Namelist Variables

CICE uses the same namelists for both the coupled and uncoupled models. This section describes the namelist variables in the namelist ice_nml, which determine time management, output frequency, model physics, and filenames The ice namelists for the coupled model are now located in $CASE/Buildconf.

A script reads the input namelist at runtime, and writes the namelist information to the file ice_in in the directory where the model executable is located. Therefore, the namelist will be updated even if the ice model is not recompiled. The default values of the ice setup, grid, tracer, and physics namelists are set in ice_init.F90. The prescribed ice and aerosol options along with the history namelist variables are set in ice_prescribed.F90, ice_prescaero.F90, and ice_history.F90 respectively. If they are not set in the namelist in the script, they will assume the default values listed in Tables 1-9, which list all available namelist parameters. The default values shown here are for the coupled model, which is set up for a production run. Only a few of these variables are required to be set in the namelist; these values are noted in the paragraphs below. An example of the default namelist is shown in Section 3.10.1.

**Table 1:** Namelist Variables for Run Management
Varible	Type	Default Value	Description
`ice_ic`	character	default	Filename for initial and branch runs
			'default' uses default initialization
			'none' initializes with no ice
`xndt_dyn`	Integer	1	Times to loop through (sub-cycle) ice dynamics
`diagfreq`	Integer	24	Frequency of diagnostics written (min, max, hemispheric sums) to standard output
			24 => writes once every 24 timesteps
			1 => diagnostics written each timestep
			0 => no diagnostics written
`histfreq`	Character Array	'm','x','x','x','x'	Frequency of output written to history streams
			'D' or 'd' writes daily data
			'W' or 'w' writes weekly data
			'M' or 'm' writes monthly data
			'Y' or 'y' writes yearly data
			'1' writes every timestep
			'x' no history data is written
`histfreq_n`	Integer	1,1,1,1,1	Frequency history data is written to each stream
`hist_avg`	Logical	.true.	If true, averaged history information is written out at a frequency determined by histfreq. If false, instantaneous values rather than time-averages are written.
`pointer_file`	Character	'rpointer.ice'	Pointer file that contains the name of the restart file.
`lcdf64`	Logical	.false.	Use 64-bit offset in netcdf files

The main run management namelist options are shown in Table 1. While additional namelist variables are available in the uncoupled version, they are set by the driver in CCSM. Variables set by the driver include: dt, runid, runtype, istep0, days_per_year, restart and dumpfreq. These should be changed in the CCSM configuration files: