The image is an illustration of the twin GRACE satellites orbiting the Earth at an altitude of approximately 490 km. The distance between the two satellites is 220 km and they orbit the Earth in about 95 minutes. The potato shaped image of the Earth known as the “Potsdam gravity potato” shows the difference in the strength of the gravity field across the planet, where higher (red) areas represent stronger gravity and lower (blue) areas weaker gravity.
GRACE IN A NUTSHELL
The Gravity Recovery and Climate Experiment (GRACE 2002-2017) as well as its Follow-On (GRACE-FO 2018-onwards), are joint satellite missions between the National Aeronautic and Space Administration (NASA-JPL), the German Aerospace Center (DLR) and the German Research Centre for Geosciences (GFZ) in Potsdam.
GRACE data provides unique information to monitor areas where little or no in-situ hydrological data is available and where models fail in recovering the water storage changes. It is shown in different studies that GRACE is able to catch seasonal changes as well as large decadal declining and rising water storage trends connected to climate and human-induced trends, that are underestimated and not realistically represented by the global hydrological and meteorological models. GRACE data today, as a stand-alone solution, is valid for large areas. However, combined with local and regional hydrological data, the spatial resolution of GRACE data may actually be a benefit when quantifying changes in total terrestrial water storage (TWS) at regional scales. GRACE data are considered to provide the “big picture” in terms of global water storage. By integrating all water storage components (including groundwater), TWS can be used to quantify and predict water availability, which is critical for water resources management, e.g. when predicting the impact of floods and droughts.