The model cycles thru netCDF data files containing all the data the coupler expects from a land model. Each file contains one year's worth of data consisting of 12 sets of mean monthly fields. This input data must have the same domain (resolution and coordinate arrays) as the latm model. The model can cycle thru a multi-year sequence of data. Generally the input data files are created from history files that are output from the CCSM's active land component model (CLM or LSM). These files could, hypothetically, be replaced by other data files that are in the same format. Because netCDF files are self describing, one can query the file itself for specifics about the file format.
On startup, the model reads in domain data from a netCDF file. Data exchanged with the coupler will be on the model domain. This file contains x & y coordinate arrays. The model uses a rectilinear grid with 2d coordinate arrays x(i,j) & y(i,j). Because the input land data (above) is on the same domain as the datm model, and because the input land data contains domain information, any input land data file can also serve as a domain data file. Normally the first file in the input data file sequence is used as 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 sequence of input land data files. See the section on input namelist variables for a complete list and description of namelist parameters.