Mass displacements and motions inside and between individual components of the Earth system reflect dynamic processes which affect the rotation as well as the gravity field and the shape of the Earth.
The integral mass variations monitored by the satellite gravity mission GRACE contain amongst others atmospheric, oceanic and hydrological mass displacements. To identify mass transports within the Earth system it is necessary to separate the individual components. Like suggested in the illustration below geophysical models of the system components (e.g. WGHM in the case of continental hydrology) can be chosen to deduce adequate mathematical systems of functions. If the same method is applied to all accountable system components (hydrology, ocean and atmosphere) a total model for the gravitational potential is derived by combining the individual model approaches. This model consists of different systems of base functions for the spatial representation and unknown series coefficients reflecting the temporal evolution of the components. Since the GRACE system measures potential differences the unknown series coefficients can be calculated by parameter estimation. If they are estimated enhanced geophysical models exist (see illustration 2). These can be valuated by independent data like GPS time series or time series of supra-conduction gravimeter.
