Multi-year regional water mass solutions by inversion of hydrology-related GRACE(-FO) KBRR residuals

Our analysis presents 10-day water mass solutions estimated from both GRACE and GRACE-FO KBR Range (KBRR) residuals for continental hydrology using GINS software developed by the CNES/GRGS group.  The inter-satellite velocity residuals have been converted into along-track differences of gravity potential using the energy balance approach. Maps of Equivalent Water Height (EWH) are obtained by inversion of these potential differences onto juxtaposed surface elements over the region of interest or time coefficients of designed orthogonal Slepian functions. This latter band-limited representation offers the advantage of reducing  drastically the number of parameters to be fitted and the computation time. We also used another type of orthogonal basis functions, as well as decomposition using anisotropic wavelets. These functions require larger computing resources but have the advantage of being adapted to the shape of the studied watersheds for improving hydrology variation survey locally. All of these regional solutions are compared to spherical harmonics and mascons series of existing Level-2 solutions for validation. The patterns shown in the proposed regional solutions reveal dominant seasonal cycles of water mass in the large tropical basins (e.g. Amazon,  Nil and Congo), as well as extreme events such as floods and droughts.