6.18.2 Invoking exch2

To use exch2 with the cubed sphere, the following conditions must be met:

The exch2 package is included when genmake2 is run. The easiest way to do this is to add the line exch2 to the profile.conf file - see Section 3.5 Building the code for general details.

An example of W2_EXCH2_TOPOLOGY.h and w2_e2setup.F must reside in a directory containing files symbolically linked by the genmake2 script. The safest place to put these is the directory indicated in the -mods=DIR command line modifier (typically ../code), or the build directory. The default versions of these files reside in pkg/exch2 and are linked automatically if no other versions exist elsewhere in the build path, but they should be left untouched to avoid breaking configurations other than the one you intend to modify.

Files containing grid parameters, named tile00.mitgrid where =(1:6) (one per subdomain), must be in the working directory when the MITgcm executable is run. These files are provided in the example experiments for cubed sphere configurations with 3232 cube sides - please contact MITgcm support if you want to generate files for other configurations.

As always when compiling MITgcm, the file SIZE.h must be placed where genmake2 will find it. In particular for exch2, the domain decomposition specified in SIZE.h must correspond with the particular configuration's topology specified in W2_EXCH2_TOPOLOGY.h and w2_e2setup.F. Domain decomposition issues particular to exch2 are addressed in Section 6.18.3 Generating Topology Files for exch2 and 6.18.4 exch2, SIZE.h, and Multiprocessing; a more general background on the subject relevant to MITgcm is presented in Section 4.3.1 Specifying a decomposition.

At the time of this writing the following examples use exch2 and may be used for guidance:

verification/adjust_nlfs.cs-32x32x1
verification/adjustment.cs-32x32x1 
verification/aim.5l_cs
verification/global_ocean.cs32x15
verification/hs94.cs-32x32x5

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