Estimating Terrestrial Water Storage Changes over the Tibetan Plateau from GRACE/GRACE-FO Monthly Solutions Using a Variable-shaped Mascon Method: Processing Workflow and Preliminary Analysis

GRACE/GRACE-FO data are commonly provided in the form of spherical harmonic solutions (SHCs) or mass concentration (mascon) solutions. Compared with SHCs, mascon solutions usually require simpler post-processing, exhibit higher signal-to-noise ratios, suffer less from leakage errors, and provide improved effective spatial representation; therefore, they are widely used in interdisciplinary studies such as hydrology and glaciology.
The mascon method approximates continuous surface mass changes by representing them as a series of discrete units with internally homogeneous mass, based on locally defined basis functions. Consequently, the size, shape, and positioning of these mascons have a significant impact on solution accuracy. In certain regions characterized by strong spatiotemporal heterogeneity of surface mass changes, such as the North China Plain, the Tibetan Plateau, and Greenland, differences among mascon solutions largely arise from variations in their parameterization and regularization strategies.
In this study, we use the unconstrained ITSG-Grace2018/ITSG-Grace operational monthly SHCs covering the period from April 2002 to December 2022, with a maximum degree and order of 96, incorporating the full noise covariance matrices. Based on the open-source ANGELS-Mascon software, variable-shaped mascons are customized, and weighted least-squares inversions with generalized Tikhonov regularization are performed over the Tibetan Plateau. By constructing various combinations of parameterization and regularization, we are comparing the performance of different mascon solutions in signal extraction, noise suppression, and spatial representation, with the aim of identifying a statistically optimal solution for the Tibetan Plateau.
This contribution mainly presents the processing workflow and preliminary analyses. A systematic comparison of different configurations is ongoing, and further analytical findings will be presented at the conference.