JPL GRACE and GRACE-FO Mascon RL06 Processing Chain

The JPL GRACE and GRACE-FO Mascon RL06 Processing Chain is operated by JPL (Jet Propulsion Laboratory, NASA) and distributed via PO.DAAC.^[1] It processes Level-1B inter-satellite K-band ranging measurements from GRACE (2002-2017) and GRACE-FO (2018-present) into monthly gridded terrestrial water storage anomalies.

The algorithm solves a least-squares inversion for 4,551 equal-area 3-degree spherical cap mascons distributed across the Earth's surface.^[2] Explicit spatial and temporal regularization constraints reduce noise at the Level-2 processing step, in contrast to the post-hoc empirical filtering applied to spherical harmonic solutions. An optional Coastal Resolution Improvement (CRI) filter is available to reduce signal leakage at land-ocean boundaries in coastal mascon cells.^[3]

Outputs are monthly global terrestrial water storage (TWS) anomalies expressed as Equivalent Water Height (EWH, centimetres) on a 0.5-degree latitude/longitude grid (720x360 cells), together with gain factors for hydrology signal recovery.^[4] Release history: RL05M (first mascon release), RL06M v01, RL06M v02 (2019), RL06.1Mv03, and the current release RL06.3Mv04 (2024, DOI 10.5067/TEMSC-3MJC6).^[1]