NLDAS-2 to create forcing

[tslin2]

The following is copied from communications between a user and our Noah-MP technical team regarding generating NLDAS-2 atmospheric forcing, which may be useful for other users in the community.

Q: I am trying to use NLDAS-2 to create forcing at different spatial scales over the texas region.
I tried using the GEOGRID.TBL.ARW and the GEOGRID.TBL.ARW.noahmp to create my geo_em.d0x.nc files.

./create_forcing.exe can be executed at a fine spatial resolution (1_km, geo_em.d03.nc) however when I use geo_em.d01.nc and geo_em.d02.nc, I am getting the error below. I tried modifying the expand_loop with no luck. I was wondering if you have any recommendations on what to do next.

I have three spatial resolutions 1km, 3km, and 9 km. Would it help if I made them coarser?

I am using the same GEOGRID.TBL for all domains.
The finer resolution domain is not causing any problems when it comes to ./create_forcing.exe, however I am getting those issues for the coarser resolution.
I tried a wide variety of expand_loop values (1-100) but the error message did not show any sensitivity to these changes.
Also, I tried to change the expand_loop value to 200 and the error message is still insensitive to that.

Do you think that the small spacing between the inner and outer domains will cause any problems when I am running ./hrldas.exe?

Thank you

Error Message:
You have this many undefined T points over valid land points: 1081
This tends to happen around coastlines or for unresolved islands in your forcing data
===== Consider increasing expand_loop in namelist =====
However, this may also occur if your forcing source does not cover your domain.

[tslin2]

Your WPS domain has parts of grid cells outside the NLDAS-2 climate coverage (25-53 North).
The longitude of domain 3 is above 25 degree north, so it did not have any issues while generating forcing files.
Please try to change your domain inside the NLDAS2 climate coverage.

To answer your question, the small spacing between the inner and outer domains cannot cause any problems while running ./hrldas.exe as it does not have feedback between domains. However if you plan to run WRF, this may create the issue and also is not the efficient way to run WRF. Normally, 4 grid cells are required for community between parent and nested domains, and it is good to have ~1/3 of coarse-grid surrounding each side of the nest (see slide 22 of the WRF tutorial, https://www2.mmm.ucar.edu/wrf/users/tutorial/presentation_pdfs/202101/werner_nesting.pdf)