Megan ctsm

[rosiealice]

Description of changes

CTSM side changes to make MEGAN and FATES compatible

Specific notes

Contributors other than yourself, if any:

CTSM Issues Fixed (include github issue #):

Are answers expected to change (and if so in what way)?

Any User Interface Changes (namelist or namelist defaults changes)?

Testing performed, if any:
(List what testing you did to show your changes worked as expected)
(This can be manual testing or running of the different test suites)
(Documentation on system testing is here: https://github.com/ESCOMP/ctsm/wiki/System-Testing-Guide)
(aux_clm on cheyenne for gnu/pgi and hobart for gnu/pgi/nag is the standard for tags on master)

NOTE: Be sure to check your Coding style against the standard:
https://github.com/ESCOMP/ctsm/wiki/CTSM-coding-guidelines

[rosiealice]

Hi all,

So I have a pair of simulations with FATES-SP-MEGAN (this branch) vs CLM6-SP to test the MEGAN outputs.

CLM:
/cluster/work/users/rosief/git/NorESM_alpha07test/cime/scripts/CLM6-SP.n1850.ne30_tn14.megan

FATES:
/cluster/work/users/rosief/git/NorESM_MEGAN_test/cime/scripts/FATES-SP.n1850.ne30_tn14.megan_branch

(this description is pending us deciding on a way to describe and archive the land only simulations which I think we should discuss...)

I ran these for three years from cold start.
The outputs are not the same, but are the same order of magnitude and have the same distribution (pending adding these to the diagnostics package and making real maps @maritsandstad :) ).

We DO NOT expect the answers to be exactly the same here, as FATES will drive MEGAN with different temperature and soil moisture and internal leaf CO2. So a question therefore arises about how different we are OK with these fluxes being? The primary thing I have been thinking about here is how to average the internal CO2 across the whole canopy. At the moment I am using quite a crude method of taking the top leaf layer ci, but I think it might be worth investigating the sensitivity to how this is conducted. There are lots of ways this could be weighted. I will try and test some end members to check them impacts.

NONETHELESS, this is mostly a science tinkering issue. I think the code is fundamentally working and is ready for testing. There are a lot of accumulated variables that drive MEGAN, and so it would be good to see if these are being restarted properly. @mvdebolskiy would it be OK to run this PR through the test suite? (in lieu of me knowing how to do that yet?) Then we will have a sense of what further needs to be done SE-wise.

fOutput plotted per gridcell

![MEG_methanol](https://github.com/user-

Output vs latitude

attachments/assets/6c3fba41-9f68-4006-a062-914f926eafbc)

[mvertens]

@rosiealice - the new test suite has not been in a PR yet - it's still in the issue stage. But I'm happy to kick of a test if you are happy with the test list.