GNSS2TWS_Slepian: A software to recover GNSS-inverted terrestrial water storage changes based on Slepian basis functions

Changes in terrestrial water storage (TWS) can deform the Earth’s solid surface, resulting in geodetically measurable vertical displacements. Here, a new open-source Matlab software, called GNSS2TWS_Slepian, has been developed to recover daily TWS changes using Global Navigation Satellite System (GNSS) observed vertical crustal positions. Unlike traditional spatial-domain inversion strategy based on Green's function method, our inversion modeling is implemented in the spectral domain based on Slepian basis functions. This approach enables the estimation of large-scale TWS changes from non-uniformly distributed GNSS vertical data. GNSS2TWS_Slepian is designed with different structured modules, making the program logic easy to follow. To obtain daily estimates of TWS changes, the principal component analysis is integrated into our time-varying inversion model. To demonstrate its core capabilities and hydrological applications, daily equivalent water height changes are estimated and hydrological extremes are characterized in the Western United States. This study aims to provide a scientific mathematical tool for resolving large-scale water mass loads, expanding the potential applications of GNSS technology in hydrology.