G04 Earth Rotation and Geodynamics

IAG (Geodesy)

30-Jun-2015, 15:00 - 16:30

Abstract content:

Hydrological excitation functions determined from GRACE, SLR and GNSS data

The comparison of the Hydrological Angular Momentum (HAM) with hydrological signal in observed geodetic excitation functions is a common method of assessing the influence of land hydrology on polar motion excitation function.

This hydrological signal is estimated as differences between observed geodetic excitation functions (Geodetic Angular Momentum, GAM) and a sum of Atmospheric Angular Momentum (AAM) and Oceanic Angular Momentum (OAM).

HAM can be estimated either from global models of land hydrosphere or from harmonics coefficients Cnm, Snm of the Earth’s gravity field.

We compare several sets of degree-2, order-1 harmonics of the Earth’s gravity field, derived from the Gravity Recovery and Climate Experiment (GRACE), Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS) data. We use the degree-2 coefficients to estimate gravimetric polar motion excitation functions χ1 and χ2. Additionally, the global models of land hydrology such as Global Land Data Assimilation Systems (GLDAS), which contain information about water mass redistributions in the global hydrosphere, are used to estimate hydrological polar motion excitation functions χ1 and χ2.

The aim of this study is to determine the optimum model of the hydrological angular momentum (HAM) by finding the best agreement between the values derived from geodetic observations and different combination of the hydrological excitation functions.

Our algorithm is based on a fit of hydrological excitation functions to geodetic residuals using the least-square method.

J. Nastula1, M. Winska2, K. Sosnica3, M. Birylo4.
1Space Research Centre, Polish Academy of Sciences, Warsaw, Poland.
2Warsaw University of Technology, Faculty of Civil Engineering-The Division of Engineering Surveying, Warsaw, Poland.
3University of Bern, Astronomical Institute, Bern, Switzerland.
4University of Warmia and Mazury, Faculty of Geodesy- Geospatial and Civil Engineering, Olsztyn, Poland.


GRACE, GNSS, SLR data     hydrological excitation functions