Ability to output initial condition file

[whannah1]

EAM has the ability to create an initial condition file at specfied frequency via the inithist namelist variable. It would be useful to implement similar functionality in SCREAM in order to perform staged adjustment of new initial conditions.

[PeterCaldwell]

It seems like it would be trivial to convert a restart file into an IC file or to modify initialization routines to allow this?

[bartgol]

So, there are three options, I think:

1. Add capability to create an output stream with IC data. This is not the same as a restart file, b/c IC files are on physics GLL grid, while restart files have some PG2 and some dyn grid data.
2. Add capability to read restart file as an IC file. This is non-trivial, since we need to use some FvGll remap stuff, but it currently hard codes only the 2 scenarios we have: IC on GLL or Restart on PG2/Dyn.
3. Create a post processing script that converts a restart file to an IC file. This is also non-trivial, since PG2->GLL requires some projection matrices, so it's not just a matter of "stripping some fields".

All in all, I think option 1 is the easiest to implement, but it comes at a cost of increased runtime and increased output footprint. Maybe, we could go with option 4:

4. Create a standalone executable, that loads a restart file and spits out an IC file, calling the proper FvGll remap routines to convert PG2->DYN->GLL.

[PeterCaldwell]

@bartgol - I think the current plan is option 5 - see if it is easy to just restart EAMxx with a new case name and new YAML settings. Noel is testing that now. If option 5 doesn't work, then we'll loop back to your options 1-4. If we do that, my money is on option 4.