Are 3 grid configurations possible

[hines_91@osu_edu]

That is, having the atmosphere, land and ocean grids all different. I've been trying this (first with 4x5_T42_gx3v7) - editing the various templates and xml's. It's tough figuring out which domain.ocn and domain.lnd files to put in which place. Ultimately, I got past the compile and set-up issues, but it fails in the runtime stage - one way it complained that NX and NY in a domain file didn't match the expected total array size. Rearranging the domain files - perhaps I got past that, but then it complained ice grid mask didn't match the land grid mask. I couldn't track the error any farther since there was no tracer to the domain.ocn and domain.lnd files involved, nor was there a tracer to the horizontal spot were the error occurred.

Is it even possible to run with 3 grids? There are listings in the grid compsets that suggest this, but it requires many file edits to even attempt this. Perhaps it cannot be done?

Edit: I see now there is something in the documentation about "Trigrid Configurations." However, getting the correct domain.lnd and domain.ocn files appears to be a problem.

 

[zarzycki@umich_edu]

Yes, trigrid coupling is possible.

If you are creating a new trigrid setup, you need to modify two files.

1.) horiz_grid.xml file in $CCSMROOT/scripts/ccsm_utils/Case.template/. You will need to specify the domain files here. There are plenty of examples (in that file) as to how this should be handled.

2.) The coupler maps. In the current beta version of CESM they are in models/drv/bld/namelist_files/namelist_defaults_drv.xml (in 1.0.4 they may be somewhere else -- you can do a grep of the below template to find out where).

cpl/gridmaps/ne240np4/map_ne240np4_to_tx0.1v2_aave_110419.nc
cpl/gridmaps/ne240np4/map_ne240np4_to_tx0.1v2_aave_110419.nc
cpl/gridmaps/ne240np4/map_ne240np4_to_tx0.1v2_aave_110419.nc
cpl/gridmaps/tx0.1v2/map_tx0.1v2_to_ne240np4_aave_110419.nc
cpl/gridmaps/tx0.1v2/map_tx0.1v2_to_ne240np4_aave_110419.nc
cpl/gridmaps/ne240np4/map_ne240np4_to_fv0.23x0.31_aave_110419.nc
cpl/gridmaps/ne240np4/map_ne240np4_to_fv0.23x0.31_aave_110419.nc
cpl/gridmaps/fv0.23x0.31/map_fv0.23x0.31_to_ne240np4_aave_110419.nc
cpl/gridmaps/fv0.23x0.31/map_fv0.23x0.31_to_ne240np4_aave_110419.nc

Here you will need to replace your atm2ocn or lnd2atm with the appropriate map files. If they already exist in the CESM repository, then you just need to shuffle around the paths to match up with what you want -- otherwise you have to generate your own mapping files.

(NOTE: There is possibly a more "official" way of doing this -- I can just vouch that this works for me on NCAR's computers)