EGU24-8315, updated on 08 Mar 2024
https://doi.org/10.5194/egusphere-egu24-8315
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Exploiting the SLR+GRACE/GRACE-FO Hybrid Solutions to Determine Gravimetric Excitations of Polar Motion

Jolanta Nastula1, Justyna Śliwińska-Bronowicz1, Małgorzata Wińska2, and Aleksander Partyka1
Jolanta Nastula et al.
  • 1Centrum Badań Kosmicznych PAN, Warsaw, Poland, (nastula@cbk.waw.pl)
  • 2Warsaw University of Technology, Faculty of Civil Engineering, Warsaw, Poland

In this study, we investigate the excitation of polar motion (PM) caused by changes in the distribution of hydrosphere mass. This phenomenon is expressed through hydrological angular momentum (HAM) series, which can be estimated using global models of the continental hydrosphere, Earth's gravity field variations, and numerical climate models.

The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions have provided crucial data for understanding the time-variable gravity field affected by changes in global mass distribution. These missions also reveal how mass variations in the continental hydrosphere and cryosphere affect PM. However, it has been identified that GRACE/GRACE-FO solutions have certain limitations when determining geopotential coefficients of lower degrees. As a remedy, it has become standard practice to replace the C20 values obtained from GRACE/GRACE-FO solutions with corresponding estimates from Satellite Laser Ranging (SLR). Similar substitutions are also recommended for the C21 and S21 coefficients.

In our study, we employ hybrid SLR+GRACE/GRACE-FO time-variable gravity solutions, made available by the Institute of Geodesy at Graz University of Technology (ITSG) and Centre National D'Etudes Spatiales (CNES), to determine hydrological/gravimetric angular momentum (HAM). To evaluate the SLR+GRACE/GRACE-FO-based HAM series, we compare them with the hydrological signal in observed PM excitation, referred to as geodetic residuals (or GAO). Additionally, we compare these series with HAM derived from GRACE/GRACE-FO data, focusing on seasonal and non-seasonal variations.

Our findings indicate that the excitation functions derived from the hybrid solution closely align with the GAO. In fact, they are similar or even better consistent with GAO than the series derived from the GRACE/GRACE-FO data.

How to cite: Nastula, J., Śliwińska-Bronowicz, J., Wińska, M., and Partyka, A.: Exploiting the SLR+GRACE/GRACE-FO Hybrid Solutions to Determine Gravimetric Excitations of Polar Motion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8315, https://doi.org/10.5194/egusphere-egu24-8315, 2024.