(Notes by Philip Cameron-Smith (Unlicensed) based on information from Mark Taylor and Kate Evans (Unlicensed), 2014-10-31)
The SE dycore runs on cubed-sphere grids (eg, NE30, NE120). The most accurate output is obviously on those native grids. However, plotting and analysis programs often only work with rectangular lat-lon output. And ACME-CAM may not put all of the necessary information into the output files necessary for general plotting and analysis tools.
ACME is currently working on an interim solution that involves a regridding tool that regrids the ACME-CAM output files before reading them into UVCDAT: /wiki/spaces/WORKFLOW/pages/3245930
Another alternative is to tell ACME-CAM to regrid the output onto a rectangular lat-lon grid before writing it out to the output file. This uses bilinear interpolation, which isn't ideal for every purpose, but is a testgood enough for many purposes.
This is setup in the user_nl_cam namelist, using the following namelist variables:
interpolate_analysis = .true.,.true.,.true.,.true.,.true.,.true.
interp_gridtype = 1 ! equal angle lat/lon grid, with point at pole (FV scalar grid)
interp_nlat=256
interp_nlon=512
This example will cause CAM to output onto a .5 deg grid.
The options for the output grid type are:
interp_gridtype = 1 equally spaced, including poles (FV scalars output grid)
interp_gridtype = 2 Gauss grid (CAM Eulerian)
interp_gridtype = 3 equally spaced, no poles (FV staggered velocity)
The interpolate_analysis options are for the different history tapes.
In the code there appears to also be an option for the type of regridding:
interp_type = 1 ! 0 = native high order, 1 = bilinear (default)
is included in Notes on tuning 1 degree ACME v0 model