WRF save files for future ndown run

[janac4]

Hello everyone,

I'm familiar with WRF model and run daily a two domain model using one-way nesting. I wanted to know which files should I save from this first 2-domain run in case in a future I want to run a d03 domain with ndown (using wrfout files from d02).
If I don't know the final domain (I can't create met_em files right now), what should I save from WPS?
If I knew the domain, could I just save wrfinput and wrfbdy files from real.exe with all three domains? Would I need met_em files?
Also, I wanted to know which met_em files are mandatory when running a ndown simulation. I read somewhere that for d02 domain end_date could be set as start_date, so just one met_em.d02* would be generated. Is it true? However, if in the future I want to run a d03 domain, should I also execute all met_em files for d02?
Sorry about the chaotic questions, I'm looking for an optimal way to get my idea without having to run again the whole simulation.

Thanks a lot.

 

[kwerner]

Hi,
I'll attempt to answer your questions below:

If I don't know the final domain (I can't create met_em files right now), what should I save from WPS?

If you still need to go back and create a 3rd domain, then you will need to save the intermediate files created by ungrib, and you'll want to save all of your WPS output so that you can run through the real.exe process later. You will need to run geogrid.exe again, but you can use the namelist variable "active_grid = .false., .false., .true." in the &share namelist record to indicate that you only need new output for d03. You will NOT need to re-run ungrib.exe because it only processes data files, which are not domain-dependent. Then when you run metgrid.exe, you can keep the same "active_grid" variable set to only ask for the output for d03. You will then need to use met_em* output for all 3 domains to run real.exe for all 3 domains.

If I knew the domain, could I just save wrfinput and wrfbdy files from real.exe with all three domains? Would I need met_em files?

If you had already run real.exe for all 3 domains, then you will not need to save the met_em* files, as they've already been processed.

Also, I wanted to know which met_em files are mandatory when running a ndown simulation. I read somewhere that for d02 domain end_date could be set as start_date, so just one met_em.d02* would be generated. Is it true? However, if in the future I want to run a d03 domain, should I also execute all met_em files for d02?

As long as you aren't planning to use any sort of nudging options or sst_update = 1 in your wrf simulation, it's okay to set the end date/time to the start date/time in WPS. I believe this should be sufficient to run WRF for ndown, as well, since you'll run everything through real.exe the same as if you were running a two-way nested simulation.