noresm3_0_042_cam6_4_121: override CO2 surface source to send to land/ocean by mvertens · Pull Request #294 · NorESMhub/CAM

mvertens · 2026-07-14T13:07:41Z

Summary: New ability to have co2 sent to land/ocean be different than used in radiation/chemistry

Purpose of changes: address ability to run the experiments outlined in NorESMhub/NorESM#825 and #296.

Changes made to build system: None

Changes made to the namelist: New namelist group co2_surface_source_stream_nl
To activate this behavior edit user_nl_clm to have the following:

If you want to send latitude dependent 1850 CO2 forcing to land/ocean:

co2_surface_source = .true.
stream_co2_surface_source_mesh_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/esmf_mesh_20degLon.nc'
stream_co2_surface_source_data_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/ghg_cmip7_CMIP_CR-CMIP-1-0-0_1850_monthly_gnz_0p5degLat_version20260207_20degLon.nc'
stream_co2_surface_source_data_varname = 'CO2_LBC'
stream_co2_surface_source_taxmode = 'cycle'
stream_co2_surface_source_year_first = 1850
stream_co2_surface_source_year_last = 1850
stream_co2_surface_source_year_align = 1

If you want to send 1pct CO2 to land/ocean:

co2_surface_source = .true.
stream_co2_surface_source_mesh_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/esmf_mesh_20degLon.nc'
stream_co2_surface_source_data_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/ghg_cmip7_CMIP-1pctco2_CR-CMIP-1-0-0_0000-0166_monthly_gnz_0p5degLat_version20260207_20degLon.nc
stream_co2_surface_source_data_varname = 'CO2_LBC'
stream_co2_surface_source_taxmode = 'extend'
stream_co2_surface_source_year_first = 0
stream_co2_surface_source_year_last = 166
stream_co2_surface_source_year_align = 1

NOTE: a new namelist was also introduced for nitrogen deposition - stream_ndep_taxmode

Changes to the defaults for the boundary datasets: None

Substantial timing or memory changes: None

Detailed description of changes:
The above custom namelists must be set in user_nl_cam - there are no out of the box defaults.
The 1850 and 1pct CO2 files in $DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/ only had [lat,time] dimensions - and CDEPS cannot work with such files. As a result - 20deg longitude datasets were created for the above scenarios.
Verified that using the following compset 1

1850_CAM70%LT%NORESM%CAMoslo_CLM60%FATES-NCFB%NORESM_CICE_BLOM%HYB%ECO_MOSART_DGLC%NOEVOLVE_
SWAV_SESP

at ne16pg3_tn14 - the co2 diag field sent to the ocean had the expected behavior that was different than the co2 being used internally for the radiation in CAM.

Testing:

All PASS for aux_cam_noresm on Olivia with expected namelist differences and two baseline changes due to fix in ndep namelist defaults

fixes #296

mvertens · 2026-07-14T13:13:45Z

@tjiputra - I think I've implemented the behavior you wanted in NorESMhub/NorESM#825.
Could you please give this a test. I have tested that using the latitude dependent 1850 data (see namelist summary above) gives the latitude dependent data sent to blom - whereas cam is using a global surface mean for the radiation.

tjiputra · 2026-07-15T08:27:44Z

@mvertens - thank you. Should i test this on beta22 or other specific branch?

Using pr-noresm3_0_beta22 branch, I got this error during case.build:
ERROR: in _validate_pair (package Build::NamelistDefinition): Variable name stream_co2_surface_source_year_align not found in /cluster/work/projects/nn9560k/tjiputra/NorESM/NorESM_beta22/components/cam/bld/namelist_files/namelist_definition.xml

mvertens · 2026-07-15T08:42:25Z

@tjiputra - yes - please test this on beta22. However, this code is still in a PR status #294. For you to test this - you need to do the following

> git clone https://github.com/NorESMhub/NorESM
> cd NorESM
> git checkout pr-noresm3_0_beta22

edit .gitmodules to have the following

[submodule "cam"]
path = components/cam
#url = https://github.com/NorESMhub/CAM.git
#fxtag = noresm3_0_039_cam6_4_121
url = https://github.com/mvertens/CAM.git
fxtag = c07bbfc9
fxrequired = ToplevelRequired
fxDONOTUSEurl = https://github.com/NorESMhub/CAM.git

Then you can run the following

> ./bin/git-fleximod update

That should give you the CAM code you need. Please let me know if this is working for you.

tjiputra · 2026-07-15T09:24:23Z

@mvertens -
in user_nl_cam:
stream_co2_surface_source_mesh_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/esmf_mesh_20degLon.nc'
should be:
stream_co2_surface_source_mesh_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/esmf_mesh_20deglon.nc'

But the run crashes:
/cluster/work/projects/nn9560k/tjiputra/noresm/n1pctCO2-BGC.ne16pg3_tn14.beta22.2026-07-15/run/atm.log.1585890.260715-111118

(shr_stream_verifyTCoord) ERROR: calendar dates must be increasing
(shr_stream_verifyTCoord) date(n), date(n+1) = 11216 10116
(shr_stream_verifyTCoord) ERROR: calendar dates must be increasing

Case directory (Olivia):
/cluster/projects/nn9560k/tjiputra/NorESM/cases-noresm3dev/n1pctCO2-BGC.ne16pg3_tn14.beta22.2026-07-15

mvertens · 2026-07-15T09:37:28Z

@tjiputra - I had not tested the 1pctCO2 and I have you the wrong namelist:
can your try the following:

stream_co2_surface_source_year_first = 1
stream_co2_surface_source_year_last = 166
stream_co2_surface_source_year_align = 1

If this does not work - I'll try to duplicate the problem and resolve it.

tjiputra · 2026-07-15T12:04:14Z

@mvertens - the same error occurs again. It seems that it tries to read and cycle the first year even if I set

stream_co2_surface_source_year_first = 0
stream_co2_surface_source_year_last = 166
stream_co2_surface_source_year_align = 0

mvertens · 2026-07-15T12:22:37Z

@tjiputra - that's very odd. I'll track this down. Sorry you ran into this.

mvertens · 2026-07-15T15:06:37Z

@tjiputra - the problem is not in the code - it's in the dataset. I generated a time coordinate for this dataset and it seems to have duplicated the first year:
time = "0001-01-16", // time(1)
"0001-02-15", // time(2)
"0001-03-16", // time(3)
......
"0001-12-16", // time(12)
"0001-01-16", // time(13)
"0001-02-15", // time(14)
"0001-03-16", // time(15)
....
"0001-12-16", // time(24)
The problem was that the dataset started from year 0 - and I wanted to start from year 1. I'll go back to the year0 data and see if that works.

mvertens · 2026-07-15T15:21:38Z

@tjiputra - I have fixed this file on olivia and tested that the following user_nl_cam works:

co2_surface_source = .true.
stream_co2_surface_source_mesh_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/esmf_mesh_20deglon.nc'
stream_co2_surface_source_data_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/ghg_cmip7_CMIP-1pctco2_CR-CMIP-1-0-0_0000-0166_monthly_gnz_0p5degLat_version20260207_20degLon.nc'
stream_co2_surface_source_data_varname = 'CO2_LBC'
stream_co2_surface_source_taxmode = 'extend'
stream_co2_surface_source_year_first = 0
stream_co2_surface_source_year_last = 166
stream_co2_surface_source_year_align = 1

gold2718

I have several clean-up and documentation requests as well as some bug fixes and safety features.

tjiputra · 2026-07-16T06:59:53Z

@mvertens - works and runs well. I will keep this running longer and make sure the behavior of land/ocn/atm is as expected.

Could you also create a stream co2 input file for historical:
/cluster/work/projects/nn9560k/inputdata/atm/waccm/lb/cmip7_ghg_version20260607/ghg_cmip7_CMIP_CR-CMIP-1-0-0_1750-2023_monthly_gnz_0p5degLat_version20260207.nc

Thank you.

mvertens · 2026-07-16T07:46:04Z

@tjiputra - I have created the new dataset - here is the new namelist (assuming you want to start the data at 1850)

co2_surface_source = .true.
stream_co2_surface_source_mesh_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/esmf_mesh_20deglon.nc'
stream_co2_surface_source_data_filename = '$DIN_LOC_ROOT/atm/waccm/lb/cmip7_ghg_version20260607/ghg_cmip7_CMIP_CR-CMIP-1-0-0_1750-2023_monthly_gnz_0p5degLat_version20260207_20degLon.nc'
stream_co2_surface_source_data_varname = 'CO2_LBC'
stream_co2_surface_source_taxmode = 'extend'
stream_co2_surface_source_year_first = 1850
stream_co2_surface_source_year_last = 2023
stream_co2_surface_source_year_align = 1

tjiputra · 2026-07-17T14:15:49Z

@mvertens - Could you correct the the unit of CO2 sent to both land and ocean, which expect [ppm] unit but receive [mol/mol]. Simply multiply them by 1e6.

mvertens · 2026-07-17T14:56:20Z

@tjiputra - thanks for catching this! I'll put the fix in.

mvertens · 2026-07-17T18:54:40Z

@tjiputra - I have fixed the unit conversion and pushed it back to my branch.

tjiputra · 2026-07-19T08:24:10Z

@mvertens - being inexperience with git, how do i get the updated code?
When I did git pull, i got the following message:

remote: Enumerating objects: 5, done.
remote: Counting objects: 100% (5/5), done.
remote: Total 5 (delta 4), reused 5 (delta 4), pack-reused 0 (from 0)
Unpacking objects: 100% (5/5), 540 bytes | 30.00 KiB/s, done.
From https://github.com/NorESMhub/NorESM
424f4be..5d651db pr-noresm3_0_beta22 -> origin/pr-noresm3_0_beta22
Updating 424f4be..5d651db
error: Your local changes to the following files would be overwritten by merge:
.gitmodules
Please commit your changes or stash them before you merge.
Aborting

gold2718 · 2026-07-19T09:35:16Z

@tjiputra

Try this:

git stash
git pull
git stash pop

gold2718

This looks mostly good. I will fix merge conflict and a couple of missing items.

…_surface_source

mvertens · 2026-07-20T15:29:02Z

@tjiputra - if you do a clean checkout of pr-noresm3_0_beta22 you should get this tag.

mvertens added 5 commits July 13, 2026 10:18

added new co2 surface source to overwrite co2_diag

5bb1dc9

fixed compiler problems

e09687d

updates to get 1850 test case working

0b96e55

added taxmode as namelists to both ndep and co2 streams

cba4505

changes to get tests for co2_surface_source working

c07bbfc

mvertens requested review from gold2718 and tjiputra July 14, 2026 13:10

mvertens changed the title ~~Feature/co2 surface source~~ override co2 surface source to send to land/ocean Jul 14, 2026

gold2718 requested changes Jul 15, 2026

View reviewed changes

addressed issue raised in PR review

e1dcbb0

mvertens requested a review from gold2718 July 16, 2026 07:26

now sending ppm rather than mmol co2 to land/ocean

62c1b5d

gold2718 self-assigned this Jul 19, 2026

gold2718 added this to NorESM Development Jul 19, 2026

github-project-automation Bot moved this to Todo in NorESM Development Jul 19, 2026

gold2718 added the enhancement New feature or request label Jul 19, 2026

github-project-automation Bot moved this from Todo to In Progress in NorESM Development Jul 19, 2026

gold2718 added this to the noresm3_0_beta22 milestone Jul 19, 2026

gold2718 approved these changes Jul 19, 2026

View reviewed changes

Steve Goldhaber added 3 commits July 19, 2026 21:33

Merge remote-tracking branch 'NorESM/noresm_develop' into feature/co2…

acc3c36

…_surface_source

Fix character declarations and init logic

63e0f35

Fix logic bug introduced by following reviewer change request

550f2e2

gold2718 merged commit ed80c85 into NorESMhub:noresm_develop Jul 20, 2026
2 checks passed

github-project-automation Bot moved this from In Progress to Done in NorESM Development Jul 20, 2026

gold2718 changed the title ~~override co2 surface source to send to land/ocean~~ noresm3_0_042_cam6_4_121: override co2 surface source to send to land/ocean Jul 20, 2026

gold2718 changed the title ~~noresm3_0_042_cam6_4_121: override co2 surface source to send to land/ocean~~ noresm3_0_042_cam6_4_121: override CO2 surface source to send to land/ocean Jul 20, 2026

gold2718 mentioned this pull request Jul 20, 2026

Add ability to send LBC CO2 directly to surface #296

Closed

tjiputra mentioned this pull request Jul 21, 2026

Issue with atmospheric CO2 concentration received by ocean NorESMhub/NorESM#830

Open

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