Comparison of polar motion excitation series derived from GRACE and from analyses of geophysical fluids

Author: J. Nastula, Rui M. Ponte and David Salstein
Date: 
June 13, 2007
Type: 
Journal Article
Venue: 
Geophysical Research Letters
Citation: 

Nastula, J., R. M. Ponte, and D. A. Salstein (2007), Comparison of polar motion excitation series derived from GRACE and from analyses of geophysical fluids, Geophys. Res. Lett., 34, L11306, doi:10.1029/2006GL028983.

Three sets of degree-2, order-1 harmonics of the gravity field, derived from the Gravity Recovery and Climate Experiment (GRACE) data processed at the Center for Space Research (CSR), Jet Propulsion Laboratory (JPL) and GeoforschungsZentrum (GFZ), are used to compute polar motion excitation functions χ 1 and χ 2. The GFZ and JPL excitations and the CSR χ 2 excitation compare generally well with geodetically observed excitation after removal of effects of oceanic currents and atmospheric winds. The agreement considerably exceeds that from previous GRACE data releases. For the JPL series, levels of correlation with the geodetic observations and the variance explained are comparable to, but still lower than, those obtained independently from available models and analyses of the atmosphere, ocean, and land hydrology. Improvements in data quality of gravity missions are still needed to deliver even tighter constraints on mass-related excitation of polar motion.