COM-TG: Combined Mascon Solution
COM-TG is a temporal gravity field mascon product derived from four GRACE and GRACE-FO solutions: GSFC, CSR, ANU, and JPL. It combines the large-scale accuracy of JPL with the finer spatial detail of the smaller-scale mascon products.

What are mascons?

Mass concentration elements (mascons) are "tiles" used to cover the surface of the Earth on which changes in mass are estimated using data from the GRACE and GRACE Follow-On satellite missions. There are a number of different mascon solutions available globally, all of which have been produced making different assumptions:

  • The size and shape of the mascons used
  • Defining which mascons are land and which are ocean
  • How floating ice shelves are handled in polar regions
  • Strategies for adding numerical stability to the data inversions

Consequently, combining mascon solutions turns out to be a rather complex process, but it is possible!

 

Why a combined mascon solution?

The COM-TG combined mascon solution exploits the benefits of the larger, less correlated mascons of the JPL solution with the higher spatial resolution of the ANU, CSR and GSFC mascon solutions. The resulting product, evaluated on ~100 km mascons, provides estimates of the temporal gravity field that has a RMSE of 3-5 cm with respect to each of the input mascon solutions and produces the expected spatial patterns while removing certain anomalies/idiosyncrasies of each of the solutions. The COM-TG solution suppresses noise relative to individual input mascon products and preserves large-scale patterns while maintaining meaningful spatial variability. 

The land/ocean coastline boundaries were unified across the input mascon solutions then the Coastline Resolution Improvement (CRI) filter of Wiese et al. (2016) was applied to resolve smearing of signals across coastline boundaries. We assess the sensitivity of the COM-TG solution to the weighting of the input mascon solutions and demonstrate that the results are relatively insensitive to the choice of observation weights.

We also provide a 0.25o global land-ocean-grounded ice mask to facilitate more straightforward combination of future mascon solutions if adopted by the GRACE processing community.  
 

Publication 

Please cite the following if using the COM-TG mascon solution:

McGirr, R. and P. Tregoning, A combined mascon product from multiple analyses of GRACE and GRACE Follow-On space gravity data, Geophysical Research Letters, submitted May 2026.

 

Fused mascon solution mean (2003-2023)
Fused mascon solution mean (2003-2023) at 1-degree spatial resolution

 

Files

COM-TG mascon solution

The COM-TG combined mascon solution is provided in netcdf format on a 0.25o global grid ( COM-TG_200204-202511_all-corrections.nc ). This file also includes the coastline mask (on a 0.25o grid) used to unify the input mascon solutions.