NUOPC driver

We have adopted the NUOPC driver from CESM.

Component initialisation

Model component initialisation strategy is specified through a combination of flags set in the nuopc.runconfig configuration file and the input parameter files for each component.

The start_type parameter in the ALLCOMP_attributes section of nuopc.runconfig can be set to one of three values (note that the access-om3 Payu driver automatically sets this parameter depending on whether the run is an initial or restart run):

• "startup" specifying an initial run,
• "continue" specifying a run starting from restart files,
• "branch" specifying a run starting from restart files in which properties of the output history files may be changed - not used here.

These have the following effects on each ACCESS-OM3 component’s parameters settings:

MOM6

See MOM6 NUOPC cap for details.

start_type	Interaction with model parameters (from input.nml)
"startup"	Sets parameter restartfiles = "n".
"continue" / "branch"	Hardcoded to use restart file specified in a local file rpointer.ocn.

Note, users should let NUPOC set the restartfiles parameter. It should not be specified in input.nml.

CICE6

See CICE6 NUOPC cap for details.

start_type	Interaction with model parameters (from ice_in)
"startup"	Sets parameter runtype = "initial". The type of CICE startup can be further configured using the ice_ic parameter in ice_in - see here.
"continue" / "branch"	Sets parameters restart = .true. , runtype = "continue" and use_restart_time = .true. so uses restart specified in file specified in parameter pointer_file.

Note, users should let NUPOC set the restart, runtype and use_restart_time parameters. They should not be specified in ice_in.

CDEPS components (DATM, DROF)

See e.g. the atm NUOPC cap and here for details.

start_type	Interaction with model parameters (from d{model_name}_in)
"startup"	Does not attempt to read any restarts regardless of parameter values.
"continue" / "branch"	If parameter skip_restart_read = .false., then reads restart specified in file rpointer.{model_name} or reads restart specified in parameter restfilm if it isn't set to "null" - see here.

Note, restarts are used for the CDEPS components in ACCESS-OM3 only for performance reasons. They’re not needed to restart exactly, but they reduce startup cost associated with reading the input dataset time axis information - see here for more detail.