GRACE/GRACE-FO HAM is derived from terrestrial water mass changes (TWS) from the two monthly GravIS Level-3 products GFZ and COST-G. These products are derived from time-variable satellite gravity fields representing integrated terrestrial mass redistribution at monthly time steps and an effective spatial resolution of 1°. HAM is calculated directly from the continental mass-anomaly fields. Because GRACE/GRACE-FO does not observe horizontal water transport, no corresponding motion term is derived. The GFZ product is based on GFZ RL06 GRACE/GRACE-
FO spherical-harmonic gravity-field solutions, whereas the COST-G solution is based on the corresponding combination solutions produced by the Combination Service for Time-variable Gravity Fields (COST-G). The Level-2 gravity solutions are post-processed to replace poorly determined low-degree coefficients, account for geocenter motion and GIA, and suppress correlated errors using anisotropic VDK filtering before synthesis into Level-3 mass grids. The operational GravIS Level-3 processing combines differently filtered solutions: deterministic components including trend, annual, and semiannual variations are treated separately from the residual variability.

All available GRACE GravIS - GFZ TWS HAM can be downloaded here.

All available GRACE GravIS - COST-G TWS HAM can be downloaded here.