Overview of GMAO met data products

GMAO met field comparison chart

	GEOS-1	GEOS-STRAT	GEOS-3	GEOS-4	GEOS-5	MERRA
Native # of levels	20 sigma	26 sigma	48 sigma	55 hybrid	72 hybrid	72 hybrid
Native grid	2° x 2.5°	2 x 2.5	1° x 1°	1° x 1.25°	0.5° x 0.666°	0.5 x 0.666 and 1 x 1.25
Native file format	Binary	Binary	HDF4-EOS	HDF4-EOS	HDF4-EOS	HDF4-EOS
Regridded to	2° x 2.5° 4 x 5	2° x 2.5° 4° x 5°	1° x 1° nested °2 x 2.5° 4° x 5&degl	2° x 2.5° 4° x 5°	0.5° x 0.666° nested 2° x 2.5° 4° x 5°	4 x 5
Temporal coverage	1985 - 1995	1996 - 1998	2000 - 2002	1985 - 2007	2004 - present	1979 - 2010

NOTES:

1. GEOS-1 and GEOS-STRAT are now obsolete and no longer supported by GEOS-Chem
2. GEOS-3 is still supported but we recommend users to migrate to GEOS-4 or GEOS-5.
3. MERRA data will be made available at 4 x 5 resolution in the near future. MERRA is a long-term reanalysis done with version GEOS-5.2.0.

--Bob Y. 16:24, 27 July 2010 (EDT)

GEOS-5 and MERRA

Text to be added

GEOS-4

References

1. Documents which describe the validation of GEOS-4 met fields in GEOS-Chem
2. Technical References

GEOS-3

GEOS-3 was an improvement over GEOS-1 and GEOS-STRAT. However, because GEOS-3 was a pure-sigma model, there were problems in the stratosphere caused by excess noise in the winds. The GEOS-3 product was extensively used in GEOS-Chem for TRACE-P mission analysis.

Assimilation GCM used:	NASA/GSFC GEOS–3 GCM
Native horizontal grid:	1° x 1°
Native vertical grid:	48 sigma levels; model top at 0.01 hPa
Native file format:	HDF4-EOS
Temporal coverage:	2000-2002
We regridded to:	1° x 1° nested grids, 2° x 2.5°, 4° x 5° at 48 sigma layers
Strengths:	High resolution made 1° x 1deg; nested sims possible Higher model top
Weaknesses:	P to sigma vertical interpolation had to be done STE still not realistic U, V winds were very noisy at the top of the atmosphere

GEOS-1 and GEOS-STRAT

GEOS-1 was the first GMAO met field data product compatible with GEOS-Chem. GEOS-STRAT was a continuation of GEOS-1, but with a finer vertical grid. Both products have been superceded by newer versions of GMAO met products and are no longer supported in GEOS-Chem.

GEOS-1 features

Assimilation GCM used:	NASA/GSFC GEOS1 GCM
Native horizontal grid:	2° x 2.5°
Native vertical grid:	20 pure-sigma layers, model top at 10 hPa
Native file format:	NASA PHOENIX format (binary Fortran unformatted)
Temporal coverage:	1985-1995
We regridded to:	4 x 5; 20 pure-sigma layers
Strengths:	Long temporal coverage (10 years)
Weaknesses:	Very low model top (10 hPa) Strat-trop exchange was too fast by 2-3X

GEOS-STRAT features

Assimilation GCM used:	NASA/GSFC GEOS1 GCM
Native horizontal grid:	2° x 2.5°
Native vertical grid:	46 pure-sigma layers, model top at 0.1 hPa
Native file format:	NASA PHOENIX format (binary Fortran unformatted)
Temporal coverage:	1996-1997 (some 1998)
We regridded to:	4 x 5; 26 pure-sigma layers
Strengths:	Higher model top, better stratospheric representation
Weaknesses:	Vertical grid did not correspond to GEOS–1 STE still too fast by 2-3X Surface data had a 6-hr temporal resolution, we had to interpolate to a 3-hr temporal resolution ourselves

--Bob Y. 16:43, 27 July 2010 (EDT)