Parameter Model Comparison using Closed-loop Simulations of Current and Future Satellite Gravity Missions

The existing observation record of satellite gravity missions spans more than two decades and is already closing in on the minimum time series of 30 years needed to decouple natural and anthropogenic forcing mechanisms according to the Global Climate Observing System (GCOS). The next generation of gravity field missions (GRACE-C, NGGM) are expected to be launched within this decade. These missions as well as their combination (MAGIC) are setting high anticipation for an enhanced monitoring capability that will improve the spatial and temporal resolutions of gravity observations significantly. They will allow an evaluation of long-term trends in the Terrestrial Water Storage (TWS) signal.

This contribution shows numerical closed-loop simulation results of a GRACE-type in-line single-pair missions and MAGIC double-pair missions with realistic noise assumptions for the key payload, tidal and non-tidal background model errors. To enable the analysis of multi-decadal observations, the reduced scale simulation following the acceleration approach are performed. The gravity signal in the simulations is based on modeled mass transport time series of components of the TWS, obtained from future climate projections until the year 2100 following the shared socio-economic pathway scenario 5-8.5 (SSP5-8.5). It evaluates different parameter models, among them the recoverability of long-term climate trends, annual amplitude, and phase of the TWS employing closed-loop numerical simulations of the different constellations. Special emphasis shall be given on the robustness of the estimated TWS long-term-trend for different parameter models applied in different simulation scenarios, systematic changes, as well as on the methodology of the simulation themselves.