8. Data Ice (DICE)¶

DICE is a combination of a data model and a prognostic model. The data functionality reads in ice coverage. The prognostic functionality calculates the ice/atmosphere and ice/ocean fluxes. DICE receives the same atmospheric input from the coupler as the active CICE model (i.e., atmospheric states, shortwave fluxes, and ocean ice melt flux) and acts very similarly to CICE running in prescribed mode. Currently, this component is only used to drive POP in “C” compsets.

8.1. xml variables¶

The following are xml variables that CIME supports for DICE. These variables are defined in $CIMEROOT/src/components/data_comps/dice/cime_config/config_component.xml. These variables will appear in env_run.xml and are used by the DICE cime_config/buildnml script to generate the DICE namelist file dice_in and the required associated stream files for the case.

Note

These xml variables are used by the the dice’s cime_config/buildnml script in conjunction with dice’s cime_config/namelist_definition_dice.xml file to generate the namelist file dice_in.

“DICE xml variables”¶
xml variable	description
DICE_MODE	Mode for sea-ice component
	Valid values are: null, prescribed, ssmi, ssmi_iaf, ww3

8.2. datamode values¶

The xml variable DICE_MODE (described in DICE_MODE, datamode and streams) sets the streams that are associated with DICE and also sets the namelist variable datamode. datamode (which appears in shr_strdata_nml) specifies what additional operations need to be done by DICE on the streams before returning to the driver.

Each data model has its own set of supported datamode values. The following are the supported DICE datamode values, as defined in the file namelist_definition_dice.xml.

“Valid values for datamode namelist variable”¶
datamode variable	description
NULL	Turns off the data model as a provider of data to the coupler. The ice_present flag will be set to false and the coupler will assume no exchange of data to or from the data model.
COPYALL	The default science mode of the data model is the COPYALL mode. This mode will examine the fields found in all input data streams; if any input field names match the field names used internally, they are copied into the export array and passed directly to the coupler without any special user code. Any required fields not found on an input stream will be set to zero.
SSTDATA	Is a prognostic mode. It requires data be sent to the ice model. Ice fraction (extent) data is read from an input stream, atmosphere state variables are received from the coupler, and then an atmosphere-ice surface flux is computed and sent to the coupler. It is called `SSTDATA` mode because normally the ice fraction data is found in the same data files that provide SST data to the data ocean model. They are normally found in the same file because the SST and ice fraction data are derived from the same observational data sets and are consistent with each other.

8.3. DICE_MODE, datamode and streams¶

The following table describes the valid values of DICE_MODE (defined in the config_component.xml file for DICE), and how they relate to the associated input streams and the datamode namelist variable. CIME will generate a value of DICE_MODE based on the compset.

“Relationship between DICE_MODE, datamode and streams”¶
DICE_MODE, description-streams-datamode”
null	null mode
	streams: none
	datamode: null
prescribed	prognostic mode - requires data to be sent to DICE
	streams: prescribed
	datamode: SSTDATA
ssmi	Special Sensor Microwave Imager climatological data
	streams: SSMI
	datamode: SSTDATA
ssmi	Special Sensor Microwave Imager inter-annual forcing data
	streams: SSMI_IAF
	datamode: SSTDATA
ww3	ww3 mode
	streams: ww3
	datamode: COPYALL

NIf DICE_MODE is set to ssmi, ssmi_iaf or prescribed, it is a prognostic mode and requires data be sent to the ice model. Ice fraction (extent) data is read from an input stream, atmosphere state variables are received from the coupler, and then an atmosphere-ice surface flux is computed and sent to the coupler. Normally the ice fraction data is found in the same data files that provide SST data to the data ocean model. They are normally found in the same file because the SST and ice fraction data are derived from the same observational data sets and are consistent with each other.

8.4. Namelists¶

The namelist file for DICE is dice_in (or dice_in_NNN for multiple instances).

As is the case for all data models, DICE namelists can be separated into two groups, stream-independent and stream-dependent.

The stream dependent group is shr_strdata_nml.

The stream-independent group is dice_nml and the DICE stream-independent namelist variables are:

decomp	decomposition strategy (1d, root) 1d => vector decomposition, root => run on master task
flux_qacc	activates water accumulation/melt wrt Q
flux_qacc0	initial water accumulation value
flux_qmin	bound on melt rate
flux_swpf	short-wave penetration factor
restfilm	master restart filename
restfils	stream restart filename
force_prognostic_true	TRUE => force prognostic behavior

To change the namelist settings in dice_in, edit the file user_nl_dice.

8.5. Streams independent of DICE_MODE value¶

There are no datamode independent streams for DICE.

8.6. Field names¶

DICE defines a set of pre-defined internal field names as well as mappings for how those field names map to the fields sent to the coupler.

Note

In general, the stream input file should translate the stream input variable names into the docn_fld names below for use within the data ocn model.

“DICE internal field names”¶
dice_fld (avifld)	driver_fld (avofld)
ifrac	Si_ifrac