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Jolanta Nastula - One of the best experts on this subject based on the ideXlab platform.

  • Hydrological excitation of Polar Motion by different variables from the GLDAS models
    Journal of Geodesy, 2017
    Co-Authors: Malgorzata Winska, Jolanta Nastula, David Salstein
    Abstract:

    Continental hydrological loading by land water, snow and ice is a process that is important for the full understanding of the excitation of Polar Motion. In this study, we compute different estimations of hydrological excitation functions of Polar Motion (as hydrological angular momentum, HAM) using various variables from the Global Land Data Assimilation System (GLDAS) models of the land-based hydrosphere. The main aim of this study is to show the influence of variables from different hydrological processes including evapotranspiration, runoff, snowmelt and soil moisture, on Polar Motion excitations at annual and short-term timescales. Hydrological excitation functions of Polar Motion are determined using selected variables of these GLDAS realizations. Furthermore, we use time-variable gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE) to determine the hydrological mass effects on Polar Motion excitation. We first conduct an intercomparison of the maps of variations of regional hydrological excitation functions, timing and phase diagrams of different regional and global HAMs. Next, we estimate the hydrological signal in geodetically observed Polar Motion excitation as a residual by subtracting the contributions of atmospheric angular momentum and oceanic angular momentum. Finally, the hydrological excitations are compared with those hydrological signals determined from residuals of the observed Polar Motion excitation series. The results will help us understand the relative importance of Polar Motion excitation within the individual hydrological processes, based on hydrological modeling. This method will allow us to estimate how well the Polar Motion excitation budget in the seasonal and inter-annual spectral ranges can be closed.

  • Oceanic excitation of Polar Motion: Identification of specific oceanic areas important for Polar Motion excitation
    Journal of Geodynamics, 2012
    Co-Authors: Jolanta Nastula, Richard S. Gross, David A. Salstein
    Abstract:

    Abstract In this paper regional values of the oceanic excitation function of Polar Motion are computed from bottom pressure and oceanic current fields from the ECCO/JPL data-assimilating model kf080 for the period 1993–2009. The influence of different geographic regions of the ocean on the excitation of Polar Motion is determined by calculating correlations and covariances between these regional excitations and either the global non-atmospheric excitation or the global oceanic excitation. The non-atmospheric excitation is estimated by subtracting the atmospheric signal from the excitation computed from geodetic observations of Polar Motion; the global oceanic excitation function is equivalent to the sum of the oceanic excitation function computed in every grid point. Our attention focuses on the regional distribution of the oceanic Polar Motion excitation for two time scales: the seasonal spectral band and the band around the Chandler period. We identified the southern Indian Ocean and the South Pacific Ocean as important regions for non-atmospheric Polar Motion excitation. The maximum of variability over the southern Indian Ocean is especially important in the case of annual oscillation. The Atlantic Ocean makes less significant contribution to the non-atmospheric Polar Motion excitation than the Pacific and Indian Ocean in both considered spectral ranges. Inland seas like the Mediterranean and the Sea of Japan have high covariance with the global signals.

  • hydrological excitation of Polar Motion derived from grace gravity field solutions
    International Journal of Geophysics, 2011
    Co-Authors: L. Seoane, Jolanta Nastula, Christian Bizouard, D. Gambis
    Abstract:

    The influence of the continental water storage on the Polar Motion is not well known. Different models have been developed to evaluate these effects and compared to geodetic observations. However, previous studies have shown large discrepancies mainly attributed to the lack of global measurements of related hydrological parameters. Now, from the observations of the GRACE mission, we can estimate the Polar Motion excitation due to the global hydrology. Data processing of GRACE data is carried out by several centers of analysis, we focus on the new solution computed by the Groupe de Recherche de Geodesie Spatiale. At annual scales, excitations derived from GRACE data are in better agreement with geodetic observations than models estimates. The main contribution to the hydrological excitation comes from the monsoon climates regions where GRACE and models estimates are in a very good agreement. Still, the effect of the north high latitudes regions, where the principal areas of snow cover are found, cannot be neglected. At these regions, GRACE and models estimated contributions to Polar Motion excitations show significant discrepancies. Finally, GRACE-based excitations reveal the possible influence of water storage variations in exciting Polar Motion around the frequency of 3 cycles per year.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    Here we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experimentGRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that 3 models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    Abstract Here we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experiment GRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that three models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion.

Barbara Kołaczek - One of the best experts on this subject based on the ideXlab platform.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    Here we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experimentGRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that 3 models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    Abstract Here we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experiment GRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that three models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    International audienceHere we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experimentGRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that 3 models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion

  • El Nino-related variations in atmosphere-Polar Motion interactions
    Journal of Geodynamics, 2003
    Co-Authors: Barbara Kołaczek, Jolanta Nastula, David A. Salstein
    Abstract:

    Abstract The influence of El Nino phenomena on the correlation between atmospheric and geodetic excitation functions of Polar Motion during four decades, from 1962 to 2000, is studied. These correlations are computed in three different spectral ranges of Polar Motion variations, namely 90–150, 150–230 and 230–450 days, which include the 120-day, semiannual, and annual oscillations, respectively. These correlation coefficients are variable in all spectra ranges. They are the most stable in the case of the annual oscillation, reaching maxima of about 0.9. In the case of the semiannual oscillation they are more variable, especially before 1970, and they reach maximum values of 0.8–0.9. In the case of the 120-day oscillation, correlation coefficients are the most variable, though more stable after 1980. The disturbances of correlation coefficients between atmospheric and geodetic excitation functions of Polar Motion are highly correlated with the epochs of El Nino/La Nina phenomena in the most cases, suggesting that during these events, non-atmospheric effects, such as those in the ocean, also have an influence on Polar Motion.

Clark R. Wilson - One of the best experts on this subject based on the ideXlab platform.

  • Seasonal excitation of Polar Motion
    Journal of Geodynamics, 2012
    Co-Authors: Jianli Chen, Clark R. Wilson, Yonghong Zhou
    Abstract:

    We estimate geophysical excitations (chi(1) and chi(2)) of Polar Motion using multiple sources of data, including recent atmospheric, oceanic, and hydrological models, satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE), and compare geophysical excitations with observed Polar Motion excitations from space geodetic techniques. At seasonal time scales, both model-estimated excitations from the geophysical fluids envelope (i.e., atmosphere, ocean, and hydrosphere) and GRACE-observed excitations agree remarkably well with Polar Motion observations in the chi(2) component, and in the chi(1) component, model estimates and observed geodetic excitations show significant discrepancies. However, mass excitations estimated from GRACE show significantly better agreement with observed excitations than those from models, especially in chi(1). due to better quantification of terrestrial water storage and oceanic mass changes using GRACE data. Furthermore. GRACE satellite gravity measurements offer a unique means for quantifying contributions from cryospheric angular momentum (CAM) change, a component mostly neglected in previous studies due to the lack of adequate observations or reliable ice sheets models. Based on GRACE estimates, CAM excitations appear a minor, but not negligible contributor to seasonal excitations of Polar Motion. The significantly better agreement in chi(2) (than that in chi(1)) between observations and model excitations is related to the higher sensitivity of chi(2) excitations to atmospheric pressure and terrestrial water changes over the Eurasia and North American continents, because of the special relationship between the Delta S-21 spherical harmonic coefficient (proportional to chi(2)) mass model and the locations of the two continents. (C) 2011 Elsevier Ltd. All rights reserved.

  • On long-period Polar Motion
    Journal of Geodesy, 2002
    Co-Authors: R. O. Vicente, Clark R. Wilson
    Abstract:

    Five separate Polar Motion series are examined in order to understand what portion of their variations at periods exceeding several years represents true Polar Motion. The data since the development of space-geodetic techniques (by themselves insufficient for study of long-period Motion), and a variety of historical astrometric data sets, allow the following tentative conclusions: retrograde long-period Polar Motion below about −0.2 cpy (cycles per year) in pre-space-geodetic data (pre-1976) is dominantly noise. For 1976–1992, there is poor agreement between space-geodetic and astrometric series over the range −0.2 to +0.2 cpy, demonstrating that classical astrometry lacked the precision to monitor Polar Motion in this frequency range. It is concluded that all the pre-1976 astrometric Polar Motion data are likely to be dominated by noise at periods exceeding about 10 years. The exception to this is possibly a linear trend found in some astrometric and space geodetic series. At frequencies above prograde +0.2 cpy (periods shorter than about 5 years), historical astrometric data may be of sufficient quality for comparisons with geophysical excitation time series. Even in the era of space geodesy, significant differences are found in long-period variations in published Polar Motion time series.

  • hydrological and oceanic excitations to Polar Motion andlength of day variation
    Geophysical Journal International, 2000
    Co-Authors: Jianli Chen, Clark R. Wilson, Ben F. Chao, C. K. Shum, Byron D Tapley
    Abstract:

    SUMMARY Water mass redistributions in the global hydrosphere, including continental water storage change and non-steric sea level change, introduce variations in the hydrological angular momentum (HAM) and the oceanic angular momentum (OAM). Under the conservation of angular momentum, HAM and OAM variations are signi¢cant excitation sources of the Earth rotational variations at a wide range of timescales. In this paper, we estimate HAM and OAM variations and their excitations to Polar Motion and length-of-day variation using soil moisture and snow estimates and non-steric sea level change determined by TOPEX/Poseidon satellite radar altimeter observations and a simpli¢ed steric sea level change model. The results are compared with the variations of Polar Motion and LOD that are not accounted for by the atmosphere. This study indicates that seasonal continental water storage change provides signi¢cant contributions to both Polar Motion and LOD variation, especially to Polar Motion X, and the non-steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies, particularly in Polar Motion Y and LOD. The good correlation between OAM contributions and the remaining excitations shows that large-scale non-tidal mass variation exists in the oceans and can be detected by TOPEX/Poseidon altimeter observations.

  • Excitation of Polar Motion
    International Astronomical Union Colloquium, 2000
    Co-Authors: Clark R. Wilson
    Abstract:

    AbstractConceptual models of Polar Motion have evolved over the past century, as improved data revealed signals over progressively wider frequency bands. In the 1890s, Chandler represented Polar Motion as a sum of discrete components, 14 month and annual terms, and this component model effectively summarized the observations, but did not provide a physical explanation for them. Over time both the search for a physical understanding of Polar Motion, and the ability to observe the broad band continuum outside the Chandler and annual bands have led to an understanding of Polar Motion as a continuum of variations, not adequately described by a few discrete components. The continuum concept is now the working model in most studies of Polar Motion. The transition from component to continuum conceptual models preceded the arrival of high quality data by several decades, and reflected significant contributions from Harold Jeffreys. With modern space geodetic observations and good global numerical models of the atmosphere, oceans, and other climate processes, it is clear that air and water Motion and redistribution are the dominant contributors to the excitation continuum.

  • Hydrological and oceanic excitations to Polar Motion andlength‐of‐day variation
    Geophysical Journal International, 2000
    Co-Authors: Jianli Chen, Clark R. Wilson, Ben F. Chao, C. K. Shum, Byron D Tapley
    Abstract:

    SUMMARY Water mass redistributions in the global hydrosphere, including continental water storage change and non-steric sea level change, introduce variations in the hydrological angular momentum (HAM) and the oceanic angular momentum (OAM). Under the conservation of angular momentum, HAM and OAM variations are signi¢cant excitation sources of the Earth rotational variations at a wide range of timescales. In this paper, we estimate HAM and OAM variations and their excitations to Polar Motion and length-of-day variation using soil moisture and snow estimates and non-steric sea level change determined by TOPEX/Poseidon satellite radar altimeter observations and a simpli¢ed steric sea level change model. The results are compared with the variations of Polar Motion and LOD that are not accounted for by the atmosphere. This study indicates that seasonal continental water storage change provides signi¢cant contributions to both Polar Motion and LOD variation, especially to Polar Motion X, and the non-steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies, particularly in Polar Motion Y and LOD. The good correlation between OAM contributions and the remaining excitations shows that large-scale non-tidal mass variation exists in the oceans and can be detected by TOPEX/Poseidon altimeter observations.

Jianli Chen - One of the best experts on this subject based on the ideXlab platform.

  • Seasonal excitation of Polar Motion
    Journal of Geodynamics, 2012
    Co-Authors: Jianli Chen, Clark R. Wilson, Yonghong Zhou
    Abstract:

    We estimate geophysical excitations (chi(1) and chi(2)) of Polar Motion using multiple sources of data, including recent atmospheric, oceanic, and hydrological models, satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE), and compare geophysical excitations with observed Polar Motion excitations from space geodetic techniques. At seasonal time scales, both model-estimated excitations from the geophysical fluids envelope (i.e., atmosphere, ocean, and hydrosphere) and GRACE-observed excitations agree remarkably well with Polar Motion observations in the chi(2) component, and in the chi(1) component, model estimates and observed geodetic excitations show significant discrepancies. However, mass excitations estimated from GRACE show significantly better agreement with observed excitations than those from models, especially in chi(1). due to better quantification of terrestrial water storage and oceanic mass changes using GRACE data. Furthermore. GRACE satellite gravity measurements offer a unique means for quantifying contributions from cryospheric angular momentum (CAM) change, a component mostly neglected in previous studies due to the lack of adequate observations or reliable ice sheets models. Based on GRACE estimates, CAM excitations appear a minor, but not negligible contributor to seasonal excitations of Polar Motion. The significantly better agreement in chi(2) (than that in chi(1)) between observations and model excitations is related to the higher sensitivity of chi(2) excitations to atmospheric pressure and terrestrial water changes over the Eurasia and North American continents, because of the special relationship between the Delta S-21 spherical harmonic coefficient (proportional to chi(2)) mass model and the locations of the two continents. (C) 2011 Elsevier Ltd. All rights reserved.

  • Excitation of Annual Polar Motion by the Pacific, Atlantic and Indian Oceans
    Chinese Journal of Astronomy and Astrophysics, 2007
    Co-Authors: Yonghong Zhou, De Chun Liao, Jianli Chen
    Abstract:

    The global oceans play important roles in exciting the annual Polar Motion besides the atmosphere. However, it is still unclear about how large the regional oceans contribute to the annual Polar Motion. We investigate systemically the contributions of the Pacific, Atlantic and Indian Oceans to the excitation of the annual Polar Motion, based on the output data of ocean current velocity field and ocean bottom pressure field from "Estimating the Circulation and Climate of the Ocean (ECCO)" ocean circulation model over the period 1993-2005. The result shows that due to its particular location and shape, the Atlantic Ocean makes a less significant contribution to the x-component of the annual Polar Motion excitation than the Pacific and Indian Oceans, while all these three oceans contribute to the y-component of the annual Polar Motion excitation to some extent.

  • hydrological and oceanic excitations to Polar Motion andlength of day variation
    Geophysical Journal International, 2000
    Co-Authors: Jianli Chen, Clark R. Wilson, Ben F. Chao, C. K. Shum, Byron D Tapley
    Abstract:

    SUMMARY Water mass redistributions in the global hydrosphere, including continental water storage change and non-steric sea level change, introduce variations in the hydrological angular momentum (HAM) and the oceanic angular momentum (OAM). Under the conservation of angular momentum, HAM and OAM variations are signi¢cant excitation sources of the Earth rotational variations at a wide range of timescales. In this paper, we estimate HAM and OAM variations and their excitations to Polar Motion and length-of-day variation using soil moisture and snow estimates and non-steric sea level change determined by TOPEX/Poseidon satellite radar altimeter observations and a simpli¢ed steric sea level change model. The results are compared with the variations of Polar Motion and LOD that are not accounted for by the atmosphere. This study indicates that seasonal continental water storage change provides signi¢cant contributions to both Polar Motion and LOD variation, especially to Polar Motion X, and the non-steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies, particularly in Polar Motion Y and LOD. The good correlation between OAM contributions and the remaining excitations shows that large-scale non-tidal mass variation exists in the oceans and can be detected by TOPEX/Poseidon altimeter observations.

  • Hydrological and oceanic excitations to Polar Motion andlength‐of‐day variation
    Geophysical Journal International, 2000
    Co-Authors: Jianli Chen, Clark R. Wilson, Ben F. Chao, C. K. Shum, Byron D Tapley
    Abstract:

    SUMMARY Water mass redistributions in the global hydrosphere, including continental water storage change and non-steric sea level change, introduce variations in the hydrological angular momentum (HAM) and the oceanic angular momentum (OAM). Under the conservation of angular momentum, HAM and OAM variations are signi¢cant excitation sources of the Earth rotational variations at a wide range of timescales. In this paper, we estimate HAM and OAM variations and their excitations to Polar Motion and length-of-day variation using soil moisture and snow estimates and non-steric sea level change determined by TOPEX/Poseidon satellite radar altimeter observations and a simpli¢ed steric sea level change model. The results are compared with the variations of Polar Motion and LOD that are not accounted for by the atmosphere. This study indicates that seasonal continental water storage change provides signi¢cant contributions to both Polar Motion and LOD variation, especially to Polar Motion X, and the non-steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies, particularly in Polar Motion Y and LOD. The good correlation between OAM contributions and the remaining excitations shows that large-scale non-tidal mass variation exists in the oceans and can be detected by TOPEX/Poseidon altimeter observations.

  • Discrete Polar Motion equations for high frequencies
    Journal of Geodesy, 1996
    Co-Authors: Clark R. Wilson, Jianli Chen
    Abstract:

    We examine several digital filter methods designed to accurately estimate excitation axis variations from observed Polar Motion at frequencies exceeding 1 cycle per day. These methods are developed from a discrete time series filter equation originally presented in 1940 by Harold Jeffreys, and subsequently revised over the past two decades. The filters derived here provide improved amplitude accuracy at the highest frequencies now observable in space geodetic Polar Motion data.

Aleksander Brzeziński - One of the best experts on this subject based on the ideXlab platform.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    Here we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experimentGRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that 3 models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    Abstract Here we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experiment GRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that three models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion.

  • Seasonal excitation of Polar Motion estimated from recent geophysical models and observations
    Journal of Geodynamics, 2009
    Co-Authors: Aleksander Brzeziński, Jolanta Nastula, Barbara Kołaczek
    Abstract:

    International audienceHere we investigate the seasonal excitation balance of Polar Motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experimentGRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of Polar Motion. Comparison shows that 3 models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the Motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of Polar Motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of Polar Motion

  • Oceanic excitation of Polar Motion and nutation: an overview
    2003
    Co-Authors: Aleksander Brzeziński
    Abstract:

    Exchanges of the angular momentum between the atmosphere, the ocean and the solid Earth have an important impact on Polar Motion at periods from a fraction of a day to years and contribute significantly to nutation. But while the role of the atmosphere in the excitation balance is well established, the importance of the ocean has been recognized only recently. This paper gives an overview of the non-tidal oceanic excitation of Polar Motion and nutation by taking into account recent advances in modeling the oceanic angular momentum.