A global analysis of temporal and spatial variations in continental water storage

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Abstract
While continental water storage plays a key role in the Earth's water, energy, and biogeochemical cycles, its temporal and spatial variations are poorly known, in particular, for large areas. This study analyzes water storage simulated with the Watergap Global Hydrology Model. The model represents four major storage compartments: surface water, snow, soil, and groundwater. Water storage variations are analyzed for the period 1961–1995 with 0.5° resolution, for the major global climate zones, and for the 30 largest river basins worldwide. Seasonal variations are the dominant storage change signal with maximum values in the marginal tropics and in snow‐dominated high‐latitude areas. Interannual variations are associated with large‐scale oscillations such as El Niño Southern Oscillation. The contribution of individual water storage compartments to total storage change varies with the climate region and the timescale under consideration. In most regions, a prominent role of storage variations in surface water bodies is found. Surface water reduces markedly the spatial correlation lengths of water storage fields. The simulation results are evaluated against storage variations of combined atmospheric‐terrestrial water balance studies and other global models. This study contributes to an improved understanding of continental water storage for which the consistent integration of model results and new observations such as from time‐variable gravity data of the Gravity Recovery and Climate Experiment (GRACE) satellite mission is required.