Remapping restarts from one unstructured mesh to another

JanStreffing commented 2 years ago

It would be useful to have a tool or script to remap an existing FESOM2 restart from one unstructured mesh to another. Example applications that come to my mind:

Using running long and expensive spun up ocean states with new and improved meshes, e.g. https://github.com/FESOM/fesom2/issues/169#issuecomment-934503060.
Using a mid-resolution simulation to generate a spinup for high resolution run that can only be integrated for a few years due to cost.
Changing the ocean basin in between restarts due to evolving ice sheets.

I am under the impression that we currently have no such script or tool, is that correct? Is there a fundamental problem, e.g. with remapping the vector fields that's keeping us from attempting this, or is it a question of time and priority?

helgegoessling commented 2 years ago

Once "grid desciption files" for both meshes are available, it should in principle be easy to do that with CDO, e.g., with the operators remapycon and intlevel. However: (1) I'm not sure whether the meta data, dimension order, and so remain such that FESOM2 can still use the resulting remapped file directly for the restart. Otherwise a subsequent step might need to take care of "fixing" such things. (2) The remapped vector fields should be fine as long as the velocities are defined relative to a rotated pole (such that both poles are over land). Is that the case for FESOM2 restart files?

I'm not sure whether something like this is already in place outside CDO, e.g., using pyfesom or such...

koldunovn commented 2 years ago

Should be relatively easy to make with CDO or python interpolation. Not sure we even need interpolation of velocities. We just have to experiment a bit, and find time for this. It will be easier when implementation of functionality you describe in #189 is in place.

FESOM / fesom2

Remapping restarts from one unstructured mesh to another #197