Spatiotemporal variability of terrestrial water storage over the Tibetan Plateau from the joint inversion of GNSS and...

The Tibetan Plateau (TP), characterized by its unique regional features and geographical landscape, is a critical area for studying changes in terrestrial water storage (TWS), which are significantly influenced by global warming. In this study, we integrate data from the Global Navigation Satellite System (GNSS) and the Gravity Recovery and Climate Experiment (GRACE) to jointly estimate TWS variations in the TP and examine their spatiotemporal fluctuations in relation to large-scale climate patterns. To evaluate our approach, we conducted two synthetic tests, which showed that the root mean square errors (RMSEs) for the joint inversion were 23-37% lower than those for GNSS inversion, confirming the effectiveness of our method. When applied to real observational data, the joint inversion technique revealed that the spatial patterns and seasonal characteristics of TWS changes closely aligned with independent GRACE and Global Land Data Assimilation System (GLDAS) products, while offering more detailed insights into local hydrological processes. Notably, during the 2015/2016 El Niño event, the central and eastern TP experienced severe drought, primarily driven by precipitation anomalies (~ -150 mm) associated with extreme climate events, leading to a delayed hydrological response to the meteorological drought. Furthermore, we observed significant interannual variability across the TP sub-basins, with a moderate correlation with the El Niño/Southern Oscillation (ENSO) at a one-month lag. Our research highlights the potential of joint inversion using GNSS and GRACE to enhance TWS monitoring in the TP, providing more spatially detailed insights into water storage variability in response to climate change.