bring soil NOx scheme into CTSM

[mvalmartin]

We would like to bring a soil NOx parameterization into CTSM. This issue is requested by Louisa Emmons, Anthony Wong and @mvalmartin. The code is in Cheyenne, implemented in CESM2.1 with release-clm5.0.25.
May you please advise on what is needed by the CTSM team at this stage?
Thanks!
Maria

[wwieder]

It would be helpful to have some idea what approach you've taken for this. Seems like you have a paper in prep, which is helpful (and I need to look at!). Beyond a broader scientific description of what you're trying to do (which you can add to this issue).

You should also open up a pull request to bring the code to the main development branch of CTSM. It would be most productive if your team can work on bringing your code up to the main CTSM5.1 dev118 code base. We the LMWG software team, can help advise on this, but likely don't have a lot of time to spend on this in the short term. Having a planning meeting to help scope this out would be productive once you open a PR.

Finally, what is your timeline for having this code integrated into CTSM, specifically, is CAM-Chem hoping to have this for CESM3?

[mvalmartin]

Hi Will, Thanks for getting back to me!

The idea is to bring the soil NOx scheme into ctsm to use it with CAM-chem and have it ready for CESM3. I'm tagging Louisa Emmons (@lkemmons) here as she can follow-up about that too.

We could do it in a more simple way that in my GMD draft manuscript, eg independently of soil pH, that is, using the fixed soil pH of 6.5 and leaving soil NH3 out. It is not a massive implementation if we leave NH3 and all the weathering modules out. The scheme follows DayCent (Parton et al 2001) and uses the current N2O denitrification and nitrification schemes.

I don't think that adding the code in CTSM5.1 dev118 code base will be a massive job, I can try to do it, test and evaluate it. Now, the only catch is the coupling (land to atm). I remember trying to couple the scheme in cesm2.2 and gave up as the structure had substantially changed from cesm2.1 (where I had already coupled the soil NOx and NH3 from clm5 to cam-chem). Could the LMWG software team advise on that?

Thanks again!

Maria

[ekluzek]

@mvalmartin yes we should talk about sending this through CMEPS from CAM to CTSM. I assume this would be something would be turned on some of the time -- but not ALL of the time right?

We should probably add it as a namelist to drv_flds_in with at least a logical variable to say it's turned on or not. That can be seen by both CTSM and CAM to know it's being passed.

[mvalmartin]

Yes! What we need is to pass soil NOx from CTSM to CAM. I already have a namelist in my version, with a switch (use_soil_emis=true or false). However, I couldn't manage to implement it in cesm2.2, hence I am still working with cesm2.1 and clm5.0.25.

I will start transfering the soil NOx code into ctsm5.1.

When is the code going to be frozen for cesm3? That will help me get organized here!

Thanks!

[ekluzek]

@mvalmartin there's not a fixed date for CESM3 to be frozen yet. But, the first coupled experiments with updated components are ongoing now. There's talk of CMIP7 experiments starting mid 2024, and I think the desire is for most updates for CESM3 to be in the models by this Summer. As such we'd like to see a PR for this right away if possible. You can start a branch and get the PR started as a draft, but describe it as a Work In Progress. It helps for us to start to see the changes and know the branch exists and can be brought in. That also helps in us reviewing the code and working with you on changes needed.

This is more than you need but these are slides from Gokhan about the current planning on all of this.
cesm_cochairs_20230228.pptx

[wwieder]

Thanks for posting on this, @ekluzek . To confirm, our current plan is to start CMIP7 simulations with CESM3 in the summer of 2024. This timeline is highly dependent on external forcing data from the CMIP community as well as a stable model code that WGs are satisfied with, but it's the most firm info we've had to date.

[mvalmartin]

Thanks @wwieder and @ekluzek for getting back to me. I should be able to transfer the soil NOx scheme into the CTSM5.1 in the next weeks. (now that I submitted the manuscript!).