2 Input Datasets

2.1 Atmospheric Data

The latm will cycle through a given set of state, precipitation, and radiation data sets. Each of these three data streams must have the same spatial resolution, e.g. T62, but the can differ in their temporal resolutions. For example, the state and precipitation data sets can be 6-hourly and monthly data, respectively. In its present configuration, the latm uses NCEP reanalysis data sets for all three forcing streams. The state variables consist of zonal and meridional 10m winds, surface 2m (extrapolated to 10m) air temperature, specific humidity, and density. The radiation data sets are long-wave down, short-wave down, and short-wave up.

All of the forcing information is set-up using four namelist variables per forcing type:

1. data_dir[1...3]: a directory path for the forcing data files. It must include the name of the data source in capital letters, e.g. "NCEP."
2. data_year0[1...3]: the 1st year in the data sequence, e.g. 1985.
3. data_oyear[1...3]: the simulation year matched to year0, e.g. 1.
4. data_nyear[1...3]: the number of years in the sequence, e.g. 2.

So, in the above example, the NCEP reanalysis fields for 1985 (corresponding to simulation year 1) and 1986 will be cycled through continuously. The array indices of the these namelist variables correspond to state, precipitation, and radiation data streams, respectively.

Note that this version of latm can only use NCEP data for all three data streams and the biases in these data produce solutions that are not of high scientific quality. The latm code is provided as an example of how one group of users altered the datm source code to cycle through different types of input data streams.

2.2 Domain Data

On startup, the model reads in domain data from the forcing data files. Data exchanged with the coupler will be on this 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).

2.3 Namelist

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 atmosphere data files. See the section on input namelist variables for a complete list and description of namelist parameters.