Modelling time variations of global gravity field by the finite element method

In our research, we propose a novel numerical approach based on the finite element method applied for modelling time variations of global Earth’s gravity field in the space domain. As input data we use the GRACE-FO satellite gravity data which are prolonged and filtered on the Earth's surface, while the Earth's surface is determined by digital elevation model on lands and mean sea surface obtained by satellite altimetry. Then the surface gravity disturbances on the Earth's surface serve as the boundary condition for the geodetic boundary value problem. Away from the Earth we involve the so-called mapped infinite elements which naturally prescribe the regularity of the disturbing potential at infinity. Afterwards, the obtained solution is determined at every moment when new input data is applied. In this way, we dynamically determine the Earth's gravity field on and above the Earth's topography.