GEOS-Chem Online User's Guide

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GEOS-Chem v11-02-final will also carry the designation GEOS-Chem 12.0.0. We are migrating to a purely numeric versioning system in order to adhere more closely to software development best practices. For a complete description of the new versioning system, please see our GEOS-Chem version numbering system wiki page.

11. Meteorological Fields

You can use several different assimilated meteorological data products to drive GEOS-Chem simulations. For more information, please consult the following GEOS-Chem wiki resources:

Met data product Wiki Documentation
(aka GEOS-5 "forward processing")

These have been de-supported in GEOS-Chem 12.0.0 (aka v11-02-final), per request of NASA/GMAO.

Dear GEOS-Chem user:

I write address some confusion about the different GEOS meteorological datasets produced by NASA GMAO and used by GEOS-Chem.

The two main data archives that you should use for your GEOS-Chem simulations are:

  1. The operational data stream from the GEOS Forward Processing (0.25° x 0.3125°, 72 levels) starting in 2012, which should be called GEOS-FP;
  2. The consistent MERRA-2 reanalysis for 1979-present (0.5° x 0.625°, 72 levels).

GEOS-Chem also supports older GEOS data sets including GEOS-4, GEOS-5, and MERRA. These are of inferior quality and GMAO does not want us to use them. They can still be useful to characterize model transport errors or the effects of different met fields for the same year, but should not be used for any other applications.

For more information see the GEOS-Chem narrative description at

Daniel Jacob
02 Jun 2017

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