Triangular grids on the sphere

Inverting LRI data from GRACE-FO (NASA/GFZ) is challenging from  multiple points of view. To benefit from the laser instrument, that provides a higher precision compared with the KBR ranging, the global basis functions such as spherical harmonics may not provide the best service for exploiting data the full potential. Because the regional analyses use surface elements such as mascons, we present two alternatives in terms of the spherical triangles that may also be used as target elements for the inversion. Since the spherical trigonometry can be used, a relatively easy manipulation and remeshing is possible if appropriate indexing is used. Furthermore, such grids are also used in the solid-Earth models models like LITHO1.0 and WINTER-C, and, thus they may provide an easy link from satellite gravimetry to solid-Earth disciplines. We show the properties of both grids, how to properly index them and how to reduce SST data for the continental part of the signal with the monthly solutions.