The thermodynamic calculations involve one grid point at a time (see module
) so that a purely thermodynamic model integration is bit-for-bit
independent of the domain decompostion (i.e. the exact values of
), while the
dynamic calculation depends bit-for-bit upon domain boundary conditions, and therefore
on the exact values of
and
. The sea ice model climate is not sensitive to
the precise domain decomposition.
The actual source code uses and
for
and
respectively,
referring to the number of processors in the x direction and in the y direction
(these parameters are set by a pre-compiler; see the CSIM User's Guide Version 4).
The module
defines the local subdomain dimensions and their
beginning/ending indices. Module
computes and assigns the subdomain
processor numbers. The module
assigns the global domain values.
The module handles the 'unpacking' and 'packing' of the data
horizontally after and before exchange with the coupler. This involves excluding
latitude bands around the equator that have no sea ice present. Information on the
number of latitude bands of data for each hemisphere (i.e. the number of latitude
bands of actual hemispheric sea ice but with sufficient equatorwards bands to allow
for ice formation along ice edge as well) is included in the data exchange header.
As the areas where new ice formation will occur are known to the coupler (based
on the freeze/melt potential received from the ocean model), the coupler is able
to determine the precise latitude limits. Regions with no ice in the unpacked
fields are simply filled with zeros after being received from the coupler.