restart-files-what.rst

What is a restart file?

Restart files contain the initial conditions (cf. :ref:`init-cond`) for a GEOS-Chem simulation. GEOS-Chem simulations need two restart files.

.. option:: GEOSChem.Restart.YYYYMMDD_hhmmz.nc4

   **Format:** netCDF

   **Description:**  The :ref:`GEOS-Chem Classic restart file
   <restart-files-gc>`. Contains species concentrations that are read
   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, 2019 is named:
   :file:`GEOSChem.Restart.20190801_0000z.nc4`.  The :file:`z`
   character  indicates "Zulu" time (aka UTC).

   GEOS-Chem restart files are created in the :option:`Restarts/`
   folder of your :ref:`GEOS-Chem run directory <rundir>` directory.

.. option:: HEMCO_restart.YYYYMMDDhhmm.nc

   **Format:** netCDF

   **Description:** The :ref:`HEMCO restart file <restart-files-hco>`.
   HEMCO archives certain quantities  (mostly pertaining to soil NOx
   and biogenic emissions) in order to facilitate long  GEOS-Chem
   simulations with several run stages.

   HEMCO restart files are created in the :option:`Restarts/`
   folder of your :ref:`GEOS-Chem run directory <rundir>` directory.

When you run a GEOS-Chem simulation, it will write new GEOS-Chem restart files at the intervals you specify in :ref:`HISTORY.rc <cfg-hist>`. New HEMCO restart files are written with frequency configured in :ref:`HEMCO_Config.rc <cfg-hco-cfg>`.

Viewing and manipulating restart files

Please see the following sections of our Supplemental Guide: :ref:`ncguide` for more information on how you can view and manipulate data in restart files:

1. :ref:`ncguide-useful-tools`
2. :ref:`ncguide-regridding`
3. :ref:`ncguide-adding-new-var`
4. :ref:`ncguide-cropping`
5. :ref:`ncguide-chunk-deflate`