3D high-resolution numerical modelling of altimetry-derived marine gravity data using FEM

We present 3D numerical modelling of the altimetry-derived marine gravity data with the high horizontal resolution 1 x 1 arc min. The finite volume method (FVM) as a numerical method is used to solve the altimetry-gravimetry boundary-value problem. Large-scale parallel computations result in disturbing potential in every finite volume of the discretized 3D computational domain between an ellipsoidal approximation of the Earth’s surface and upper boundary chosen at altitude of 200 km. Afterwards, the first, second or third derivatives of the disturbing potential in different directions are numerically derived using the finite differences. A process of preparing the Dirichlet boundary conditions over ocean/seas has a crucial impact on achieved accuracy. It is based on nonlinear filtering of the geopotential generated on a mean sea surface (MSS) from a GRACE/GOCE-based satellite-only global geopotential model.

   We present different types of the altimetry-derived marine gravity data obtained on the DTU21_MSS as well as at higher altitudes of the 3D computational domain. The altimetry-derived gravity disturbances on the DTU21_MSS are tested by shipborne gravimetry and compared with those from the recent datasets like DTU21_GRAV or SS_v31.1. The obtained altimetry-derived gravity disturbances at higher altitudes are compared with airborne gravity data from the GRAV-D campaign in US. The gravity disturbing gradients as the second derivates or the third derivatives are provided with the same high resolution on the DTU21_MSS as well as at different altitudes.