Towards the Separation of Integral GRACE Signals of Continental Water Storage Using Multi-Sensor Space and In-situ Observations

The latest IPCC assessment report identified once more the land hydrology as the most uncertain component of the global water cycle. Variations of continental water storage occur in several hydrological compartments such as groundwater, soil moisture, surface water and snow. These storage variations and related changes of mass and surface water extensions map into a considerable number of different space based or in-situ observation systems such as the GRACE gravity field mission, radar and laser altimeter systems, radiometers, optical sensors, synthetic aperture radar, and in-situ river gauges. We perform a multi-sensor approach in order to detect, separate and balance individual contributions to continental water storage variations for selected large river basins. A specific focus is placed on the analysis of climate signals. The study exploits the synergies of various observation systems and combines their output with hydrological simulation models. Thus, the project provides significant new and valuable insights into hydrological processes and the impacts of climate change on the global water cycle. The roadmap includes (1) the elaboration of the potential und usability of contemporary space-borne and terrestrial sensors, (2) a quantification of water storage variations in different compartments from multi-mission analysis, (3) an assessment of the total water storage change from GRACE gravimetry, (4) the computation of the water balance for different study areas, (5) the analysis of balance inconsistencies with respect to non-hydrological mass changes, and (6) the interpretation of the results for water storage changes in terms of variability of weather and climate.