TASMAGOG:

1. Comparison of terrestrial gravity variations from superconducting gravimeters (SG) with a choice of GRACE solutions at 6 European stations 2003-2008 (variances in %) Signal of EOF mode 1 SG - GRACE 2004-2006 Signal fractions of EOF modes 1 – 3 for SG - GRACE time series (SG averaged) SG – GRACE – WGHM 2003-2008 TASMAGOG: Coherence SG – GRACE (example Bad Homburg) • General agreement between gravity variations from SG – GRACE for a choice of GRACE solutions which was evaluated by principal component analysis • Highest correlation between SG and Gaussian filtered GRACE data obtained using filter lengths around 500 km obtained • Result of EOF-analyses: The temporal gravity variations are dominated by the first mode, by > 90% of the signal for the GRACE solutions, by about 65% for the SG time series • Coherence analysis of signal content: high coherence between SG and GRACE time series for periods > 150-180 days (example Bad Homburg)

2. Contributions to theme 1 "Understanding the satellite signals“: Assessment of GRACE-derived gravity field variations by terrestrial SG/AG observations • consistent combination of temporal gravity variations derived from satellite and terrestrial observations • retrieval of a maximum of information • evaluation of the amplitude of the satellite-derived gravity variations against terrestrial observations and • evaluation of the effect of post-processing/filtering/attenuation in comparison to SG gravity changes TASMAGOG/TASMAGROUND:Placement in Themes 1 and 3 - Crosslinking Contributions to theme 3 "Short-term processes“: Quantification of mass variations in continental hydrology from complementary terrestrial (SG) and satellite-based (GRACE) temporal gravity data • gravity variations are interpreted in terms of hydrological mass variations in continental/global water storage • at seasonal/inter-annual times scales and long-term trends • gravity data sets from different climate zones can serve as constraints for global hydrological models • regional quantification of hydrological dynamics • studies of mass transports related to geodynamic processes Crosslinking within SPP 1257:

3. Strasbourg selected worldwide SG stations cluster EU Wettzell TASMAGROUND:Visions – Open Questions - Phase 3 - Open questions • extension to a worldwide set of SG stations in different climate zones • analysis of trends in terrestrial and GRACE-derived gravity variations • clear separation of local/regional/global hydrological gravity effects • gravity data sets as constraints for global hydrological models • further development of a methodology to compare and combine different gravity data, from satellite and SG/terrestrial • combination of geometric (GPS) and gravity data - Visions combination of GRACE and SG gravity variations a broad validation of large-scale hydrological models by combined gravity variations from GRACE and worldwide SG measurements bridging the gap to a GRACE follow-on satellite mission by terrestrial gravity observations Reduction of local hydrological effect for SG records, examples Strasbourg and Wettzell — SG residuals without local hydrological reduction — SG residuals with local hydrological reduction — local hydrological reduction — GRACE GFZ-solution, 330 km filter length