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Author: Christian Bizouard Publisher: Walter de Gruyter GmbH & Co KG ISBN: 3110389134 Category : Science Languages : en Pages : 324
Book Description
Polar motion is an important geophysical process, and difficult to understand given the various parameters involved. But it is of key importance to our climate and climate change. Understanding and modeling also has implications on key technologies such as space geodesy and satellite navigation. Additionally, long term polar motion has close links to decadal climate change and ice cap development. It also reflects the global circulation in the hydro-atmospheric layers and the internal properties of the Earth. Therefore the topic is of primary interest for geophysics as well as climatology.
Author: Christian Bizouard Publisher: Walter de Gruyter GmbH & Co KG ISBN: 3110389134 Category : Science Languages : en Pages : 324
Book Description
Polar motion is an important geophysical process, and difficult to understand given the various parameters involved. But it is of key importance to our climate and climate change. Understanding and modeling also has implications on key technologies such as space geodesy and satellite navigation. Additionally, long term polar motion has close links to decadal climate change and ice cap development. It also reflects the global circulation in the hydro-atmospheric layers and the internal properties of the Earth. Therefore the topic is of primary interest for geophysics as well as climatology.
Author: Christian Bizouard Publisher: Walter de Gruyter GmbH & Co KG ISBN: 3110298090 Category : Science Languages : en Pages : 398
Book Description
Polar motion is an important geophysical process, and difficult to understand given the various parameters involved. But it is of key importance to our climate and climate change. Understanding and modeling also has implications on key technologies such as space geodesy and satellite navigation. Additionally, long term polar motion has close links to decadal climate change and ice cap development. It also reflects the global circulation in the hydro-atmospheric layers and the internal properties of the Earth. Therefore the topic is of primary interest for geophysics as well as climatology.
Author: Lucia Seoane Publisher: ISBN: Category : Earth (Planet) Languages : en Pages : 9
Book Description
Tesseral coefficients C21 and S21 derived from Gravity Recovery and Climate Experiment (GRACE) observations allow to compute the mass term of the polar-motion excitation function. This independent estimation can improve the geophysical models and, in addition, determine the unmodelled phenomena. In this paper, we intend to validate the polar motion excitation derived from GRACE's last release (GRACE Release 4) computed by different institutes: GeoForschungsZentrum (GFZ), Postdam, Germany; Center for Space Research (CSR), Austin, USA; Jet Propulsion Laboratory (JPL), Pasadena, USA, and the Groupe de Recherche en Géodésie Spatiale (GRGS), Toulouse, France. For this purpose, we compare these excitations functions first to the mass term obtained from observed Earth's rotation variations free of the motion term and, second, to the mass term estimated from geophysical fluids models. We confirm the large improvement of the CSR solution, and we show that the GRGS estimate is also well correlated with the geodetic observations. Significant discrepancies exist between the solutions of each centre. The source of these differences is probably related to the data processing strategy. We also consider residuals computed after removing the geophysical models or the gravimetric solutions from the geodetic mass term. We show that the residual excitation based on models is smoother than the gravimetric data, which are still noisy. Still, they are comparable for the X2 component. It appears that X2 residual signals using GFZ and JPL data have less variability. Finally, for assessing the impact of the geophysical fluids models choice on our results, we checked two different oceanic excitation series. We show the significant differences in the residuals correlations, especially for the X1 more sensitive to the oceanic signals.
Author: Florian Seitz Publisher: ISBN: Category : Atmospheric turbulence Languages : en Pages : 11
Book Description
Earth orientation parameters as observed by space-geodetic techniques show a broad spectrum of frequencies. Many efforts have been made to relate spectral peaks to geophysical processes, such as atmospheric or oceanic variations. However, the mechanisms of excitation of some typical oscillations are still unclear. In order to get insight into the rotational dynamics of the Earth, the non-linear gyroscopic Earth model DyMEG has been developed. The present paper studies the superposed effect of atmospheric and oceanic excitation on the free rotation of a viscoelastic gyro. In contrast to former investigations, period and damping of the Earth's free wobble (Chandler wobble) are generated by the gyro from geometrical and rheological parameters. Numerical results for polar motion in the time domain demonstrate that damping exists without explicit excitation but vanishes when regarding atmospheric and oceanic angular momentum. Simulated polar motion for the period from 1975 to 1994 forced by consistent atmospheric and oceanic angular momentum shows significant correlation with geodetic observations which indicates that the free gyroscopic model DyMEG is able to reproduce realistic variations of the Earth's rotation. Spectral analyses of both atmospheric and oceanic excitations give no hint for increased power in the Chandler frequency band as it was stated for the maintenance of the Chandler wobble in recent research studies. Thus, stochastic signals in the climate dynamics as caused by both the weather and oceanic mass redistributions are found to be a sufficient source to maintain the amplitude of the Earth's free wobble by resonant interaction.
Author: Dennis D. McCarthy Publisher: American Geophysical Union ISBN: 0875904599 Category : Science Languages : en Pages : 197
Book Description
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 59. As part of the Nineteenth General Assembly of The International Union of Geodesy and Geophysics Symposium (IUGG) in Vancouver, Canada, Union Symposium U4, "Variations in Earth Rotation" was held August 18-19 1987. The Convenor was Dennis D. McCarthy, U.S. Naval Observatory with P. Paquet, Observatoire Royal de Belgique and M. G. Rochester, St. Johns University serving as co-convernors. In a session on internal structure of the Earth papers dealt with the geophysical effects on Earth rotation parameters. Mantle anelasticity increases the free core nutation (FCN) period by a few days. The period of the FCN and the amplitudes of the main nutation components are sensitive to the ellipticity of the core?]mantle boundary (CMB), and a non-hydrostatic increase of 400m in the flattening of the CMB is a possible explanation of the discrepancies from theory. An alternative suggestion rests on the subseismic description of the nutation spectrum of the stratified liquid core. Evidently new models will have to take into account contributions from the oceans, mantle anelasticity, non-hydrostatic pre-stress, CMB topography and internal core structure.
Author: Tom Herring Publisher: Elsevier ISBN: 0444535799 Category : Science Languages : en Pages : 461
Book Description
Geodesy, which is the science of measuring the size and shape of the Earth, explores the theory, instrumentation and results from modern geodetic systems. The beginning sections of the volume cover the theory of the Earth's gravity field, the instrumentation for measuring the field, and its temporal variations. The measurements and results obtained from variations in the rotation of the Earth are covered in the sections on short and long period rotation hanges. Space based geodetic methods, including the global positioning system (GPS) and Interferometric synthetic aperture radar (SAR), are also examined in detail. Self-contained volume starts with an overview of the subject then explores each topic with in depth detail Extensive reference lists and cross references with other volumes to facilitate further research Full-color figures and tables support the text and aid in understanding Content suited for both the expert and non-expert
Author: Guochang Xu Publisher: Springer Science & Business Media ISBN: 3642117414 Category : Science Languages : en Pages : 507
Book Description
This series of reference books describes sciences of different elds in and around geodesy with independent chapters. Each chapter covers an individual eld and describes the history, theory, objective, technology, development, highlights of research and applications. In addition, problems as well as future directions are discussed. The subjects of this reference book include Absolute and Relative Gravimetry, Adaptively Robust Kalman Filters with Applications in Navigation, Airborne Gravity Field Determination, Analytic Orbit Theory, Deformation and Tectonics, Earth Rotation, Equivalence of GPS Algorithms and its Inference, Marine Geodesy, Satellite Laser Ranging, Superconducting Gravimetry and Synthetic Aperture Radar Interferometry. These are individual subjects in and around geodesy and are for the rst time combined in a unique book which may be used for teaching or for learning basic principles of many subjects related to geodesy. The material is suitable to provide a general overview of geodetic sciences for high-level geodetic researchers, educators as well as engineers and students. Some of the chapters are written to ll literature blanks of the related areas. Most chapters are written by well-known scientists throughout the world in the related areas. The chapters are ordered by their titles. Summaries of the individual chapters and introductions of their authors and co-authors are as follows. Chapter 1 “Absolute and Relative Gravimetry” provides an overview of the gravimetric methods to determine most accurately the gravity acceleration at given locations.
Author: Christian Bizouard
Author: Christian Bizouard
Author: Christian Bizouard
Author: Kurt Lambeck
Author: Lucia Seoane
Author: Florian Seitz
Author: Dennis D. McCarthy
Author: International Polar Motion Service
Author: Tom Herring
Author: Guochang Xu
Author: S. Takagi