Overview of GMAO met data products

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On this page we shall list the features of the various meteorological data products produced by NASA's Global Modeling and Assimilation Office. These products are used to drive GEOS-Chem.

GMAO met field comparison chart

  GEOS-1 GEOS-STRAT GEOS-3 GEOS-4 GEOS-5.2.0 MERRA GEOS-FP
(formerly GEOS-5.7.2)
Native vertical grid 20 sigma 26 sigma 48 sigma 55 hybrid 72 hybrid 72 hybrid or
42 pressure 		72 hybrid
Native horizontal 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°
1.25° x 1.25°
1° x 1.25° 		0.25° x 0.3125°
Native file format Binary Binary HDF4-EOS HDF4-EOS HDF4-EOS HDF4-EOS netCDF4/HDF5
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° 		2° x 2.5°
4° x 5° 		0.5° x 0.666° nested
2° x 2.5°
4° x 5° 		4° x 5° 0.25° x 0.3125° nested
2° x 2.5°
4° x 5°
Temporal coverage 1985 - 1995 1996 - 1998 2000 - 2002 1985 - 2007 2004 - present 1979 - 2010 2011 -

NOTES:

  1. GEOS-1, GEOS-STRAT and GEOS-3 are now obsolete and are no longer supported for GEOS-Chem
  2. MERRA is a long-term reanalysis done with version GEOS-5.2.0.
  3. The new GEOS-FP data product has now replaced the interim GEOS-5.7.2 product. This data product has an increased horizontal resolution (1/4° lat x 5/16° lon).
  4. Please also see our Notes regarding GEOS vertical grids wiki page for more information about how the sigma and hybrid grids are defined.

--Bob Y. 10:28, 19 August 2013 (EDT)

GEOS-FP

GEOS-FP (aka GEOS5-FP) is the current GMAO operational data product used with GEOS-Chem.

Summary

Assimilation GCM used: GEOS Data Assimilation System (GEOS-DAS), with GEOS5-GCM version 5.11.0
Native horizontal grid: 0.25° (lat) x 0.3125° (lon)
Native vertical grid: 72 hybrid levels; model top at 0.01 hPa
Native file format: netCDF4 (based on HDF5)
Temporal coverage: 2011-
We regridded to:
  • 0.25° x 0.3125° SE Asia and North America nested grids with 72 hybrid layers
  • 2° x 2.5° with 72 hybrid layers
  • 4° x 5° with 72 hybrid layers
Strengths:
  • Ultra-high resolution will facilitate comparison to satellites
  • Detailed nested-grid simulations with GEOS-Chem are possible at 0.25&deg x 0.3125° resolution
Weaknesses:
  • Large data volume: 1 day of GEOS-FP “raw” data files for GEOS-Chem > 21 GB!

NOTES:

  1. For GEOS-Chem, we only regrid to coarser horizontal reslution. We keep the GEOS-FP vertical grid of 72 layers. GEOS-Chem has the capability to lump levels in the stratosphere to gain computational expediencey. See: 47 vertical levels.
  2. GEOS-FP was introduced in 2011 as GEOS-5.7.2, which was the version of the GEOS5-GCM used at the time. For more information on the differences between this product and the prior operational product (GEOS-5.2.0), please see: Evolution of the GEOS-5 system from GEOS-5.2.0/MERRA to GEOS-5.7.2 (aka "Fortuna").
  3. GMAO also produces a lower-resolution product called "GEOS5-FP-IT" ("forward processing, instrument teams"), which is available at 0.5° x 0.666°. However, this product is not a true operational system because it is "frozen". This means that new scientific updates are not introduced into GEOS5-FP-IT. For GEOS-Chem, we will only use the GEOS-FP product, not only because of its higher resolution, but also because we want to take advantage of any scientific updates that are made to the GEOS-DAS assimilation system.

References

  1. GEOS-FP on the GEOS-Chem wiki
  2. List of GEOS-FP met fields used by GEOS-Chem

MERRA reanalysis

MERRA is a 30-year reanalysis product done created with version 5.2.0 of the GEOS-DAS assimilation system.

Summary

Assimilation GCM used: GEOS Data Assimilation System (GEOS-DAS), with GEOS-GCM version 5.2.0
Native horizontal grid: MERRA reanalysis data: some files are 0.5° x 0.666°, others are 1° x 1.25°
Native vertical grid: 72 hybrid levels; model top at 0.01 hPa
Native file format: HDF4-EOS
Temporal coverage: 1979-2010
We regridded to:
Strengths:
  • High resolution will facilitate comparison to satellites
  • Convection, optical depth better than in GEOS–4
Weaknesses:
  • Large data volume: 1 day of MERRA “raw” data files > 2 GB!

NOTES:

  1. For GEOS-Chem, we only regrid to coarser horizontal reslution. We keep the MERRA vertical grid of 72 layers. GEOS-Chem has the capability to lump vertical vertical levels in the stratosphere] to gain computational advantage.
  2. Some MERRA data files are only available on a fixed pressure grid with 42 layers. We have regridded those fields to 72 layers for use with GEOS-Chem.

References

For more information about the MERRA reanalysis product, please see:

  1. MERRA File Specification Document (03 Aug 2012)
  2. MERRA on the GEOS-Chem wiki
  3. List of MERRA met fields used by GEOS-Chem
  4. MERRA grid structure
  5. MERRA file naming convention
  6. MERRA data file collections (aka file types)
  7. MERRA time archiving
  8. MERRA mainstream and spinup data
  9. MERRA data holdings at GSFC
  10. Glossary of variables produced by the GEOS-DAS

--Bob Y. 11:48, 19 August 2013 (EDT)

GEOS-5.2.0

GEOS-5.2.0 (which we often refer to simply as "GEOS-5") was the previous operational data set. This now has been completely replaced by GEOS-FP.

Summary

Assimilation GCM used: GEOS Data Assimilation System (GEOS-DAS), with GEOS5-GCM version 5.2.0
Native horizontal grid:

0.5° x 0.666°

Native vertical grid: 72 hybrid levels; model top at 0.01 hPa
Native file format: HDF4-EOS
Temporal coverage:
  • 2004-2012
  • Partial coverage for 2003 and 2013
We regridded to:
Strengths:
  • High resolution will facilitate comparison to satellites
  • Convection, optical depth better than in GEOS–4
Weaknesses:

NOTES:

  1. The GEOS-5 and MERRA data are kept at 72 vertical levels, and are only regridded to coarser horizontal resolution. However, GEOS-Chem has the capability to lump levels on the fly from 72 to 47 vertical levels. This is done for computational expediency.
  2. The new GEOS-5.7.2 data product was officially released in 2011. This data set has increased horizontal resolution (0.25° x 0.3125°), but the same # of vertical levels (72) as the older GEOS-5 and MERRA products.
  3. Please also see this document which details the evolution of the GEOS-5 system from GEOS-5.2.0/MERRA to GEOS-5.7.2 (aka "Fortuna").

References

  1. List of GEOS-5 met fields used by GEOS-Chem
  2. GEOS-5 issues encountered w/r/t GEOS-Chem
  3. Reprocessing of GEOS-5 met data for GEOS-Chem (completed Jul 2009)
  4. GEOS-5 products page at GMAO
  5. GEOS-5 File Specification Document (version 5.1.0)
  6. GEOS-5 File Specification Document (version 5.2.0)


--Bob Y. 16:33, 2 August 2011 (EDT)

GEOS-4

GEOS-4 was produced at higher vertical resolution but slightly coarser horizontal resolution than GEOS-3. There are approximately 20 years of GEOS-4 data available to be used with GEOS-Chem. GEOS-4 has been used extensively by the GEOS-Chem community in various applications.

Please see our GEOS-4 wiki page for more information.

Summary

Assimilation GCM used: NCAR fvCCM GCM
Native horizontal grid: 1° x 1.25°
Native vertical grid: 55 hybrid levels; model top at 0.01 hPa
Native file format: HDF4-EOS
Temporal coverage: 1985-2006; some 2007
We regridded to: 4° x 5° at 55 sigma layers
Strengths:
  • Long temporal horizon – 20 years of consistent met data
  • U and V winds are 6-hr averages, not instantaneous
  • Much better STE than any prior GEOS met fields
Weaknesses:
  • Convection variables totally different than GEOS–3
  • GMAO was unhappy w/ the convection results
  • Cloud OD’s are too low; J-values, chemistry are “too hot”

NOTES:

  1. The GEOS-4 data are kept at 55 vertical levels, and are only regridded to coarser horizontal resolution. However, GEOS-Chem has the capability to lump levels on the fly from 72 to 30 vertical levels. This is done for computational expediency.

References

  1. Documents which describe the validation of GEOS-4 met fields in GEOS-Chem
  2. GEOS-4 references
  3. List of GEOS-4 met fields
  4. Availability of GEOS-4 met fields

--Bob Y. 12:40, 29 July 2010 (EDT)

GEOS-3

Removal of support for GEOS-3

This update was tested in the 1-month benchmark simulation v9-01-03h and approved on 09 Mar 2012.

Bob Yantosca wrote:

As you may know, the GEOS-3 met (for data years 2000-2001) is now several versions behind the current GMAO operational product. If there is no longer a significant demand to keep GEOS-3 met, then I would propose removing the GEOS-3 specific source code (denoted by “#if defined( GEOS_3 )” statements). This will help to clean up the source code, which in turn will facilitate the work that Mike Long and I are doing on the Grid-Independent GEOS-Chem project.

Support for GEOS-3 meteorology will be removed in GEOS-Chem v9-01-03.

--Melissa Payer 12:18, 2 March 2012 (EST)

Summary

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

NOTES:

  1. The GEOS-3 data are kept at 48 vertical levels, and are only regridded to coarser horizontal resolution. However, GEOS-Chem has the capability to lump levels on the fly from 48 to 30 vertical levels. This is done for computational expediency.

--Bob Y. 12:41, 29 July 2010 (EDT)

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)

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