Comparison of geodetic hydrological excitation functions with new GRACE RL06 solutions and hydrological excitations
Abstract
The determination of Earth rotation parameters that include precession/nutation, polar motion and length-of-day variations is a very important task in present-day geodesy. The changes in orientation of the Earth's rotational axis, known as polar motion, is excited by constantly changing mass distribution in the geophysical fluids (atmosphere, ocean, land hydrosphere). This mass redistribution movements excite the Earth's rotational changes primarily at seasonal and shorter time scales.
The 2002 launch of the GRACE (Gravity Recovery and Climate Experiment) twin satellites has made available several time series of geopotential coefficients. The GRACE measurements reflect mass transports in atmosphere, oceans, and land water and make it possible to deal with the mass balance budget in atmospheric, oceanic and hydrological models. Here, the latest release of GRACE gravity field coefficients (Release 06, RL06) are evaluated for polar motion applications. Data have been processed using new background models (ocean tide model FES2014) and Atmosphere and Ocean De-aliasing Level 1B (AOD1B RL06) Product. An assessment of the impact of hydrological effects on polar motion, through seasonal soil moisture changes, ice and snow loading and melting, is based on the determination of geodetic residuals (GAO). Being a difference between Geodetic Angular Momentum (GAM) and the sum of Atmospheric and Oceanic Angular Momentum (AAM and OAM, respectively), GAO reflect hydrological signals in observed polar motion excitation. Here, we would like to compare the results of geodetic hydrological excitation functions that are computed by removing modelled atmospheric and oceanic effects from precise observations of polar motion excitations. We compare the resulting geodetic residuals with hydrological excitation functions based on new GRACE RL06 solutions as well as oldest version - RL05, and with hydrological models. The polar motion budged is analysed here at different time scales - decadal, inter-annual, seasonal and short term oscillations. In this study, we use various GRACE time series of Earth's gravity field coefficients as well as different atmospheric, oceanic and hydrological model outputs to achieve better agreement between geodetic observations and geophysical excitation functions of polar motion.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G31B0662S
- Keywords:
-
- 1239 Earth rotation variations;
- GEODESY AND GRAVITYDE: 1240 Satellite geodesy: results;
- GEODESY AND GRAVITYDE: 1241 Satellite geodesy: technical issues;
- GEODESY AND GRAVITYDE: 5450 Orbital and rotational dynamics;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS