The data ice model requires two input netCDF datasets: a domain dataset specifying the model grid domain and an SST dataset. The SST dataset contains 12 months of climatological SST data.
The ice model state variable ice fraction (equivalently, ice extent) is derived from input SST data. On startup, this model reads in SST data from a netCDF file. This file contains 12 months of SST data (presumably monthly mean fields) on a global 2x2 degree grid. An SST data file is provided with the distribution. This file contains Shea, Trenberth, & Reynolds (STR) SST climatology data. The file provided can be replaced by any other SST data file that is in the same format. Because netCDF files are self describing, one can query the file itself for specifics about the file format.
Note: if the CCSM configuration consists of a dummy ocean and a dummy ice model (e.g. coupled to active atmosphere and land models), normally one would coordinate the ice model's SST data with the ocean model's SST data so that the SST's and ice extent were consistent.
On startup, this model reads in domain data from a netCDF file. Data exchanged with the coupler will be on this model domain. This file, called data.domain.nc, contains x & y coordinate arrays as well as a domain mask. This model uses a latitude/longitude grid only, with 2d coordinate arrays x(i,j) & y(i,j), and a 2d domain mask mask(i,j). The domain must be a rectilinear grid, but needn't be a latitude/longitude grid. A mask value of 0 indicates land points (i.e. not in the model's domain). The ice data described above is interpolated onto the domain specified by the domain data file - all data exchanged with the coupler is on the domain specified by the domain data file.
On startup, the model reads an input namelist parameter file from stdin. The model has very few input namelist parameters. Typically the only input parameters that are required are those that specify how often the model will communicate with the coupler, and those that specify the input data files. Some can also alter the fluxes sent to the coupler. See the section on input namelist variables for a complete list and description of namelist parameters.