An Innovative Slepian Approach to Invert GRACE KBRR for Localized Hydrological Information at the Sub-Basin Scale

GRACE spherical harmonics are well-adapted for representation of hydrological signals in river drainage basins large size such as the Amazon or Mississippi basins. However, when one needs to study smaller basins, comes up against low spatial resolution solutions harmonics. To overcome this limitation, we propose a new approach based on Slepian functions which can reduce energy loss by integrating information spatial, spectral and time domains. Another advantage these regionally-defined is reduction problem dimensions compared harmonic parameters. This also induces drastic computational time. These used invert satellite data restore water mass fluxes different hydro-climatologic environments Africa. We apply them two African chosen their medium scale geometric specificities: Congo basin with quasi-isotropic shape Nile an anisotropic more complex shape. Time series coefficients have been estimated from real along-track geopotential differences about ten years, agreement both provided official centers CSR, GFZ, JPL GLDAS model validation. The function analysis highlights variations at sub-basin scales