TUD-L2B-EWH_UNC: A Monthly Global Level-2B GRACE(-FO) EWH Uncertainty Product

The Gravity Recovery and Climate Experiment (GRACE) and its successor GRACE-FO provide unique observations of Earth’s time-variable gravity field, enabling direct monitoring of mass redistribution expressed as equivalent water height (EWH). While gridded Level-2B products are widely used across hydrology, glaciology, and solid-Earth studies, uncertainty information remains fragmented or inaccessible to end users. In practice, this has led to the widespread use of empirical or ad hoc uncertainty estimates, limiting data assimilation and other geophysical applications that require spatially and temporally resolved observational error information.

We present TUD-L2B-EWH_UNC-GRACE, a globally gridded Level-2B GRACE(-FO) EWH data product that provides a comprehensive and transparent characterisation of uncertainty alongside the mass anomaly fields. Unlike conventional approaches that rely on propagation of full normal matrices or impose assumptions on error correlations, TUD-L2B-EWH_UNC combines ensemble statistics from multiple independently processed Level-2 solutions to quantify pre-processing uncertainties. These include contributions from ocean tide model differences, parametrisation strategies, and uncertainty in the Atmosphere and Ocean De-aliasing (AOD1B) background model.

Post-processing uncertainties associated with filtering, leakage, and Glacial Isostatic Adjustment (GIA) are quantified separately. Filtering-related uncertainty is evaluated using a known-pair approach, while GIA uncertainty is assessed using an ensemble of 56 published GIA models. Error fields are provided for a suite of anisotropic filtering strategies (DDK(2–7)), enabling systematic assessment of filtering choices, leakage effects, and model dependence on the total uncertainty budget.

TUD-L2B-EWH_UNC is the first Level-2B EWH dataset to deliver end-to-end, spatially and temporally resolved uncertainty fields in a user-ready gridded format. This design supports consistent uncertainty handling across hydrological, glaciological, and solid-Earth applications. Ancillary tidal corrections and climatological fits of signal and leakage-related errors are distributed separately through the companion products TUD-L2B-EWH_CLIM-GRACE and TUD-L2B-EWH_CLIM_LEAKAGE-GRACE. All datasets are publicly available (DOI: doi.org/10.4121/4fc748e8-01c7-4f06-87da-653937b078f7) via the TU Delft GRACE Portal (https://grace-cube.lr.tudelft.nl/).