Estimating terrestrial water storage trends by developing a joint inversion scheme using GRACE and GRACE-FO data

Climate change and global warming can affect the water cycle, leading to increased hydrological extremes, such as droughts affecting the environment, agricultural activities, and human life and causing serious social and economic problems worldwide. Therefore, monitoring changes in the water cycle can be helpful for effective water resources management and provide a management plan for sharing with stakeholders, water managers, and local people. This study focuses on terrestrial water storage changes (e.g., trends and seasonal shifts) that potentially indicate climate change patterns like droughts and large scale flooding events within watersheds across the Horn of Africa. In this study, an inversion scheme is being developed to process level-2 data obtained from the Gravity Recovery and Climate Experiment (GRACE) and subsequent measurements from GRACE Follow-On (GRACE-FO) spanning the period from 2002 to 2023 considering the variance-covariance matrix (error matrix) of observations for estimating TWS variations monthly at basin scale. We expect that our inversion scheme will be independent of filters, and there will be no need for empirical rescaling factors to amplify the primary signal after filtering and damping effect. The TWS changes estimated from the developed inversion scheme will be compared with the TWS trends of basins that have been derived using the basin averaging standard approach and Mascon solutions TWS changes products. Additionally, the atmospheric reanalysis products will be used, along with hydrological model discharge estimates, to assess the accuracy of time derivatives of TWS changes.