Negative SIF value from the CLM SourceMods

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Describe the bug

This is not a bug in DART. This is a bug in the SourceMods of CLM SIF module. Just would like to mention here in case the SIF SourceMods will be included in the future DART versions.

I ran CLM with the SIF SourceMods. It was an 80-ensemble free run without assimilating any observations. The simulation period is from 2003 to 2010. SIF should always be positive. However, a negative SIF value occurred in April 2005.

Error Message

CLM didn't blow up. Instead, it continued running until the end of the simulation period, though the negative SIF doesn't make sense.

Which model(s) are you working with?

CLM with the SIF module developed by Li et al 2022 (https://doi.org/10.1029/2021MS002747 https://github.com/ESCOMP/CTSM/issues/1672) in SourceModes.
The version of CLM is release-cesm2.2.01

Screenshots

The negative SIF occurred in the PFT (with vegetation type as 10) within the grid cell indexed with (9,11) (latidx, lonidx) at one time step on the simulation date 2005-04-28 in ensemble member 37.

Version of DART

Which version of DART are you using?
You can find the version using git describe --tags
v10.7.0-111-g70e6af803

Have you modified the DART code?

No
If your code changes are available on GitHub, please provide the repository.

Build information

Please describe:

1. The machine you are running on (e.g. windows laptop, NSF NCAR supercomputer Derecho).
   CHPC university of utah.
2. The compiler you are using (e.g. gnu, intel).
   Intel

Start by examining the CLM SIF SourceMods used with CLM release-cesm2.2.01, focusing on the reported PFT 10 at grid indices (9,11) on 2005-04-28 in ensemble member 37. Reproduce or trace that case to determine whether the negative SIF originates in the SourceMods; done means identifying a confirmed cause or documenting that it is outside DART.