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

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Currently, China prepares for a pair of gravity satellites (TianQin-2) which would realize a leader-follower concept very similar to GRACE-FO. If approved, TianQin-2 may very well reach its operational phase when GRACE-FO is still in orbit. Here we propose (1) to improve gravity modelling techniqes both at instrument processing level (Chinese group) and in the postprocessing (German group), (2) to optimize the TianQin-2 orbit through simulations, assuming it can be flown in conjunction with GRACE-FO, and (3) to improve mass redistribution estimates from GRACE-FO in two important applications where spatial resolution plays a key role, and assess the potential benefit of adjusting the TianQin-2 orbit if flown in parallel with GRACE-FO. For (3) we will address the regional sea level budget in the East China Sea, a marginal ocean region where sea level rise is above-average with potentiallytremendous ecological, economical and political consequences, and where a large contributions from changes in river sedimentation is hypothesized. The second region is the North China Plain, one of China’s most densely populated and agricultarally important areas and where large signals have been observed and ascribed to groundwater withdrawals.