Validation of GOCE global gravity eld models using terrestrial gravity data in Norway

The GOCE (Gravity eld and steady-state Ocean Circulation Explorer) satellite gravity gradiometry mission maps the Earth’s gravity eld. Harmonic analysis of GOCE observations provides a global gravity eldmodel (GGFM). Three theoretical strategies, namely the direct, the space-wise and the time-wise approach, have been proposed for GOCE harmonic analysis. Based on these threemethods, several GGFMs have been provided to the user community by ESA. Thereby different releases are derived from different periods of GOCE observations and some of themodels are based on combinations with other sources of gravity eld information. Due to themultitude of GOCE GGFMs, validation against independent data is a crucial task for the quality description of the different models. In this study, GOCE GGFMs from three releases are validated with respect to terrestrial free-air gravity anomalies in Norway. The spectral enhancement method is applied to avoid spectral inconsistency between the terrestrial and the GOCE free-air gravity anomalies. The results indicate that the time-wise approach is a reliable harmonic analysis procedure in all three releases of GOCEmodels. The spacewise approach, available in two releases, provides similar results as the time-wise approach. The direct approach seems to be highly affected by a-priori information.