Time-variable gravity and mass redistribution from synergistic use of GRACE-FO and Chinese gravity satellites

The project „Time-variable gravity and mass redistribution from synergistic use of GRACE-FO and Chinese gravity satellites“ aims at establishing improved time-variable gravity field models. This work is a joint initiative of the National Natural Science Foundation of China (NSFC) and the German Research Foundation (DFG).

Gravity field estimation from the existing GRACE and GRACE-FO missions will be improved, e.g. by optimizing dealiasing signals, refining the noise modeling, accelerometer calibration and optimizing anisotropic filtering techniques. Furthermore, the possibilities of a combination with the upcoming Chinese gravity field mission TianQin-2 will be explored and optimal orbit parameters for TianQin-2 will be determined.

One focus area is the East China Sea. Here, we will isolate the ocean mass change signal over this study region and apply a joint inversion framework to close the regional sea level budget. The contribution of sediment discharge will be accounted for by evaluating oceanic velocities from an ocean model using a Lagrangian approach.

Groundwater storage (GWS) variations will be closely investigated over the North China Plain. First, GWS is calculated by evaluating GRACE(-FO) gravity solutions. For this aim, non-GWS compartments will be removed using global and regional models. An error-estimation considers the uncertainty of measurement errors, post-processing of the gravity field solutions and model errors. Secondly, GWS will directly be inferred from hydrological models. Observations from monitoring wells and GPS stations will be used as independent additional observations.

In this contribution, we will introduce our project and its objectives in more detail. Furthermore, we will show preliminary results regarding ocean mass change in the East China Sea and GWS variations over the North China Plain.