Local gravity field modeling using gravity difference observations along the line of sight of the GRACE-FO satellites and adjusted spherical cap harmonic basis functions

In this study, a regional model for the Earth's gravity field across Antarctica is presented. So, observations of gravity difference along the line of sight of the satellite (LGD), obtained from the GRACE-FO mission, are used, and the local gravity model is calculated based on the Adjusted Spherical Cap Harmonics (ASCH) basis functions. in this method, by introducing a scale factor and applying a mapping to the domain and boundary of the problem, we can use legendre functions of the integer degree and order (similar to global harmonics). According to the characteristics of basic functions, first, a new method for converting LGD data to the ASCH domain and calculating harmonic coefficients is provided. In order to reduce the edge error effect, the gravity grid data beyond the boundary of the studied area is generated using a geopotential model. To verify the validity of the study, a set of control points are selected from the LGD data and in the path of the profiles (orbital paths of the GRACE satellite over the studied area) to verify the accuracy of the local model. Therefore, when the results of the local model are compared with the control points, the root mean square error is equal to 0.9 (nm/s2). which is comparable to the accuracy of LGD data of 0.15 nm/s2. On the other hand, the root mean square error of global geopotential models against LGD data is equal to 6 nm/s2. Because of this, the local harmonic function (ASCH) can get more information from the gravity field and make a more accurate model of the local geopotential.