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

目前，中国正在准备一对重力卫星(天琴二号)，它将实现非常类似于GRACE-FO的领导者-追随者概念。如果获得批准，天琴二号很可能在格雷斯-FO仍在轨道上时进入运行阶段。在这里，我们建议(1)在仪器处理层面(中国组)和后处理层面(德国组)改进重力建模技术，(2)通过模拟优化天琴二号轨道，假定它可以与GRACE-FO一起飞行，以及(3)在空间分辨率起关键作用的两个重要应用中改进GRACE-FO的质量再分布估计，并评估如果与GRACE-FO并行飞行，调整天琴二号轨道的潜在好处。对于(3)，我们将处理东中国海的区域海平面预算，这是一个边缘海洋地区，海平面上升高于平均水平，可能会产生巨大的生态、经济和政治后果，并且假设河流沉积的变化对该地区有很大贡献。第二个区域是中国平原北部，这是中国笔下人口最稠密和农业最重要的地区之一，在那里观察到了巨大的信号，并将其归因于地下水抽水。

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.