CESM version: CESM2.1.4
Component: CLM (SnowHydrologyMod.F90)
Machine: Olaf (SLURM-based HPC)
Hello,
I encountered an error during model execution where the simulation fails immediately due to negative mass values, specifically in SnowHydrologyMod.F90, as shown below.

To investigate, I first modified the part labeled Adjust water content inside SnowHydrologyMod.F90 to prevent negative values, as shown below.
Original:

After the change:

And then, the error no longer occurred.
To validate the changes, I ran a test simulation (initial 1955~1958) under the same conditions on Aleph (other server system) and compared CESM2 outputs.
After the simulations, I selected variables related to water and snow for comparison.
Some variables (SNOWDP, H2OSNO, QSNOMELT, SALT, SOILWATER, TWS) showed very similar values between them, but the others (SNOW, SSH) are different (I also checked the significant).



So, I was thinking this change might not be correct.
I then found an old CTSM post (Need to increase min_snow_to_keep · Issue #1425 · ESCOMP/CTSM) suggesting to change the value of min_snow_to_keep in SnowHydrologyMod.F90.
So I reverted back to the original SnowHydrologyMod.F90, and only changed the min_snow_to_keep parameter like below.

Unfortunately, the model still fails with the same negative value error.
Given this, I would like to ask:
- Is it acceptable to proceed with CESM2 simulations on Olaf using revised SnowHydrologyMod.F90 below?

- Are there any additional settings or variables we should review to ensure the results are reliable?
- What is the recommended way to handle this negative value error?
I attached config_compilers, config_batch, config_machines files.
Component: CLM (SnowHydrologyMod.F90)
Machine: Olaf (SLURM-based HPC)
Hello,
I encountered an error during model execution where the simulation fails immediately due to negative mass values, specifically in SnowHydrologyMod.F90, as shown below.

To investigate, I first modified the part labeled Adjust water content inside SnowHydrologyMod.F90 to prevent negative values, as shown below.
Original:

After the change:

And then, the error no longer occurred.
To validate the changes, I ran a test simulation (initial 1955~1958) under the same conditions on Aleph (other server system) and compared CESM2 outputs.
After the simulations, I selected variables related to water and snow for comparison.
Some variables (SNOWDP, H2OSNO, QSNOMELT, SALT, SOILWATER, TWS) showed very similar values between them, but the others (SNOW, SSH) are different (I also checked the significant).



So, I was thinking this change might not be correct.
I then found an old CTSM post (Need to increase min_snow_to_keep · Issue #1425 · ESCOMP/CTSM) suggesting to change the value of min_snow_to_keep in SnowHydrologyMod.F90.
So I reverted back to the original SnowHydrologyMod.F90, and only changed the min_snow_to_keep parameter like below.

Unfortunately, the model still fails with the same negative value error.
Given this, I would like to ask:
- Is it acceptable to proceed with CESM2 simulations on Olaf using revised SnowHydrologyMod.F90 below?

- Are there any additional settings or variables we should review to ensure the results are reliable?
- What is the recommended way to handle this negative value error?
I attached config_compilers, config_batch, config_machines files.