Generating Restart Data

Restart data is generated automatically as the simulation progresses, at an interval determined by the setting of namelist variables.

• NHTFRQ --- This specifies the number of simulation hours (or time steps) between each history write.
• MFILT --- This specifies the number of history writes that make up a history volume.
• NREFRQ --- This specifies the number of completed history volumes between each restart write.
• NINAVG --- This allows the user to specify monthly averaging of history output, which also changes restart behavior. Restarts with monthly averaging are described separately in Section 5.3.3.

The number of restarts generated for a given length of simulation is determined by the number of complete history volumes written, which is in turn determined by the number of history writes per history volume, which is in turn determined by the number of history writes per hour of simulation. The default settings for these variables are as follows.

    NHTFRQ = -24,
    MFILT = 5,
    NREFRQ = 1,
    NINAVG = 'A',

These default settings result in the output of restart data every five model days. History is output every 24 model hours (NHTFRQ = -24), a history ``volume'' is finished every 5 outputs (MFILT = 5), and restart data is generated after every 1 completed volume (NREFRQ = 1). If, instead, one wishes to keep the same restart generation frequency but have only one history write per volume, the settings are as follows.

    NHTFRQ = -24,
    MFILT = 1,
    NREFRQ = 5,
    NINAVG = 'A',

Restart files.

%cat r0001.A.* > r0001.A

It is necessary to combine the files into a single Primary Restart Data file only if the model is to be restarted on a different number of processors.

Alternating restart files.

By default, PCCM2 generates restart data sets in sequence: r0001, r0002, r0003, and so forth as the model runs. However, if only the most recent restarts are needed, PCCM2 can generate them in alternating mode to save space. Setting the namelist variable ACCRST to .FALSE. causes the model to write and overwrite only two restart data sets, switching back and forth between them.

History regeneration data sets.

Unlike CCM2, PCCM2 acquires all information for the restarted run from the namelist and from the restart data sets; it does not read previously generated history files, nor does it write or read history regeneration restart files. History regeneration runs and restarts within averaged periods are not supported.