Restart options

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Restart and Save files

The two main types of restart files are "restart" and "save" files. They differ in accuracy and flexibility of use.

Accuracy: The restart files store data in double precision (same precision as the tracers in the run itself), while save files store them in single precision. They also store the air mass and the pressure fields. Then, when cutting a run into two or more chunks, using restart file gives the same results as the run done in one go. This is not the case with save files.

Flexibility: The restart files are tied to a date and a resolution, and consequently their file name follow the TM5_restart_YYYYMMDD_HHMM_<region-name>.nc format. You cannot use them for a different region/resolution. On the opposite, save files can be use to start a run with a different grid resolution and for any date. Their name can be anything. Finally, missing tracers are not handled when reading a restart, but will be filled with a tiny number when not present in a save file.

UPDATE, TM5-MP only: restart files can be used for a different start date and/or resolution and/or met fields driver (ei, od, ec-earth). You just need to rename the restart file with the correct date and resolution, and set istart=32. Update 2018-02-20: TM5-MP users do not need to use save files (istart=31) anymore. The two cases when it was still useful:

can now use restart files, the latter with istart=32.

Currently, TM writes either a restart or a save file, but not both, at the end of run. See Spinup and zoom regions for solving potential issues.

Rc file settings

Settings for the initial state of the atmospheric tracers are found in the "Restart files" section of the main rc file. The section also deals with the restart files being written by the run.

  1  !=====================================================================!
  2  ! Restart files
  3  !=====================================================================!
  4  ! initial fields
  5  istart              : 33
  6  ! Directory (case of istart=33 or 32)
  7    : /path/to/TM56_input/testdata_restart/
  8  ! File (case of istart=4, 30, 31, 5)
  9  start.31.glb300x200 : /path/to/TM56_input/testdata_restart/m7_save_2007010100_glb300x200.hdf
 11  restart.write                 :  T
 12  ! extra restart files
 13  restart.write.extra           :  F
 14  restart.write.extra.hour      :  00
 15  restart.write.extra.dhour     :  24
 16  ! where to write restart files:
 17  restart.write.dir             :  ${}/restart
 18  ! ensure creation of directory;
 19  restart.install.dir           :  ${restart.write.dir}

line 5: the istart key defines how the tracers are set at the beginning of a run. Possible values are:

|  1 | initial fields set to 0.                                                                                                                      |
|  2 | initial fields computed in sources_sinks/trace1 (TM5: peudo-random values based on processor rank, TM5-MP: very tiny non-zero value)                            |
| 30 | read from save file specified in rc file with start.30.<region-name> : read vmr/slopes/secondmom only for transported tracers. No regridding available  |
| 31 | initial mass of transpoted AND short lived species read from save file, no slopes, but regridding available, since grid information is also read   |
| 32 | read from restart file (only tracers mass). Allows remapping and different start date.                                                        |
| 33 | read from restart file                                                                                                                        |
|  4 | with initial fields read from model output stored in mixing ratio (no slopes), in a so-called "saveoldfile".                                  |
|  5 | with initial fields (transported only) read from an mmix output file in mixing ratio (no slopes, missing field set to zero)                   |
|  9 | user defined in module 'user_input'                                                                                                           |

Most important and used values are 31, 33 and 5.

line 7: only used if istart=33. Indicates the directory where to find the restart file to read for the first chunk of your run. Other restart files written at the end of a run can be somewhere else, see line 17.

line 9: only used if istart=4, 30, 31, or 5. In which case the key provides the fully qualified name of the file to read. Note that:

line 11: if set to T (true), then restart files are written at the end of each chunks. If false, then save files are written instead.

line 13-15: you can have restart file written at time step(s) other than the end of the run. Set restart.write.extra to T to have additional restart files every restart.write.extra.dhour, and at the restart.write.extra.hour hour. The later, if set to 00, is useful to create a restart file from a save file or another restart file tied to a different date.

line 17: specifies the directory where restart or save files are written.

line 19: leave this key as is. It is used to create the restart directory if missing.

Spinup, resolution and zoom regions

If you spin up your model at coarser resolution, or if you spin up your model without zoom regions, but plan to have zoom regions in your production run, you should not write restart file:

restart.write : F

Then you have a save file at the end that can be used for all regions.

Note that you can still start the spin-up from a restart (istart=33), since the keys are independent.

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