Reconstruction of climate-driven global terrestrial water storage variations (2002–2021) using a four-parameter linear recursive model

Abstract. Terrestrial water storage anomalies (TWSA), jointly influenced by climatic variability and human activities, exhibits pronounced fluctuations across multiple temporal scales. A substantial portion of the fluctuations is attributed to climatic variability, like the El Niño–Southern Oscillation (ENSO). Empirical reconstruction of climate-driven water storage based on relationships between GRACE satellite gravity observations and meteorological forcing data has become a common approach; however, existing models often neglect the regulating role of temperature in the transformation of precipitation into water storage. In this study, we propose a linear, four-parameter coupled recursive model that explicitly incorporates temperature effects on both the conversion and dissipation efficiency of water storage. Using GRACE/GRACE-FO satellite observations and meteorological forcing data, we reconstructed climate-driven TWSA over the global land grid (excluding Antarctica) at a monthly temporal resolution and 0.5° spatial resolution for the period 2002 to 2021. For 116 major global river basins, we further derived basin-scale TWSA reconstructions and quantitatively evaluated the fraction of precipitation converted into TWSA. Compared with existing statistical reconstruction products, the results indicate that: (1) the proposed method achieves substantially faster parameter convergence, improving computational efficiency by several tens of times during the TWSA reconstruction process; (2) the proposed model demonstrates superior performance in approximately 89 % of river basins and 62 % of global land grid cells. Additional comparisons with the physically based Catchment Land Surface Model (CLSM) product from NASA's Global Land Data Assimilation System (GLDAS) show that the proposed method better captures the temporal variability of GRACE TWSA in most basins. At the daily scale, the reconstructed TWSA agrees well overall with the ITSG-Grace2018 daily solution and GLDAS-2.2. This study enhances the understanding of the mechanisms governing terrestrial water storage variations at both global and regional scales, provides a quantitative assessment of climate-driven water storage changes, and offers a solid foundation for disentangling the respective impacts of climatic variability and human activities on water resources.