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Analysis of the ITSG-GRACE daily models in the determination of polar motion excitation function

Partyka Aleksander, Nastula Jolanta, Śliwińska Justyna, Kur Tomasz, Wińska Małgorzata

Artificial Satellites : Journal of Planetary Geodesy

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2023

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Vol. 58, No. 3

105--121

EN

The main aim of this study is to evaluate the usefulness of Institute of Geodesy at Graz University of Technology (ITSG) daily gravity field models in the determination of hydrological angular momentum (HAM) at nonseasonal time scales. We compared the equatorial components (χ1 and χ2) of HAM calculated with the ITSG daily gravity field models (ITSG-Gravity Recovery and Climate Experiment [ITSG-GRACE] 2016 and ITSG-GRACE 2018) with HAM and sea-level angular momentum (SLAM) from hydrological land surface discharge model (LSDM) and the hydrological signal in the polar motion excitation (known as geodetic residuals [GAO]). Data from ITSG have a daily temporal resolution and allow us to determine oscillations with higher frequencies than the more commonly used monthly data. We limited our study to the period between 2004 and 2011 because of the gaps in GRACE observations before and after this period. We evaluated HAM obtained from ITSG GRACE models in spectral and time domains and determined the amplitude spectra of the analyzed series in the spectral range from 2 to 120 days. Our analyses confirm the existence of a sub-monthly signal in the HAM series determined from ITSG daily data. We observed a similar signal in LSDM-based HAM, but with notably weaker amplitudes. We also observed common peaks around 14 days in the amplitude spectra for the GAO- and ITSG-based series, which may be related to the Earth’s tides. ITSG daily gravity field models can be useful to determine the equatorial components of HAM at nonseasonal time scales.

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Research on Earth rotation and geodynamics in Poland in 2019–2022

Bogusz Janusz, Brzezinski Aleksander, Godah Walyeldeen, Nastula Jolanta

Advances in Geodesy and Geoinformation

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2023

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Vol. 72, no. 2

art. no. e41, 2023

EN

This paper summarizes the activity of the chosen Polish geodetic research teams in 2019–2022 in the fields of the Earth rotation and geodynamics. This publication has been prepared for the needs of the presentation of Polish scientists’ activities on the 28th International Union of Geodesy and Geodynamics General Assembly, Berlin, Germany. The part concerning Earth rotation is mostly focused on the estimation of the geophysical excitation of polar motion using data from Gravity Recovery and Climate Experiment (GRACE) and its follow-on (GRACE-FO) missions, and on the improvement of the determination of Earth rotation parameters based on the Satellite Laser Ranging (SLR), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Global Navigation Satellite System (GNSS) satellite techniques. The part concerning geodynamics is focused on geodetic time series analysis for geodynamical purposes and monitoring of the vertical ground movements induced by mass transport within the Earth’s system, monitoring of the crustal movements using GNSS and newly applied Interferometric Synthetic Aperture Radar (InSAR), discussing the changes of the landslides and its monitoring using geodetic methods as well as investigations of seismic events and sea-level changes with geodetic methods. Finally, the recent research activities carried out by Polish scientists in the international projects is presented.

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Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC): Overview

Śliwińska Justyna, Kur Tomasz, Wińska Małgorzata, Nastula Jolanta, Dobslaw Henryk, Partyka Aleksander

Artificial Satellites : Journal of Planetary Geodesy

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2022

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Vol. 57, Special Issue 1

237--253

EN

Precise positioning and navigation on the Earth’s surface and in space require accurate earth orientation parameters (EOP) data and predictions. In the last few decades, EOP prediction has become a subject of increased attention within the international geodetic community, e.g., space agencies, satellite operators, researchers studying Earth rotation dynamics, and users of navigation systems. Due to this fact, many research centres from around the world have developed dedicated methods for the forecasting of EOP. An assessment of the various EOP prediction capabilities is currently being pursued in the frame of the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC), which began in September 2021 and will be continued until the end of the year 2022. The new campaign was prepared by the EOP PCC Office run by Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN) in Warsaw, Poland, in cooperation with GeoForschungsZentrum (GFZ) and under the auspices of the International Earth Rotation and Reference Systems Service (IERS). In this paper, we provide an overview of the 2nd EOP PCC five months after its start. We discuss the technical aspects and present statistics about the participants and valid prediction files received so far. Additionally, we present the results of preliminary comparisons of different reference solutions with respect to the official IERS 14 C04 EOP series. Root mean square values for different solutions for polar motion, length of day, and precession-nutation components show discrepancies at the level from 0.04 to 0.36 mas, from 0.01 to 0.10 ms, and from 0.01 to 0.18 mas, respectively.

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Globalne prognozowanie

Nastula Jolanta, Czekaj Damian

Geodeta : magazyn geoinformacyjny

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2021

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nr 11

15--17

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Research on Earth rotation and geodynamics in Poland in 2015–2018

Bogusz Janusz, Brzezinski Aleksander, Nastula Jolanta

Geodesy and Cartography

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2019

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Vol. 68, no. 1

65--86

EN

This paper summarizes the activity of the chosen Polish geodetic research teams in 2015–2018 in the fields of Earth: rotation, dynamics as well as magnetic field. It has been prepared for the needs of the presentation on the 27th International Union of Geodesy and Geodynamics General Assembly, Montreal, Canada. The part concerning Earth rotation is mostly focused on the use of modelling of diurnal and subdiurnal components of Earth rotation by including low frequency components of polar motion and UT1 in the analysis, study of free oscillations in Earth rotation derived from both space-geodetic observations of polar motion and the time variation of the second degree gravitational field coefficients derived from Satellite Laser Ranging (SLR) and Gravity Recovery and Climate Experiment (GRACE) observations, new methods of monitoring of Earth rotation, as well as studies on applications of the Ring Laser Gyroscope (RLG) for direct and continuous measurements of changes in Earth rotation and investigations of the hydrological excitation of polar motion. Much attention was devoted to the GRACE-derived gravity for explaining the influence of surface mass redistributions on polar motion. Monitoring of the geodynamical phenomena is divided into study on local and regional dynamics using permanent observations, investigation on tidal phenomena, as well as research on hydrological processes and sea level variation parts. Finally, the recent research conducted by Polish scientists on the Earth’s magnetic field is described.

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Terrestrial water storage variations and their effect on polar motion

Śliwińska Justyna, Wińska Małgorzata, Nastula Jolanta

Acta Geophysica

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2019

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Vol. 67, no. 1

17--39

EN

The role of continental water in polar motion excitation can be illustrated by determining Hydrological Angular Momentum calculated from terrestrial water storage (TWS). In this paper we compare global and regional changes in TWS computed using Coupled Model Intercomparison Project Phase 5 climate models, Global Land Data Assimilation System (GLDAS) land hydrology models and observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. We also compare hydrological excitation functions derived from models with those obtained from the GRACE mission and the hydrological signal in observed polar motion excitation (the so-called geodetic residuals). The results confirm that GLDAS models of seasonal and non-seasonal TWS change are more consistent with GRACE data than climate models; on the other hand, none of the considered models are fully consistent with GRACE data or geodetic residuals. In turn, GRACE observations are most consistent with the non-seasonal hydrological signal in observed excitation. A detailed study of the contribution of different TWS components to the hydrological excitation function shows that soil moisture dominates.