Regionally Refined Gravity Field Models from In-Situ Satellite Data

The satellite mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) will enable the determination of the Earth’s gravity field with unprecedented accuracy, especially regarding the high-frequency part of the gravity field spectrum. To exploit the full potential of the mission, it is advantageous to develop methods to extract as much information out of the given signal as possible. In the approach presented here a global gravity field represented by a spherical harmonic expansion up to a moderate degree is derived in a first step and then refined by regionally adapted high resolution refinements being parameterized by splines as space localizing basis functions. These radial basis functions are designed to reflect the spectral characteristics of the gravity field to be modeled. Another important aspect in the regional gravity field analysis approach is the downward continuation process. In this context, a regionally adapted regularization will be introduced, which assigns different regularization matrices to geographical areas with varying signal content. Regularization parameters individually determined for each region take into account the varying frequency behavior, allowing to extract additional information out of a given data set. If desired, regional solutions with global coverage can be combined to a global solution using quadrature methods. The approach is demonstrated by a simulation scenario that combines a global GRACE solution as reference field with regional refinements calculated from GOCE observations.