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What's a model restart?

Excerpt

A restart allows the model to continue a forecast with a succession of  individual runs, each one starting where the other one left off. e.g. running an extended forecast of 100 days with 5 separate runs of 20 days each.

A restart will always be exact, that is, the results of the restarted forecast should always match a single run of the model for the same total length (assuming all settings remain the same).

This page describes how to configure and use the model restart facility.n.b. the

Warning

The restarted run must always have the same parallel decomposition (TASKS x THREADS) otherwise the restart will fail.

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The value of NFRRES is normally set to 1 if using NRESTS. If NFRRES is set > 1 it is multiplied to the restart time. In the above example, if NFRRES was changed to 2, the model would still give 3 restart files but this time at 96hrs, 240hrs and 384hrs.

Files created

Restart files

The output files all begin with the name 'srf'. One file will be created per MPI task. The files are written as unformatted binary (not GRIB) in order to preserve precision.

The file name includes a date as : srfddddhhmm, where dddd is the day number of the run, hh is the hour and mm is the minutes. e.g. srf00000120.0002 would be for day 1 and 20mins into the run written from MPI task 2.

Deletion of old restart files

By default, old restart files are not deleted which might be a concern at high resolutions. One . This might cause problems with limited file quotas e.g. one restart file at T1279 is approx 500Mb when using 128 MPI tasks, giving a total restart file requirement of approx 64Gb per output instance. Changing

To change this behaviour is not possible via NAMRES. Instead, edit the namelist file ifs/setup/sures.F90 fort.4 and change the default value of LDELRES to TRUE. This will be changed for a future release of OpenIFS.. e.g.

&NAMRES
    LDELRES=.true.,
/

Restart namelist

A file, 'rcf' will be created by the model at each timestep when the restart files are written. This file contains the NAMELIST NAMRCF that informs the model what it needs to know to restart the model.

Info

If the file rcf is present in the same directory as the restart files (srf*), the model will always assume it is doing a restart.

Do not delete this file, otherwise the model will be unable to restart - regardless of whether the actual restart files (those beginning with srf) are present.

Conversely, if you don't want to run a restart but want to repeat the run, do delete rename the rcf file (e.g. rcf.old) or delete it (and the srf files). If you don't the model will attempt to continue the run according to the namelist in the rcf file as this takes precedence over the namelists read from fort.4.

Changing location or name of restart files

The restart file by default is written to the same directory as the model grib output files. The files all begin with the prefix 'srf'.

To change this prefix or the directory the files are written to, use the CIOSPRF character variable in the namelist NAMIOS:

Code Block
&NAMIOS
   CIOSPRF='./myrestarts/srf',
/

How to use a specific restart

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