Evaluation of the OMP 2025 AOD1B dealiasing product based on the TUGO ocean dynamics numerical model

Abstract

Temporal aliasing of sub-monthly gravimetric signals originating from the Earth's fluid envelope is a major source of error in time-variable gravity field models derived from the GRACE and GRACE Follow-On missions. Minimizing these errors to detect gravimetric signals providing information on solid Earth dynamics and the climate system remains a major challenge.The GET and LEGOS laboratories in Toulouse have calculated the atmospheric and oceanic contributions to the time-variable gravity field, compiled into the OMP 2025 AOD1B dealiasing products, for the future processing of GRACE and GRACE-FO data.These products rely on an updated and improved version of the TUGO ocean dynamics numerical model and the ECMWF ERA5 3D atmosphere model. These atmospheric and oceanic dealiasing products (OMP 2025) include: (1) time-variable atmospheric gravitational potential anomalies generated from ECMWF ERA5 model levels (including hydrometeors, i.e., specific water content of rain, snow, cloud liquid, and ice), realistically distributed according to altitude above the geoid; and (2) time-variable oceanic gravitational potential anomalies calculated from ocean tides forced by ERA5 ocean surface fields (pressure and wind), with these water height anomalies realistically placed on the geoid. The oceanic response to atmospheric forcing is derived from the TUGO hydrodynamic model without assimilation and the FES2022 ocean tide model (validated by altimetry tides).These new dealiasing products are compared, after GRACE/GRACE-FO data reduction, meaning at the gravity field solution level, with the GFZ AOD1B RL06 and RL07 products officially used in GRACE/GRACE-FO processing. To this end, monthly GRACE gravity field solutions were calculated for 2006 and 2020 using these different dealiasing products, and the resulting monthly solutions are compared to analyze their differences. The analysis of post-fit residual differences between different dealiasing gravitational potential models, as well as the RMS of quiet zones and differences in monthly GRACE/-FO variable field solutions, will be presented.Additionally, the new GFZ MIXED2025 ocean tide model is compared to the LEGOS FES2022 model at the gravity field solution level.