For CIME cases, how do we add constant initial conditions?

This is less of an issue and more of a question. In the scream_input.yaml file we are able to specify a constant initial value for a field by adding it to the list of args under `initial_conditions`. We use that to initialize things like `qm`. There is already a list of these in the `namelist_defaults.xml` file in the repo, (see example below) but given the way these are designated in the namelist file it isn't clear how you can add a new one "on the fly". My suspicion is you can't.

```

/usr/gdata/climdat/ccsm3data/inputdata/atm/scream/init/screami_ne30np4L72_20220823.nc
/usr/gdata/climdat/ccsm3data/inputdata/atm/cam/topo/USGS-gtopo30_ne30np4pg2_x6t-SGH.c20210614.nc
SMS_Ld1_P216x1.ne30pg2_ne30pg2.F2010-SCREAMv1.quartz_intel.test_u_v_U_V.scream
0.0
0.0
0.0
...
```