Standard names: surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes_including_total_riverine_carbon_export_to_ocean

[ckoven]

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Please note that it is fine to group together a number of proposals in a single GitHub issue (i.e. it is not necessary to open a separate issue for each vocabulary term). Change proposals should include the following information as applicable.

Proposer's name Charlie Koven

Date Apr. 7, 2026

For each term please try to give the following:

- Term surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes_including_total_riverine_carbon_export_to_ocean

- Description Flux of carbon from the atmosphere to the land surface due to all land processes as well as riverine carbon exported from the land to the ocean. "All land processes" means plant and soil respiration, photosynthesis, animal grazing, crop harvesting, natural fires and anthropogenic land use change. "Anthropogenic land use change" means human changes to land, excluding forest regrowth. It includes fires ignited by humans for the purpose of land use change and the processes of eventual disposal and decomposition of wood products such as paper, cardboard, furniture and timber for construction. "Riverine carbon export to the ocean" means dissolved or particulate carbon transported from land ecosystems via rivers to the ocean.

- Units kg m-2 s-1

[github-actions]

Thank you for your proposal. These terms will be added to the cfeditor (http://cfeditor.ceda.ac.uk/proposals/1) shortly. Your proposal will then be reviewed and commented on by the community and Standard Names moderator.

[JonathanGregory]

Dear Charlie @ckoven

Thanks for your proposal. I am a puzzled by it being called a surface flux if it includes riverine export, since that's not a flux between land surface and atmosphere. I wonder whether the idea is the rate of change of the mass of carbon per unit area on land due to all land processes, expressed as a CO2 flux, perhaps?

Best wishes

Jonathan

[japamment]

Dear Charlie @ckoven

Many thanks for your proposal which I have now entered into the CF editor: https://cfeditor.ceda.ac.uk/proposal/5824/.

Like Jonathan, I am wondering if this is truly a surface flux if it includes the riverine transport and I think this does sound more like a net flux into land areas. (In CF, a surface flux would usually have only an upward or downward direction, and net downward would mean the difference between the downward and upward fluxes at a given location).

We have a number of existing names for fluxes into or out of a medium, e.g. mass_flux_of_carbon_into_litter_from_vegetation and mass_flux_of_carbon_out_of_soil_due_to_leaching_and_runoff. Among these is the name mass_flux_of_carbon_into_sea_water_from_rivers which I think would be the same as the total_riverine_carbon_export_to_ocean part of the quantity you are proposing so we could use that wording for consistency.

We also already have the name surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes.

Combining the two existing names, perhaps the new name could be written as net_mass_flux_of_carbon_into_land_from_surface_net_downward_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes_and_flux_of_carbon_into_sea_water_from_rivers
(N.B. I removed repetition of the word mass since it appears at the start of the name). This is rather long, but I think it does describe the quantity and using and to join phrases in standard names is fine. What do you think?

Best wishes,
Alison

[taylor13]

how about a construct along the lines of tendency_of_soil_mass_content_of_carbon?

[japamment]

Hi Karl, @taylor13

Yes, I agree that would work. So we could have
tendency_of_land_mass_content_of_carbon_from_surface_net_downward_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes_and_flux_of_carbon_into_sea_water_from_rivers and units of kg m-2 s-1 would still be consistent. @ckoven would you be okay with this version?

Best wishes,
Alison

[taylor13]

Or I think we could drop the "due to...." if the list includes all fluxes into the soil column (horizontally and at the surface), couldn't we?

[JonathanGregory]

I agree. If this is all processes which modify the land carbon mass content, it shouldn't have due_to in it, following our usual pattern that the unqualified default means everything.

[taylor13]

just notice in #306 (comment), it's not "due to ..." but "from ..." that I think should be dropped.

[ckoven]

Hi All--Thanks for this feedback. From my perspective, I believe this is still a surface flux, but let me explain my thinking and see if you agree. The directionality of the flux here is that carbon flows along the following pathway: atm -> land -> rivers -> ocean. I.e. rivers effectively form a bottom boundary to the land carbon cycle, in that drainage out of soils is the input flux to rivers, and all carbon that goes to rivers must first pass through the land-atmosphere boundary. So the intention of this proposed variable here is to distinguish from the net flux surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes, which corresponds to the CMIP variable nbp, and which should integrate in time to be the change in terrestrial carbon stocks, from what the atmosphere actually sees in terms of land fluxes in models that include a nonzero land-river-ocean carbon flux, which doesn't integrate in time to a change in land carbon stocks, because of the open-ended bottom boundary condition from the land to rivers, (and so I don't believe that that would make it a mass tendency).

So the goal here is to capture the surface flux over land, but which also accounts for the fact that models may have a land that leaches carbon out of soils into rivers and the ocean. It isn't actually flowing into or out of a soil or vegetation or river pool, it is the net flux at the surface that is the sum of all of these things.

[japamment]

Dear Charlie, Karl and Jonathan,

Thank you all for your comments.

Many thanks for your clarification, Charlie. I think I see now that you are indeed interested in a surface flux at the bottom of the atmosphere which is surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes, plus an additional term in which carbon is removed from the land by hydrological processes and is therefore not available to be re-released to the atmosphere (so would actually increase the value of surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes). Is that right?

If so, then I do agree that we should address this with a surface_flux standard name, but perhaps we don't need to specify that the final destination of the runoff carbon is the ocean via rivers. Instead, we could think of it as some combination of the two existing names surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes and mass_flux_of_carbon_out_of_soil_due_to_leaching_and_runoff.

The description of the latter is 'In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. "Leaching" means the loss of water soluble chemical species from soil. Runoff is the liquid water which drains from land. If not specified, "runoff" refers to the sum of surface runoff and subsurface drainage.'

Based on this, I'd now suggest the new name could be the following:
surface_net_downward_mass_flux_of_carbon_dioxide_expressed_as_carbon_due_to_all_land_processes_and_soil_loss_of_carbon_due_to_leaching_and_runoff

We could base the description on the explanation above and the text for the two existing names:
'This quantity is the flux of carbon from the atmosphere to the land surface due to all land processes, plus an additional term in which carbon is leached from the land and is therefore not available to be re-released to the atmosphere. The surface called "surface" means the lower boundary of the atmosphere. "Downward" indicates a vector component which is positive when directed downward (negative upward). In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. The phrase 'expressed_as' is used in the construction A_expressed_as_B, where B is a chemical constituent of A. It means that the quantity indicated by the standard name is calculated solely with respect to the B contained in A, neglecting all other chemical constituents of A. "All land processes" means plant and soil respiration, photosynthesis, animal grazing, crop harvesting, natural fires and anthropogenic land use change. "Anthropogenic land use change" means human changes to land, excluding forest regrowth. It includes fires ignited by humans for the purpose of land use change and the processes of eventual disposal and decomposition of wood products such as paper, cardboard, furniture and timber for construction. "Leaching" means the loss of water soluble chemical species from soil. Runoff is the liquid water which drains from land. If not specified, "runoff" refers to the sum of surface runoff and subsurface drainage. The chemical formula for carbon dioxide is CO2.'

This is still quite a lengthy name and description, but are we getting closer to what is needed?

Best wishes,
Alison