GEOS-Chem v14.4, Cloud-J photolysis, and HETP aerosol thermodynamics

[lizziel]

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

I have an existing PR under review that brings GEOS-Chem chemistry into CAM as an alternative to CAM-Chem (#484). That PR uses GEOS-Chem v14.1 released in February 2023. I am now working on GEOS-Chem v14.3 in CAM that can be merged in after my existing PR is merged. It is a relatively simple update, though still in progress. However, it requires an update to HEMCO and also brings in a new external, Cloud-J, that is a replacement for legacy Fast-JX previously hard-coded in GEOS-Chem to compute J-values. Besides use in GEOS-Chem, we are in discussion with NCAR about using Cloud-J as an option within CAM-Chem and including it in MUSICA.

I would like your feedback on order of bringing in these updates. In theory I could update my current PR to use 14.3 and include Cloud-J. However, it is so far along and near merge I am hesitant to change it. Plus we have published papers that use GEOS-Chem 14.1 in CESM and it would be nice to have a tag for that version. Assuming GEOS-Chem v14.3 and Cloud-J come in as a later PR I could either bundle them together or submit as separate PRs. Do you have a preference?

Ideally this would go into CESM3.0 if possible. There will be no changes in outputs except when running with GEOS-Chem chemistry.

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

@cacraigucar @jimmielin

Will this change (regression test) answers?

I do not think there are changes in HEMCO that would affect results for non-GEOS-Chem runs. However, I would need to check on that.

Will you be implementing this enhancement yourself?

Yes

[cacraigucar]

@lizziel - I advise you to have #484 go in as it currently stands. Any modifications (other than addressing reviewer comments) will slow the tag down completely. It is appropriate to open a a new PR with the additional mods that are wanted.

[lizziel]

@cacraigucar, yes, I agree. Do you think it is feasible to target CESM3.0 for the version update and inclusion of Cloud-J? We have a GEOS-Chem conference in early June and it would be wonderful to announce its inclusion in CESM at the meeting.

[cacraigucar]

@lizziel - I can't answer on the feasibility right now. Once the PR is open and we can see the scope of the changes we can give you a better answer. It would also need an approval from the NCAR ACOM group that they believe these changes should come in.

[lizziel]

The PR accompanying this issue is now ready for review at #1093. Since this issue was opened GEOS-Chem was brought into the cam_development branch. The new PR features GEOS-Chem 14.4 (originally I was aiming for 14.3 but enough time has passed that we have a newer version). It also include Cloud-J photolysis (new in 14.3) and HETP aerosol thermodynamics as an improvement upon ISORROPIA (new in 14.4).