Overview of the reprocessed GFZ RL07 GRACE/GRACE-FO Level-2 time series

Being part of the GRACE/GRACE-FO Science Data System, the GFZ Helmholtz Centre for Geosciences is one of the official Level-2 processing centers routinely providing monthly gravity field models. From these models, mass changes at the Earth’s surface can be inferred and a wide range of geoscientists make use of them to study climate related phenomena. Meanwhile, GFZ’s operationally processed monthly gravity fields have been based on release 6 (RL06) processing standards since 2018. However, several processing improvements were already developed during this period, mostly within the Research Unit “New Refined Observations of Climate Change from Spaceborne Gravity Missions” (NEROGRAV) funded by the German Research Foundation DFG. As a result, GFZ now releases a reprocessed and improved RL07 time series.

When developing the new GFZ RL07 processing standards, the main focus was on an optimized stochastic modeling during the GRACE/GRACE-FO gravity field determination. This includes the extension of the stochastic instrument error models, the optimization of the combination of the different observations in terms of relative weighting, and the inclusion of temporally changing non-tidal background model error variance-covariance matrices in the adjustment process. Further changes compared to GFZ RL06 comprise the parameterization as well as the applied background models, e.g., the ocean tide model and the static gravity field model.

This presentation provides an overview of the GFZ RL07 performance compared to RL06 as well as to the latest releases of other processing centers. Improvements stemming from the applied advanced processing strategy lead to a significant reduction of noise (> 30% relative to GFZ RL06), as well as more realistic formal uncertainties of the estimated gravity field parameters.