Monitoring the spatiotemporal response of terrestrial water storage using gravity and deformation: Current status and prospects for data, methods, models, technologies and applications

As the main carrier of mass migration, exchange and circulation in the Earth's hydrosphere cycle processes, the redistribution of land water plays a vital role in climate change and human activities. The time-varying (or time-lapse) 4D surface and satellite gravity, and deformation observations have had a revolutionary impact on the study of spatiotemporal changes in terrestrial water storage (TWS), but they still face challenges in terms of resolution and sensitivity of hydrological signal monitoring. This study introduces the scientific background and main geophysical observation methods for studying TWS changes. Focusing on gravity and deformation monitoring of global/regional spatiotemporal responses of hydrological mass signals as the goal, we sequentially expound on the basic principles, data models, processing techniques, inversion methods and driving factors involved in recent years. Based on application examples, the basic ideas and processes of estimating TWS using surface gravity (continuous and absolute), satellite gravity (GRACE) and GNSS observations are given in detail, and then the problems and technical bottlenecks that may exist in gravity and deformation solutions so far are discussed. Finally, we briefly look forward to the application prospects of monitoring water mass migration and the underlying causes based on gravity and deformation technology. This study provides a variety of perspectives for in-depth understanding of the TWS changes and its driving factors, and has reference value for the development of Hydrogeophysics.