Advanced processing strategies for a future GFZ GRACE/GRACE-FO Level-2 data release

Being part of the GRACE/GRACE-FO Science Data System, the GFZ German Research Centre for Geosciences is one of the official Level-2 processing centers routinely providing monthly gravity field models. These models are used by a wide variety of geoscientists to infer mass changes mainly at the Earth’s surface. Currently, the operationally processed monthly gravity fields are still based on release 6 (RL06) standards, but developments in view of a reprocessed and improved GFZ RL07 time series are already ongoing. Most of these improvements have been developed within the Research Unit “New Refined Observations of Climate Change from Spaceborne Gravity Missions” (NEROGRAV) funded by the German Research Foundation DFG. After a successful first phase, the second three years phase of NEROGRAV has started last year. At present, we primarily work towards the completion of an optimized stochastic modeling for GRACE and GRACE-FO gravity field determination. This includes the extension of the stochastic instrument error models, the optimization of the combination of the different observations, and the inclusion of tidal and temporally changing non-tidal background model error variance-covariance matrices in the adjustment process. This presentation provides an overview of the main outcomes of these advanced processing strategies. We discuss details on stochastic modeling of non-tidal atmospheric-oceanic background models including the assessment of temporal correlations and will present preliminary RL07 Level-2 results in the spectral and spatial domain in comparison with the standard GFZ GRACE/GRACE-FO RL06 time series.