Spatial distribution characteristics and mechanism of nonhydrological time-variable gravity in mainland China

The purpose of this study is to explore nonhydrological mass transfer in mainland China. For this purpose, obtained the spatial distribution of time variant gravity signals in mainland China using gravity recovery and climate experiment (GRACE) data. Then, according to the current hydrological model and other auxiliary hydrological data, a new combined hydrological model of mainland China was constructed. Finally, the time variant signals of the above combined hydrological model were deducted from the time variant gravity field of GRACE to obtain the nonhydrological mass transfer of mainland China, and its physical sources and mechanisms were discussed. In this study, according to the existing hydrological models, the hydrological components with the best correlation were selected through correlation calculation, analysis, and comparison, and a more reasonable combined hydrological model was created. This combined hydrological model includes soil water, snow water, vegetation canopy water, groundwater, lakes, glaciers, and other water components (mainly reservoir storage, swamps, rivers). The spatial distribution of the nonhydrological mass transfer signals in mainland China was obtained by deducting the combined hydrological model from the GRACE time-variable gravity field. The results show that the nonhydrological signals in mainland China were mainly positive signals, which were distributed in the Bohai Rim and the northern and eastern parts of the Tibetan Plateau. The above nonhydrological mass transfer signals were further studied and discussed. The results show that the nonhydrological mass migration signals in the Bohai Rim region primarily originate from sea-level change and marine sediment accumulation. The mass accumulation of Indian plate collision in the Tibetan Plateau was the main reason for the increase in the residual gravity field in the Tibetan Plateau.