory of relativity, we are constantly bathed in gravitational radiation. When stars explode or collide, a portion of their mass becomes energy that disturbs the very fabric of the space-time continuum like ripples in a pond. But proving the existence of these waves has been difficult; the cosmic shudders are so weak that only the most sensitive instruments can be expected to observe them directly. Fifteen times during the last thirty years scientists have claimed to have detected gravitational waves, but so far none of those claims have survived the scrutiny of the scientific community. Gravity's Shadow chronicles the forty-year effort to detect gravitational waves, while exploring the meaning of scientific knowledge and the nature of expertise. Gravitational wave detection involves recording the collisions, explosions, and trembling of stars and black holes by evaluating the smallest changes ever measured. Because gravitational waves are so faint, their detection will come not in an exuberant moment of discovery but through a chain of inference; for forty years, scientists have debated whether there is anything to detect and whether it has yet been detected. Sociologist Harry Collins has been tracking the progress of this research since 1972, interviewing key scientists and delineating the social process of the science of gravitational waves. Engagingly written and authoritatively comprehensive, Gravity's Shadow explores the people, institutions, and government organizations involved in the detection of gravitational waves. This sociological history will prove essential not only to sociologists and historians of science but to scientists themselves.

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.

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.