Monthly mean of background models
=================================

The ITSG-Grace2018 signal definition is consistent with the official SDS solutions. During the 
gravity field recovery process, the following background models are reduced from the data:
  - ocean tide: FES2014b, co-estimated
  - pole tide: IERS 2010
  - ocean pole tide: Desai 2004 (IERS 2010)
  - atmospheric tides: AOD1B RL06
  - atmosphere and ocean dealiasing: AOD1B RL06
  - sub-monthly continental hydrology: LSDM
  - relativistic corrections: IERS 2010

These effects are not present in the monthly solutions. We provide monthly means of these models
in the folder "monthly_background" so that the full tidal/non-tidal gravity can be restored.

Additionally, we provide monthly means of geophysical to provide signal separation in
the folder "monthly_signalSeparation". These can be used to reduce further effects such as
glacial isostatic adjustment. The models available are:

 - Glacial Isostatic Adjustment (GIA, Steffen 2017)
 - Atmosphere (AOD1B RL06)
 - Ocean (AOD1B RL06)
 - Ocean bottom pressure (AOD1B RL06)
 - Hydrology (LSDM)


References
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Dobslaw, H., Bergmann-Wolf, I., Dill, R., Poropat, L., Thomas, M., Dahle, C., Esselborn, S., König, R., Flechtner, F.: A New High-Resolution Model of Non-Tidal Atmosphere and Ocean Mass Variability for De-Aliasing of Satellite Gravity Observations: AOD1B RL06. Geophysical Journal International, 211(1), 263-269, DOI: doi.org/10.1093/gji/ggx302.
Dill, R. (2008): Hydrological model LSDM for operational Earth rotation and gravity field variations. GFZ ScientificTechnical Report STR08/09.
Cheng, M., J. C. Ries, and B. D. Tapley (2011), Variations of the Earth's figure axis from satellite laser ranging and GRACE, J. Geophys. Res., 116, B01409, doi:10.1029/2010JB000850.
Cheng, M.K., B.D. Tapley, J.C. Ries (2010) Geocenter Variations from Analysis of SLR data, IAG Commission 1 Symposium 2010, Reference Frames for Applications in Geosciences (REFAG2010), Marne-La-Vallee, France, 4-8 October 2010.