Allow for SE tracer transport of water vapor when running CSLAM

[adamrher]

What is the feature/what would you like to discuss?

Prior to PR https://github.com/ESCOMP/CAM/pull/968/, tracers were advected by both CSLAM and the SE tracer transport scheme when running CSLAM configurations -- the CSLAM tracer values would then overwrite the SE tracer values at the end of the time-step. In the PR linked above we turned off the advection by SE tracer transport, which sped up the model considerably. However, I noticed in an FKESSLER run that this creates a significant amount of noise in the solution:

Where CAM = cam6_4_007, and CAM-SIMA uses an older version of SE that predates the PR.

Peter and I were thinking that we could revert the PR https://github.com/ESCOMP/CAM/pull/968 for water vapor only -- that PR turned off SE transport of all tracers -- as that should alleviate the noise seen in the baroclinic wave.

Is there anyone in particular you want to be part of this conversation?

@PeterHjortLauritzen has agreed to implement these code mods.

Will this change (regression test) answers?

Yes

Will you be implementing this enhancement yourself?

No