Terrestrial Water Storage Anomalies
Globally gridded estimates of terrestrial water storage anomalies have been derived, and used to calculate area-average time series for 100 drainage basins worldwide. Since mass variations are inferred from observed orbit perturbations at satellite altitude, where the effects of very local mass anomalies are substantially diminished, only the large-scale features of water storage redistributions are reliably captured. Therefore, the accuracy of the GRACE mass change estimates increases with increasing basin area. Typically, the accuracy for river basins with areas of a few 100,000 km² is less than a few cm equivalent water height.
To down-scale GRACE information to more regional estimates, re-scaling factors based on a small ensemble of global numerical land surface schemes and hydrological models are available. However, we do not recommend a direct comparison of the re-scaled GRACE products at the 1° resolution to independent estimates or to model results, but recommend averaging over sub-basins of at least 100,000 km².
Further processing details are available in the following paper:
Zhang, L., Dobslaw, H., Thomas, M., 2016:
Globally gridded terrestrial water storage variations from GRACE satellite gravimetry for hydrometeorological applications
Geophysical Journal International, 206, 1, p. 368—378 , http://doi.org/10.1093/gji/ggw153