Evaluating the weekly changes in terrestrial water storage estimated by two different inversion strategies in the Amazon River Basin

Abstract

In this study, we estimated the weekly Gravity Recovery and Climate Experiment (GRACE) spherical harmonic (SH) solutions and regional mascon solutions using GRACE-based Geopotential Difference (GPD) data and investigated their abilities in retrieving terrestrial water storage (TWS) changes over the Amazon River Basin (ARB) from January 2003 to February 2013. The performance of the weekly GPD-SH and GPD-mascon solutions was evaluated by comparing them with the weekly GFZ-SH solutions, Global Land Data Assimilation Systems (GLDAS)-NOAH hydrological model outputs, and monthly GFZ-SH, GPD-SH, and CSR-mascon solutions in the spatio-temporal and spectral domains. The results demonstrate that the weekly GPD-SH and GPD-mascon present good consistency with the weekly GFZ-SH solutions and GLDAS-NOAH estimates in the spatio-temporal domains, but GPD-mascon presents stronger signal amplitudes and more spatial details. The comparison of the monthly average of weekly estimates and monthly solutions demonstrates that the weekly GPD-mascon and GFZ-SH with DDK1 filtering are close to the monthly CSR-mascon and GFZ-SH solutions, respectively. However, the signal amplitudes of TWS changes from GPD-SH and GFZ-SH with 650 km Gaussian filtering are smaller than the monthly solutions, and the corresponding Root Mean Square Errors between the TWS change time series from the monthly average of weekly solutions and monthly estimates are 18.12 mm (GPD-mascon), 18.81 mm (GFZ-SH-DDK1), 24.93 mm (GPD-SH-G650km), and 33.07 mm (GFZ-SH-G650km), respectively. Additionally, the TWS change time series derived from weekly solutions present more high-frequency time-varying information than monthly solutions. Furthermore, the 300 km Gaussian filtering can improve the signal amplitudes of TWS changes from the weekly GPD-SH solutions more than those with 650 km Gaussian filtering, but the corresponding noise level is higher. The weekly GPD-SH and GPD-mascon solutions can extend the application scopes of GRACE and provide good complements to the current GRACE monthly solutions.