The distinct “line” in high-resolution CLM simulations

[hm.xiao]

What version of the code are you using?
We use the CLM51 (Compset: 2000_DATM%1PT_CLM51%BGC_SICE_SOCN_SROF_SGLC_SWAV_SESP)

Have you made any changes to files in the source tree?
We use high-resolution atmospheric forcing (2 km) to drive a high-resolution regional CLM simulation (2 km). For this simulation, we initially used the 0.05-degree land-surface dataset downloaded from the NCAR website. Later on, we replaced land-surface data with another set of high-resolution land-surface datasets (2km).


Describe every step you took leading up to the problem:
The model outputs related to carbon (such as CWDC) show a distinct “line” between certain regions (indicated by the black vector in the attached picture), whereas the other variables (such as soil temperature and moisture) appear reasonable. This distinct “line” persists even after we increased the resolution of the land-surface datasets.

Describe your problem or question:
Is this problem related to default parameters that may be tied to coarse-resolution in CLM? How should we fix this problem?

Thanks!

 

[slevis]

Troubleshooting ideas:
- Try looking for this "line" in the inputs, such as in surface dataset fields (of the fsurdat file).
- If that doesn't help, look for the line in all the history fields and try to figure out what they have in common.
- Are you possibly initializing the high resolution case with a finidat/restart file from the low resolution case and could that explain this behavior?

 

[hm.xiao]

Thanks, Slevis!
We checked point 1 and point 2 and found no direct relationship. The “line” also appears consistently across all timesteps.
After removing the initial files (your point 3), we found that the line disappears when using a cold start.
Running several hundred years at 2 km resolution would require substantial computational resources, we decided to run a 10 km regional simulation first and then use its restart file to drive the 2 km regional simulations. With this approach, the "line" no longer appears.