Topography in the dry dynamical core

Note, these instructions are only valid for the 2018 CESM2 release. If you wish to run the Held-Suarez configuration prior to the CESM2 release, please contact Isla Simpson (islas@ucar.edu)

In order to use topography with the dry dynamical core you must set the following in $CASEDIR/user_nl_cam

use_topo_file=.true.
bnd_topo="location_of_your_topo_file"

The topography file that you point to with bnd_topo must contain the variable PHIS (surface geopotential) in units of m2/s2 at the appropriate horizontal resolution. If you wish to use real world topography, you can simply point to the relevant topography file in your CESM input directory

$INPUTDIR/atm/cam2/topo/
where $INPUTDIR refers to the location of CESM input files on your machine. For users running on cheyenne, this is located at
/glade/p/cesmdata/cseg/inputdata/atm/cam/topo
On other machines, you can find out the location of $INPUTDIR by executing the following command from your case directory
./xmlquery DIN_LOC_ROOT
If you do not already have the topography input downloaded for your desired resolution, you can find information on obtaining input data here and here. If you wish to use idealized topography, the real world topography inputs to CAM can be a guide as to the format of the topography input and the resolution needed.

Note: an issue was introduced in the CESM2.1 series were reading in custom tropography no longer works out of the box. This issue has been fixed in the CESM2.2 release