Updating Esa's Earth System Model of the Time-Variable Gravity Field for Future Mission Simulation Studies
Wednesday, 17 December 2014
The ability of any satellite gravity mission concept to monitor mass transport processes in the Earth system is typically tested well ahead of its implementation by means of detailed simulation studies. Those studies often extend from the simulation of realistic orbits and instrumental data all the way down to the retrieval of global gravity field solution time-series, thereby requiring realistic representations of the spatio-temporal mass variability in the different sub-systems of the Earth as a source model for the orbit computations.
For such simulations, a suitable source model is required to (i) represent rapid mass motions in for example the atmosphere and oceans, in order to realistically include the effects of temporal aliasing due to non-tidal high-frequency mass variability into the retrieved gravity fields. Moreover, (ii) low-frequency variability needs to present at realistic amplitudes and frequencies at in particular small spatial scales, in order to assess to what extent a new mission concept might provide further insight into physical processes not observed by a satellite system before.
The new source model presented in this study attempts to fulfill both requirements: Based on ECMWF's recent atmospheric reanalysis ERA Interim and corresponding simulations from numerical models of the other Earth system components, it offers spherical harmonic coefficients of the mass variability in atmosphere, oceans, the terrestrial hydrosphere including the ice-sheets and glaciers, as well as the solid Earth with high temporal (6 hours) and spatial (d/o 180) resolution for a period of 12 years. Together with the source model, a corresponding de-aliasing model for atmospheric and oceanic high-frequency variability that is augmented by realistic errors is available for the gravity field retrieval process. Several features of this new dataset will be highlighted in this presentation in order to provide guidance for its application in upcoming future mission simulation studies.