GEOS-Chem restart files

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This page contains information about files produced by GEOS-Chem simulations, including diagnostic data and restart files used for initial conditions.


GEOS-Chem restart files contain the initial conditions for a GEOS-Chem simulation. There are two restart files for GEOS-Chem:

File(s) Format Description Notes
GEOSChem.Restart.YYYYMMDD_hhmmz.nc4 netCDF The GEOS-Chem restart file. Contains species concentrations that are read in at simulation startup.

GEOS-Chem writes a restart file at the end of each simulation. This allows a long simulation to be split into several individal run stages..

For example, the restart file that was created at 00:00 UTC on August 1, 2016 is named: GEOSChem.Restart.20160801_0000z.nc4. The z indicates "Zulu" or "Z" time, which is another name for UTC.

For more information, please see our GEOS-Chem restart files wiki page. netCDF The HEMCO restart file. The HEMCO emissions component will save out certain quantities (mostly pertaining to soil NOx and biogenic emissions) in order to facilitate long GEOS-Chem simulations with several run stages.

When you run a GEOS-Chem simulation, it will write new GEOS-Chem restart files at the intervals you specify in HISTORY.rc. New HEMCO restart files are written with frequency configured in HEMCO_Config.rc if HEMCO is used in your simulation.

GEOS-Chem run directories are configured to use initial GEOS-Chem restart files in netCDF format. These files are available for download at:

CAVEAT: The initial restart files do not reflect the actual atmospheric state and should only be used to "spin up" the model. In other words, they should be used as initial values in an initialization simulation to generate more accurate initial conditions for your production runs.

Doing a one year spin up is usually sufficient; however, we recommend ten years for ozone, carbon dioxide, and methane simulations, and four years for radon-lead-beryllium simulations. If you are in doubt about how long your spin up should be for your simulation, we recommend contacting the GEOS-Chem Working Group that specializes in your area of research.

You may spin up the model starting at any year for which there is met data, but you should always start your simulations at the month and day corresponding to the restart file to more accurately capture seasonal variation. If you want to start your production run at a specific date, we recommend doing a spin up for the appropriate number of years plus the number of days needed to reach your ultimate start date. For example, if you want to do a production simulation starting on 12/1/13, you could spin up the model for one year using the initial GEOS-FP restart file dated 7/1/13 and then use the new restart file to spin up the model for five additional months, from 7/1/13 to 12/1/13.

To determine the date of a netCDF restart file, you may use ncdump For example:

ncdump -v time -t

The -t option will return the time value in human-readable date-time strings rather than numerical values in unit such as "hours since 1985-1-1 00:00:0.0." The date of a binary punch restart file can be determined by opening the file in GAMAP.

Using a HEMCO restart file for your initial spin up run is optional. The HEMCO restart file contains fields for initializing variables required for Soil NOx emissions, MEGAN biogenic emissions, and the UCX chemistry mechanism. The HEMCO restart file that comes with a run directory may only be used for the date and time indicated in the filename. HEMCO will automatically recognize when a restart file is not available for the date and time required, and in that case HEMCO will use default values to initialize those fields. You can also force HEMCO to use the default initialization values by setting "HEMCO_RESTART" to false in HEMCO_Config.rc. For more information, see the HEMCO User's Guide.

--Melissa Sulprizio (talk) 12:25, 16 July 2019 (UTC)

Restart files in GEOS-Chem 12

These updates were included in GEOS-Chem 12.1.0, which was released on 26 Nov 2018.

In GEOS-Chem 12.1.0, several restart file updates were introduced. These include:

Restart collection in HISTORY.rc

GEOS-Chem restart files are now saved out via the History component. A new Restart collection has been defined in HISTORY.rc and fields saved out to the restart file can be modified in that file.

New restart file names

Because we are now using the History component to archive restart files in GEOS-Chem 12.1.0 and later versions, GEOS-Chem restart file names now use this nomenclature: GEOSChem.Restart.YYYYMMDD_hhmmz.nc4.

For example, the restart file that was created at 00:00 UTC on August 1, 2016 is named: GEOSChem.Restart.20160801_0000z.nc4. The z indicates "Zulu" or "Z" time, which is another name for UTC.

New variable names

Prior to GEOS-Chem 12.1.0, species names in restart files began with the SPC_ prefix:

 SPC_NO           # Initial concentration of NO
 SPC_O3           # Initial concentration of O3
 SPC_CO           # Initial concentration of CO
 SPC_CH4          # Initial concentration of CH4

In GEOS-Chem 12.1.0 and later versions, the species names now begin with the prefix SpeciesRst_ prefix:

 SpeciesRst_NO    # Initial concentration of NO
 SpeciesRst_O3    # Initial concentration of O3
 SpeciesRst_CO    # Initial concentration of CO
 SpeciesRst_CH4   # Initial concentration of CH4

--Bob Yantosca (talk) 15:16, 30 November 2018 (UTC)

New fields added to the GEOS-Chem restart file

Several new fields have been added to the GEOS-Chem output restart file in an attempt to remove differences between single and multi-segmented GEOS-Chem simulations.

Item Description
1 Module-level variables H2O2s and SO2s from wetscav_mod.F have been added to State_Chm (as State_Chm%H2O2AfterChem, StateChm%SO2AfterChem). These fields will be output to the GEOS-Chem restart file and then initialized to the values saved in the restart file at the start of the next simulation. Prior to this update, both H2O2s and SO2s were initialized to the H2O2 and SO2 tracer concentrations at the start of every simulation. This change will impact multi-segmented runs only.
2 Module-level variables DRY_TOTN and WET_TOTN from get_ndep_mod.F have been added to State_Chm (as State_Chm%DryDepNitrogen, StateChm%WetDepNitrogen). These fields will be output to the GEOS-Chem restart file and then initialized to the values saved in the restart file at the start of the next simulation. Prior to this update, both variables were initialized to zero at the start of every simulation. Storing them in the restart file may improve accuracy of soil NOx emissions over multi-segmented runs. This change will impact multi-segmented runs only.
3 Move State_PSC from the HEMCO restart file to the GEOS-Chem restart file.
4 Save out instantaneous met fields TMPU1, SPHU1, PS1DRY, PS1WET, DELPDRY to the GEOS-Chem restart file. These will be used to initialize the met fields at the start of the timestep, otherwise they will be set to the values of those fields at the end of the timestep.

While this update was added to GEOS-Chem Classic in 12.1.0, it will be added to GCHP in 12.2.0.

Read restart file via HEMCO

GEOS-Chem restart files are now read in via HEMCO. The entries listed below have been added to HEMCO_Config.rc (and may vary slightly for different simulation types). These fields are obtained from HEMCO and copied to the appropriate State_Chm and State_Met fields in the new routine Get_GC_Restart (found in GeosCore/hcoi_gc_main_mod.F90).

  # --- GEOS-Chem restart file ---
  # PSC state only needed for UCX
  * SPC_           ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 SpeciesRst_?ALL?    $YYYY/$MM/$DD/$HH CS xyz 1 * - 1 1
  * TMPU1          ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Met_TMPU1           $YYYY/$MM/$DD/$HH E  xyz 1 * - 1 1
  * SPHU1          ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Met_SPHU1           $YYYY/$MM/$DD/$HH E  xyz 1 * - 1 1
  * PS1DRY         ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Met_PS1DRY          $YYYY/$MM/$DD/$HH E  xy  1 * - 1 1
  * PS1WET         ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Met_PS1WET          $YYYY/$MM/$DD/$HH E  xy  1 * - 1 1
  * DELPDRY        ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Met_DELPDRY         $YYYY/$MM/$DD/$HH E  xyz 1 * - 1 1
  * KPP_HVALUE     ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Chem_KPPHvalue      $YYYY/$MM/$DD/$HH E  xyz 1 * - 1 1
  * WETDEP_N       ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Chem_WetDepNitrogen $YYYY/$MM/$DD/$HH E  xy  1 * - 1 1
  * DRYDEP_N       ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Chem_DryDepNitrogen $YYYY/$MM/$DD/$HH E  xy  1 * - 1 1
  * SO2_AFTERCHEM  ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Chem_SO2AfterChem   $YYYY/$MM/$DD/$HH E  xyz 1 * - 1 1
  * H2O2_AFTERCHEM ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Chem_H2O2AfterChem  $YYYY/$MM/$DD/$HH E  xyz 1 * - 1 1
  * STATE_PSC      ./GEOSChem.Restart.$YYYY$MM$DD_$HH$MNz.nc4 Chem_StatePSC       $YYYY/$MM/$DD/$HH E  xyz count       * - 1 1

The CS cycle flag was added as an option to HEMCO in GEOS-Chem 12.1.0 to tell HEMCO to skip fields that aren't found in the provided file. This is useful when certain species aren't found in the restart file and, in that case, GEOS-Chem will initialize that species to the background concentrations specified in the species database.

--Melissa Sulprizio (talk) 16:30, 7 November 2018 (UTC)

Viewing and manipulating restart files

For information on viewing and manipulating GEOS-Chem restart files in netCDF format, please see the following sections of our Working with netCDF data files wiki page:

  1. Resources for viewing and manipulating netCDF files
  2. Regridding netCDF files
  3. Adding a new species to a restart file
  4. Cropping restart files to a subset of the globe
  5. Chunking and deflating restart files

--Bob Yantosca (talk) 15:19, 30 November 2018 (UTC)

Previous issues that are now resolved

GAMAP can now read GEOS-Chem restart files in netCDF format

This update was included in GEOS-Chem v11-01 public release

Starting in GEOS-Chem v11-01, all restart files are now saved in COARDS-compliant netCDF format. We have had to make some minor modifications to both GEOS-Chem and GAMAP in order to allow GAMAP to read these files. The table below gives a summary of these modifications.

GEOS-Chem or GAMAP? File Modification
GEOS-Chem GeosCore/gamap_mod.F In routine INIT_TRACERINFO, we now write metadata for all species (advected or not) to the tracerinfo.dat file under the ND45 tracer concentration diagnostic section. Because the netCDF restart file contains concentrations for both advected and non-advected species, we need to make sure that the tracerinfo.dat file created by GEOS-Chem contains metadata for all species.
GAMAP internals/ The prior algorithm always assumed that a netCDF file would end in either .nc or .nc4. We now have removed this restriction. We now split the filename string on . and then examine the substrings for nc or nc4 (case-insensitive).
GAMAP internals/ Added some minor modifications to read netCDF restart files:
  1. Determine vertical grid from the number of layers (if the Model global attribute is not specified).
  2. Assign category DXYP to variable AREA, which is included in the netCDF restart file.
  3. Assign category IJ-AVG-$ to variables beginning with either SPC_ or TRC_. Also remove the SPC_ and TRC_ from the variable name internally so that the variable name will match the metadata in tracerinfo.dat.

--Bob Yantosca (talk) 19:29, 23 January 2017 (UTC)