Standard names: Propose new names for trace gases and aerosols for use in AerChemMIP2 and CMIP7

[fmoconnor]

On behalf of the Aerosol and Chemistry Model Intercomparison Project for CMIP7, I would like to propose standard names for a number of variables for which no standard name currently exists. These are as follows:

Name: atmosphere_absorption_optical_thickness_due_to_nitrate_ambient_aerosol_particles Units: 1 Metadata: The optical thickness is the integral along the path of radiation of a volume scattering/absorption/attenuation coefficient. The radiative flux is reduced by a factor exp(-optical_thickness) on traversing the path. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the optical thickness applies at specific wavelengths or frequencies. "Absorption optical thickness" means that part of the atmosphere optical thickness that is caused by the absorption of incident radiation. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. "Ambient_aerosol" means that the aerosol is measured or modelled at the ambient state of pressure, temperature and relative humidity that exists in its immediate environment. "Ambient aerosol particles" are aerosol particles that have taken up ambient water through hygroscopic growth. The extent of hygroscopic growth depends on the relative humidity and the composition of the particles. To specify the relative humidity and temperature at which the quantity described by the standard name applies, provide scalar coordinate variables with standard names of "relative_humidity" and "air_temperature". 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.

Name: tendency_of_atmosphere_mole_concentration_of_oh_due_to_chemical_production_from_O1D+H2O Units: mol m-3 s-1 Metadata: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical production" means the result of all chemical reactions within the medium (here, atmosphere) that produce a certain amount of a particular species from the medium. The chemical formula for hydroxyl is OH.

Name: surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes Units: kg m-2 s-1 Metadata: The surface called "surface" means the lower boundary of the atmosphere. "Upward" indicates a vector component which is positive when directed upward (negative downward). In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. The chemical formula for methane is CH4. The mass is the total mass of the molecules. The phrase "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Emission" means emission from a primary source located anywhere within the atmosphere, including at the lower boundary (i.e. the surface of the earth). "Emission" is a process entirely distinct from "re-emission" which is used in some standard names.

Name: tendency_of_atmosphere_moles_of_methane_due_to_chemical_destruction_by_hydroxyl Units: mol m-3 s-1 Metadata: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical destruction" means the result of all chemical reactions within the medium (here, atmosphere) that destroy a certain amount of a particular species from the medium. The chemical formula for methane is CH4. The chemical formula for hydroxyl is OH.

Name: surface_downward_mass_flux_of_methane_due_to_soil_biological_consumption Units: kg m-2 s-1 Metadata: 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 chemical formula for methane is CH4. The mass is the total mass of the molecules. The specification of a physical process by the phrase "dueto" 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.

Name: tendency_of_atmosphere_mole_concentration_of_ozone_due_to_net_chemical_production Units: mol m-3 s-1 Metadata: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Net Chemical production" means the result of "Chemical Production" minus "Chemical Destruction". "Chemical Production" refers to all chemical reactions within the medium (here, atmosphere) that produce a certain amount of a particular species from the medium. "Chemical Destruction" is the result of all chemical reactions within the medium (here, atmosphere) that destroy a certain amount of a particular species. The chemical formula for ozone is O3. The IUPAC name for ozone is trioxygen.

Name: tendency_of_atmosphere_moles_of_molecular_hydrogen_due_to_chemical_production Units: mol m-3 s-1 Metadata: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical Production" refers to all chemical reactions within the medium (here, atmosphere) that produce a certain amount of a particular species from the medium. The chemical formula for molecular hydrogen is H2.

Name: tendency_of_atmosphere_moles_of_molecular_hydrogen_due_to_chemical_destruction Units: mol m-3 s-1 Metadata: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical Destruction" refers to all chemical reactions within the medium (here, atmosphere) that destroys a certain amount of a particular species from the medium.

Thank you for considering our proposal.

Proposer's Name: Fiona O'Connor Date: 29 August 2024

[github-actions[bot]]

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.

[fmoconnor]

Three more to add, if that's okay:

Name: number_concentration_of_cloud_condensation_nuclei_at_0.2_percent_supersaturation_in_air Units: m-3 Metadata: "Number concentration" means the number of particles or other specified objects per unit volume. The cloud condensation nuclei number concentration is the total number of aerosol particles per unit volume independent of and integrated over particle size that act as condensation nuclei for liquid-phase clouds. A coordinate variable with the standard name of relative_humidity should be specified to indicate that the property refers to a specific supersaturation of 0.2 percent with respect to liquid water. The ability of a particle to act as a condensation nucleus is determined by its size, chemical composition, and morphology.

Name: number_concentration_of_cloud_condensation_nuclei_at_1_percent_supersaturation_in_air Units: m-3 Metadata: "Number concentration" means the number of particles or other specified objects per unit volume. The cloud condensation nuclei number concentration is the total number of aerosol particles per unit volume independent of and integrated over particle size that act as condensation nuclei for liquid-phase clouds. A coordinate variable with the standard name of relative_humidity should be specified to indicate that the property refers to a specific supersaturation of 1 percent with respect to liquid water. The ability of a particle to act as a condensation nucleus is determined by its size, chemical composition, and morphology.

Name: tendency_of_atmosphere_mass_content_of_ammonium_dry_aerosol_particles_due_to_net_chemical_production Units: kg m-2 s-1 Metadata: "Content" indicates a quantity per unit area. The "atmosphere content" of a quantity refers to the vertical integral from the surface to the top of the atmosphere. For the content between specified levels in the atmosphere, standard names including "content_of_atmosphere_layer" are used. The mass is the total mass of the particles. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. Aerosol particles take up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the particles. "Dry aerosol particles" means aerosol particles without any water uptake. The specification of a physical process by the phrase "dueto" 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. "Net chemical production" means the net result of all chemical reactions within the atmosphere that produce or destroy a particular species. "tendency_of_X" means derivative of X with respect to time. The chemical formula for the ammonium cation is NH4+.

[efisher008]

Hi Fiona @fmoconnor,

Thank you for your patience. I have now added your proposed names into the CF editor.

I can see a potential issue with the name tendency_of_atmosphere_mole_concentration_of_oh_due_to_chemical_production_from_O1D+H2O, as standard names do not generally contain symbols other than underscores (please see the discussion/explanation in this issue). I don't believe we have any names in the current table with a + symbol, this may be worth exploring but I would refer to @japamment or another member of the conventions/standard names committee would be able to comment.

Your number_concentration names look fine. We have two existing names with number_concentration and cloud_condensation_nuclei in their construction: these are number_concentration_of_cloud_condensation_nuclei_in_air and number_concentration_of_cloud_condensation_nuclei_at_stp_in_air. As it looks like you have used elements of the description of these names in the newly proposed ones, these should be straightfoward to accept.

I will update again on this soon, but in the meantime if you have any further comments or questions feel free to add to the issue.

Best wishes, Ellie

[taylor13]

Is there some way the at_X_percent_supersaturation could be indicated outside the standard name? Perhaps a scalar coordinate or following the "threshold" approach used in some standard names. If X could be any value among dozens (or perhaps an uncountable number) of values, we'd like to avoid proliferation of standard names to account for all the values.

[taylor13]

Also, I wonder if _oh_ should be replaced with _OH_ or perhaps _hydroxyl_radical_.

[martinjuckes]

I support Karl's suggestion. We have 8 existing names referring to _hydroxyl_radical_ and none for _oh_

[fmoconnor]

@efisher008 @taylor13 @martinjuckes Thanks for your comments on the proposed standard name tendency_of_atmosphere_mole_concentration_of_oh_due_to_chemical_production_from_O1D+H2O. I agree with the suggestion to replace oh with hydroxyl_radical - this would make the name consistent with other standard names involving oh. In relation to the O1D+H2O part of the name, how about O1D_and_H2O?

Another possibility is O1D_and_H2O_reaction.

[fmoconnor]

In response to comments by @taylor13 on the proposed names number_concentration_of_cloud_condensation_nuclei_at_0.2_percent_supersaturation_in_air and number_concentration_of_cloud_condensation_nuclei_at_1_percent_supersaturation_in_air, I agree that such names open up the possibility for proliferation and are best avoided. In this case, we could make use of the existing CF name number_concentration_of_cloud_condensation_nuclei_in_air, the metadata for which suggests that a coordinate variable with the standard name of relative_humidity be specified to indicate that the property refers to a specific supersaturation with respect to liquid water. This covers what we want!

If there's agreement, I then suggest to remove the proposed names number_concentration_of_cloud_condensation_nuclei_at_0.2_percent_supersaturation_in_air and number_concentration_of_cloud_condensation_nuclei_at_1_percent_supersaturation_in_air from this issue.

[martinjuckes]

@fmoconnor : thanks for tackling the challenge of getting these concepts into CF.

How about: tendency_of_atmosphere_mole_concentration_of_hydroxyl_radical_due_to_chemical_production_from_singlet_d_oxygen_and_water_vapour

These may be naive questions, but is 1 percent supersaturation the same as 101% relative humidity? Does it matter whether you are concerned about supersaturation over ice or water?

[JonathanGregory]

A small point: we use the American spelling of vapor.

[fmoconnor]

@martinjuckes @JonathanGregory thanks both for your comments. I've just found that there exists the standard name photolysis_rate_of_ozone_to_1D_oxygen_atom so, given both of your comments, how about tendency_of_atmosphere_mole_concentration_of_hydroxyl_radical_due_to_chemical_production_from_1D_oxygen_atom_and_water_vapor?

[fmoconnor]

@martinjuckes thanks for the questions on 1 percent supersaturation. Not naive at all. Just following up with the relevant community before I get back to you. Hope that's okay!

[JonathanGregory]

Dear both

I wasn't aware of photolysis_rate_of_ozone_to_1D_oxygen_atom either. That's the only atom in the standard name table, I see, but there are lots of atomic_element phrases. Coming to this phrase from a state of ignorance, I was puzzled by 1D_oxygen_atom. The only thing that occurred to me was "one-dimensional". :smiley: To make it more obvious in words would need something like "atomic oxygen in excited state 1D", but that's rather long.

If words are too long maybe we could after all use the symbol? We don't use chemical formulae for unexcited elements of natural composition or for compounds, but we do use atomic symbols for isotopes e.g. 13C. Perhaps the symbol would be clearer than words. To write the symbol O(1D) clearly we would also need parentheses, which would be unprecedented for standard names, but might be necessary, given that D also means deuterium, doesn't it?

Best wishes

Jonathan

[martinjuckes]

Dear Both,

On reflection, my suggestion of _oxygen_atom_and_water_vapour creates a rather odd combination of a single atom with a gas.

How about _singlet_oxygen_1D, _atomic_oxygen_singlet1D_ or _Os1D_? We have, for instance, 113mAg for a metastable isotope of silver.

[JonathanGregory]

If I understand what I've just read correctly, the "1" means "singlet", so we needn't say both. Google finds that the phrase "atomic singlet oxygen" is used in the literature for "O(¹D)". Could we say tendency_of_atmosphere_mole_concentration_of_hydroxyl_radical_due_to_chemical_production_from_atomic_singlet_oxygen_and_water_vapor?

[fmoconnor]

Both, we typically refer to "O1D" as "O one D" or "O singlet D" or as an "excited singlet oxygen atom". So, I'm not sure that I like the suggestions of _singlet_oxygen_1D, _atomic_oxygen_singlet1D_ or _Os1D_ because of exactly what @JonathanGregory says above (while I'm still typing). How about either 1D_oxygen_atom (because it is consistent with photolysis_rate_of_ozone_to_1D_oxygen_atom even if the 1D is potentially confusing and could be interpreted as "one-dimensional") or simply O1D without any brackets or excited_singlet_oxygen_atom or atomic_singlet_oxygen (as suggested above)?

[JonathanGregory]

If you think atomic_singlet_oxygen conveys the correct meaning for you, I think it would be adequate for someone like me who isn't familiar with these species. atomic_oxygen alone would be consistent with other standard names e.g we have atmosphere_mass_content_of_atomic_nitrogen. The singlet signals that it is something "special". Until I looked it up this afternoon, I didn't know that O(¹D) is the first excited state. Therefore excited_singlet_atomic_oxygen would be more informative.

[JonathanGregory]

We can, and probably we should, change photolysis_rate_of_ozone_to_1D_oxygen_atom, using an alias, to be consistent with whatever we decide in this case. As I noted above, that's the only standard name that has element_atom rather than atomic_element.

[martinjuckes]

Both singlet_atomic_oxygen and excited_singlet_atomic_oxygen look good to me. I have a slight preference for the first because excited is redundant and might make people wonder what the unexcited_singlet_atomic_oxygen looks like.

[fmoconnor]

Thanks both :) I'm going to check with my chemist friends and get back to you!

[fmoconnor]

@martinjuckes @JonathanGregory Having consulted with my chemist friends, we would like to propose tendency_of_atmosphere_mole_concentration_of_hydroxyl_radical_due_to_chemical_production_from_atomic_singlet_oxygen_and_water_vapor.

Also, the reaction of O1D with H2O generates 2 hydroxyl (OH) radicals, i.e., O1D+H2O -> 2OH. They also suggested that we add some additional text to the metadata to be explicit that we want the diagnostic to take account of the factor of 2. Also, some older models may not include O1D, and may represent the production of OH differently (but with O1D implicit) - I'm going to propose some additional text to cover that case too.

Here's my suggested update to the metadata: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical production" means the result of all chemical reactions within the medium (here, atmosphere) that produce a certain amount of a particular species from the medium. The chemical formula for hydroxyl is OH. The chemical formula for atomic_singlet_oxygen is O1D. The chemical formula for water vapor is H2O. Here, the production of hydroxyl radical is equal to 2k[O1D][H2O], i.e., 2 hydroxyl radicals are formed from the reaction of O1D with H2O. For models that do not have O1D as a species, the production of hydroxyl radical may be represented differently but the chemical production should take account of the hydroxyl yield.

[JonathanGregory]

That seems fine to me, @fmoconnor. I think the tendency of the mole concentration certainly refers to the rate at which hydroxyl is produced, not the rate at which the reactants are consumed, but there is no harm in spelling it out, as you have. Thanks.

[efisher008]

Hi Fiona @fmoconnor,

I have updated the original name tendency_of_atmosphere_mole_concentration_of_oh_due_to_chemical_production_from_O1D+H2O to tendency_of_atmosphere_mole_concentration_of_hydroxyl_radical_due_to_chemical_production_from_atomic_singlet_oxygen_and_water_vapor and replaced the description with the amended text as per your post.

Did you manage to check with your colleagues regarding the supersaturation names and @martinjuckes question? As a reminder, these were: number_concentration_of_cloud_condensation_nuclei_at_0.2_percent_supersaturation_in_air number_concentration_of_cloud_condensation_nuclei_at_1_percent_supersaturation_in_air

Best regards, Ellie

[tommibergman]

I am part of a separate discussion on cloud condensation nuclei (CCN) and wanted to ask for a clarification. I am not sure if this is the correct forum, but the dimensions play a role here. So the number_concentration_of_cloud_condensation_nuclei_in_air is 3D variable and when used with an additional scalar coordinate the variable would be 5D (3D+scalar+time), which seems to be a problem for CDO. Documentation for CDO states it only supports variables upto 4 dimensions, which would make the CCN variables unusable. How the extra dimension should be tackled?

[taylor13]

Section 5.7 of the conventions states:

When a variable has an associated coordinate which is single-valued, that coordinate may be represented as a scalar variable (i.e. a data variable which has no netCDF dimensions). Since there is no associated dimension these scalar coordinate variables should be attached to a data variable via the coordinates attribute.

So the array for storing the variable can be 4D and the scalar dimension recorded using the cooridinates attribuite attached to the variable.

[tommibergman]

Ah that was my misunderstanding then. Different CCNs will just have different scalar dimension and separate physical parameters.

[japamment]

Hi Fiona @fmoconnor

I see that some of your proposals have received quite a lot of discussion, while others have not been commented on. The following summarises the current status of all the names in this issue. For ease of reference I have numbered them 1-11 according to the order they were first proposed.

Many of the names are close to acceptance, although a few need further attention. In particular, please could you take a look at my comments on 4, 7, 8, 9 and 10.

Any names that are fully agreed and accepted by 4th November will be included in the next update of the standard name table, which is planned for 11th-12th November.

1. atmosphere_absorption_optical_thickness_due_to_nitrate_ambient_aerosol_particles Units: 1 Description: The optical thickness is the integral along the path of radiation of a volume scattering/absorption/attenuation coefficient. The radiative flux is reduced by a factor exp(-optical_thickness) on traversing the path. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the optical thickness applies at specific wavelengths or frequencies. "Absorption optical thickness" means that part of the atmosphere optical thickness that is caused by the absorption of incident radiation. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. "Ambient_aerosol" means that the aerosol is measured or modelled at the ambient state of pressure, temperature and relative humidity that exists in its immediate environment. "Ambient aerosol particles" are aerosol particles that have taken up ambient water through hygroscopic growth. The extent of hygroscopic growth depends on the relative humidity and the composition of the particles. To specify the relative humidity and temperature at which the quantity described by the standard name applies, provide scalar coordinate variables with standard names of "relative_humidity" and "air_temperature". 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 chemical formula for the nitrate anion is NO3-.

The name and units look fine. With the addition of one sentence about nitrate at the end of the description, I think this name is ready to be accepted. If no further comments are received in the next seven days, this name will be accepted for publication in the standard name table.

2. tendency_of_atmosphere_mole_concentration_of_hydroxyl_radical_due_to_chemical_production_from_atomic_singlet_oxygen_and_water_vapor Units: mol m-3 s-1 Description: "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". The phrase "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical production" means the result of all chemical reactions within the medium (here, atmosphere) that produce a certain amount of the particular species. In chemistry, a "radical" is a highly reactive, and therefore short lived, species. The chemical formula for the hydroxyl radical is OH. The chemical formula for atomic_singlet_oxygen is O1D. The chemical formula for water vapor is H2O. Here, the production of hydroxyl radical is equal to 2k[O1D][H2O], i.e., 2 hydroxyl radicals are formed from the reaction of O1D with H2O. For models that do not have O1D as a species, the production of hydroxyl radical may be represented differently but the chemical production should take account of the hydroxyl yield.

This name has been discussed in detail and consensus has been reached (thank you @JonathanGregory @martinjuckes @efisher008). If no further comments are received in the next seven days, this name will be accepted for publication in the standard name table.

For consistency, I will also make the existing name 'photolysis_rate_of_ozone_to_1D_oxygen_atom' into an alias for photolysis_rate_of_ozone_to_atomic_singlet_oxygen as suggested by @JonathanGregory. This in turn necessitates updating the description of the existing name photolysis_rate_of_ozone. These changes will also be accepted for publication if no further comments are received in the next seven days.

3. surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes Units: kg m-2 s-1 Description: The surface called "surface" means the lower boundary of the atmosphere. "Upward" indicates a vector component which is positive when directed upward (negative downward). In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. The chemical formula for methane is CH4. The mass is the total mass of the molecules. The specification of a physical process by the phrase "dueto" 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. "Emission" means emission from a primary source located anywhere within the atmosphere, including at the lower boundary (i.e. the surface of the earth). "Emission" is a process entirely distinct from "re-emission" which is used in some standard names.

The name, units and description are all fine. If no further comments are received in the next seven days, this name will be accepted for publication in the standard name table.

4. tendency_of_atmosphere_moles_of_methane_due_to_chemical_destruction_by_hydroxyl Units: mol m-3 s-1 Description: "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". The phrase "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical destruction" means the result of all chemical reactions within the medium (here, atmosphere) that destroy a certain amount of a particular species from the medium. The chemical formula for methane is CH4. The chemical formula for hydroxyl is OH.

A quantity described as a tendency_of_atmosphere_moles should have units of mol s-1. However, the units and description in the proposal make me think that the name should be tendency_of_atmosphere_mole_concentration_of_methane_due_to_chemical_destruction_by_hydroxyl. Please can you confirm if this is correct @fmoconnor? Also, could we change the name to say hydroxyl_radical for consistency with existing names and your other proposals? If these changes can be agreed then this name would be ready to accept.

5. surface_downward_mass_flux_of_methane_due_to_soil_biological_consumption Units: kg m-2 s-1 Description: 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 chemical formula for methane is CH4. The mass is the total mass of the molecules. The specification of a physical process by the phrase "dueto" 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 name, units and description are all fine. If no further comments are received in the next seven days, this name will be accepted for publication in the standard name table.

6. tendency_of_atmosphere_mole_concentration_of_ozone_due_to_net_chemical_production Units: mol m-3 s-1 Description: "Mole concentration" means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". The phrase "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Net chemical production" means the net result (calculated as production minus destruction) of all chemical reactions within the medium (here, atmosphere) that produce or destroy a particular species. The chemical formula for ozone is O3. The IUPAC name for ozone is trioxygen.

The name and units look fine. I have suggested some modifications to the description text for consistency with existing net_chemical_production standard names, but I don't think these change the meaning in any way. If no further comments are received in the next seven days, this name will be accepted for publication in the standard name table.

7. tendency_of_atmosphere_moles_of_molecular_hydrogen_due_to_chemical_production Units: mol m-3 s-1 Description: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical Production" refers to all chemical reactions within the medium (here, atmosphere) that produce a certain amount of a particular species from the medium. The chemical formula for molecular hydrogen is H2.

A quantity described as a tendency_of_atmosphere_moles should have units of mol s-1. However, the units and description in the proposal make me think that the name should be tendency_of_atmosphere_mole_concentration_of_molecular_hydrogen_due_to_chemical_production. Please can you confirm if this is correct @fmoconnor? If so, we can change the name and this one would be ready to accept.

8. tendency_of_atmosphere_moles_of_molecular_hydrogen_due_to_chemical_destruction Units: mol m-3 s-1 Description: Mole concentration means number of moles per unit volume, also called "molarity", and is used in the construction "mole_concentration_of_X_in_Y", where X is a material constituent of Y. A chemical or biological species denoted by X may be described by a single term such as "nitrogen" or a phrase such as "nox_expressed_as_nitrogen". "tendency_of_X" means derivative of X with respect to time. The specification of a physical process by the phrase "dueto" 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. "Chemical Destruction" refers to all chemical reactions within the medium (here, atmosphere) that destroys a certain amount of a particular species from the medium.

As with proposal 7, a quantity described as a tendency_of_atmosphere_moles should have units of mol s-1. The units and description suggest the name should be tendency_of_atmosphere_mole_concentration_of_molecular_hydrogen_due_to_chemical_destruction. If this is correct, we can change the name and this one would be ready to accept.

9. number_concentration_of_cloud_condensation_nuclei_at_0.2_percent_supersaturation_in_air Units: m-3 Description: "Number concentration" means the number of particles or other specified objects per unit volume. The cloud condensation nuclei number concentration is the total number of aerosol particles per unit volume independent of and integrated over particle size that act as condensation nuclei for liquid-phase clouds. A coordinate variable with the standard name of relative_humidity should be specified to indicate that the property refers to a specific supersaturation of 0.2 percent with respect to liquid water. The ability of a particle to act as a condensation nucleus is determined by its size, chemical composition, and morphology.

There remains a question as to whether the existing name number_concentration_of_cloud_condensation_nuclei_in_air could be used for this quantity along with a coordinate variable with standard name of relative_humidity. The question posed by @martinjuckes is whether 0.2 percent supersaturation is the same as 100.2 percent relative humidity. This name remains under discussion.

10. number_concentration_of_cloud_condensation_nuclei_at_1_percent_supersaturation_in_air Units: m-3 Description: "Number concentration" means the number of particles or other specified objects per unit volume. The cloud condensation nuclei number concentration is the total number of aerosol particles per unit volume independent of and integrated over particle size that act as condensation nuclei for liquid-phase clouds. A coordinate variable with the standard name of relative_humidity should be specified to indicate that the property refers to a specific supersaturation of 1 percent with respect to liquid water. The ability of a particle to act as a condensation nucleus is determined by its size, chemical composition, and morphology.

There remains a question as to whether the existing name number_concentration_of_cloud_condensation_nuclei_in_air could be used for this quantity along with a coordinate variable with standard name of relative_humidity. The question posed by @martinjuckes is whether 1 percent supersaturation is the same as 101 percent relative humidity. This name remains under discussion.

Whatever the conclusion on the equivalence (or not) of supersaturation and relative humidity, proposals 9 and 10 should be combined into a single standard name and associated with an appropriate coordinate variable rather than containing numerical values.

11. tendency_of_atmosphere_mass_content_of_ammonium_dry_aerosol_particles_due_to_net_chemical_production Units: kg m-2 s-1 Description: "Content" indicates a quantity per unit area. The "atmosphere content" of a quantity refers to the vertical integral from the surface to the top of the atmosphere. For the content between specified levels in the atmosphere, standard names including "content_of_atmosphere_layer" are used. The mass is the total mass of the particles. The phrase "tendency_of_X" means derivative of X with respect to time. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air itself. Aerosol particles take up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the particles. "Dry aerosol particles" means aerosol particles without any water uptake. The specification of a physical process by the phrase "dueto" 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. "Net chemical production" means the net result (calculated as production minus destruction) of all chemical reactions within the medium (here, atmosphere) that produce or destroy a particular species. The chemical formula for the ammonium cation is NH4+.

The name and units look fine. I have suggested some minor amendments to the description text for consistency with existing net_chemical_production standard names. If no further comments are received in the next seven days, this name will be accepted for publication in the standard name table.

Best wishes, Alison

[taylor13]

regarding 3: surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes

There exist the following similar quantities (all with canonical units of kg m-2 s-1): surface_downward_mass_flux_of_methane_due_to_non_wetland_soil_biological_consumption surface_downward_mass_flux_of_methane_due_to_wetland_biological_consumption surface_net_upward_mass_flux_of_methane_due_to_emission_from_wetland_biological_processes surface_upward_mass_flux_of_methane_due_to_emission_from_fires surface_upward_mass_flux_of_methane_due_to_emission_from_herbivorous_mammals surface_upward_mass_flux_of_methane_due_to_emission_from_termites surface_upward_mass_flux_of_methane_due_to_emission_from_wetland_biological_production

And there are additional surface mass fluxes of methane but described with different words (again in canonical units of kg m-2 s-1) : tendency_of_atmosphere_mass_content_of_methane_due_to_emission tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_agricultural_production tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_agricultural_waste_burning tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_energy_production_and_distribution tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_forest_fires tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_industrial_processes_and_combustion tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_land_transport tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_maritime_transport tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_residential_and_commercial_combustion tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_savanna_and_grassland_fires tendency_of_atmosphere_mass_content_of_methane_due_to_emission_from_waste_treatment_and_disposal

All but the first of these tendencies could probably be equivalently described as "surface_upward_mass_fluxes", so my question is why do we describe some methane emissions as surface fluxes and others as tendencies of atmosphere mass content?

For the new name proposed surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes, couldn't the name surface_net_upward_mass_flux_of_methane_due_to_emission be used but with cell_measures = "area: mean where fresh_free_water" ? [Or if you want to omit methane emissions from rivers, we could define a new area_type as "fresh_water_lakes"]

[taylor13]

Regarding standard names 9 & 10, for other similarly-constructed names, the term "threshold" has been used, but that doesn't seem right here. We could say number_concentration_of_cloud_condensation_nuclei_assuming_a_specified_relative_humidity (I think "in air is obvious from the context: "cloud and relative humidity"). Then the scalar coordinate would have the standard_name relative_humidity.

[JonathanGregory]

I agree with Alison's comment

Whatever the conclusion on the equivalence (or not) of supersaturation and relative humidity, proposals 9 and 10 should be combined into a single standard name and associated with an appropriate coordinate variable rather than containing numerical values.

Along the lines of what Karl said, I'd suggest number_concentration_of_cloud_condensation_nuclei_assuming_reference_relative_humidity.

[taylor13]

Jonathan's variant is better because, as I now seem to recall, it is more consistent with other names (i.e.., replace "specified" with "reference")

[japamment]

@taylor13 @JonathanGregory

Thank you for your helpful comments.

Some of the names can now be accepted. This is an updated summary of all the proposals.

The following names have not received any further comments in the last seven days and are now accepted for publication in the standard name table: (1) atmosphere_absorption_optical_thickness_due_to_nitrate_ambient_aerosol_particles Units: 1 (2) tendency_of_atmosphere_mole_concentration_of_hydroxyl_radical_due_to_chemical_production_from_atomic_singlet_oxygen_and_water_vapor Units: mol m-3 s-1 (5) surface_downward_mass_flux_of_methane_due_to_soil_biological_consumption Units: kg m-2 s-1 (6) tendency_of_atmosphere_mole_concentration_of_ozone_due_to_net_chemical_production Units: mol m-3 s-1 (11) tendency_of_atmosphere_mass_content_of_ammonium_dry_aerosol_particles_due_to_net_chemical_production Units: kg m-2 s-1 The names will be added in the update planned for 11th/12th November.

The following names are still under discussion. (4), (7), (8) @fmoconnor please can you confirm whether these names should be changed to use mole_concentration to agree with the proposed units and descriptions? This would be in place of tendency_of_atmosphere_moles.

(9) and (10) @fmoconnor would you be okay to follow Jonathan and Karl's suggestion of number_concentration_of_cloud_condensation_nuclei_assuming_reference_relative_humidity with a scalar coordinate variable of relative_humidity to specify the reference value? I think this is a good approach.

(3) surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes Units: kg m-2 s-1 @taylor13 I think that the two syntaxes have developed over time, depending on whether the scientists proposing the names were more interested in the land/sea surface processes that cause emissions, or attributing sources of atmospheric concentrations after the gases have been emitted.

It is perhaps worth noting that, were we to try rationalising all the surface_Xward_mass_flux and tendency_of_atmosphere_mass_content names in the standard name table (not only for methane), it would be a large exercise requiring a lot of care and even then there may be some names we couldn't completely rationalise. It is something we could consider as a separate issue, as it is beyond the scope of the current CMIP7 proposals.

I agree that for the current proposal we could do as you suggest:

For the new name proposed surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes, couldn't the name surface_net_upward_mass_flux_of_methane_due_to_emission be used but with cell_measures = "area: mean where fresh_free_water" ? [Or if you want to omit methane emissions from rivers, we could define a new area_type as "fresh_water_lakes"]

This would be equivalent to the proposed name. Personally, I don't have a strong view on which approach to take and would be happy to go with the majority view.

Best wishes, Alison

[JonathanGregory]

Dear Karl and Alison

I suppose that the surface flux of a species into the atmosphere due to process X is not necessarily equal to the tendency of the atmosphere mass content of the species due to process X because the species is transported within the atmosphere. The two quantities would have the same global integral without being equal locally if the species is conserved. For example, consider the extreme case where the atmosphere constantly and instantaneously mixes methane so that its concentration is the same everywhere all the time. For a surface flux of any given size, wherever it occurs, the atmosphere content will have the same geographically uniform tendency. In addition, if the species is not conserved, because it's chemically reactive or removed by some physical process, a change in surface flux would not necessarily equal the change in tendency of content, even in the global integral. For example (only a vague example, since I don't know the details!), when biological production of oxygen first began, the tendency of the oxygen content of the atmosphere didn't go up much, because other substances exposed to the atmosphere were being oxidised (especially iron). Once that had finished, the oxygen content rose much more rapidly, even though the fluxes might not have changed. Best wishes

Jonathan

[taylor13]

Hi Jonathan, I get your point. I was thinking in terms of an instantaneous tendency due to surface emissions, which for a conservative species must equal the local surface flux, but when averaged, say, over a year could be different.

I think that when a species is not conserved, when we say "tendency due to surface emission", we should reserve this to the direct emission of the species into the atmosphere an not some precursor. So, we would not accept a standard name such as atmospheric tendency of CO2 due to methane emission or tendency of ozone due to surface N2O emissions, even thought fluxes of the precursors obviously impact the tendency of any eventual chemical product. Wouldn't this be true even if the chemical reaction was a quick one that removed a chemical almost immediately after entering the atmosphere?

[martinjuckes]

Hi Fiona @fmoconnor, I'm still a little unclear about what the phrase "the property refers to a specific supersaturation of 1 percent with respect to liquid water" means. Is it (a) about those particle which would act as cloud condensation nuclei if the ambient supersatutarion were to be 1% or is it (b) the concentration of cloud condensation nuclei in those parts of the cloud which have an ambient supersaturation of 1%?

[fmoconnor]

Thank you @martinjuckes @JonathanGregory @taylor13 @tommibergman @japamment for your comments on these proposals and for the detailed and constructive discussions about some of them! Apologies too for the radio silence on my part - I have another deadline to deal with!

Prompted by @japamment, here are my remaining comments.

For 4: tendency_of_atmosphere_moles_of_methane_due_to_chemical_destruction_by_hydroxyl, from reading the discussion, I am happy with the proposed change to the originally proposed name to tendency_of_atmosphere_mole_concentration_of_methane_due_to_chemical_destruction_by_hydroxyl_radical

For 7: I am happy to change the proposed name from tendency_of_atmosphere_moles_of_molecular_hydrogen_due_to_chemical_production to tendency_of_atmosphere_mole_concentration_of_molecular_hydrogen_due_to_chemical_production

For 8: As above, I am happy to change tendency_of_atmosphere_moles_of_molecular_hydrogen_due_to_chemical_destruction to tendency_of_atmosphere_mole_concentration_of_molecular_hydrogen_due_to_chemical_destruction

[fmoconnor]

For 9 and 10: Firstly, to answer the question from @martinjuckes, I confirm that 1 percent supersaturation is the same as 101 percent relative humidity. As far as I understand, it represents the concentration of particles which would be large enough to act as cloud condensation nuclei if the ambient supersatutarion was 1%.

Secondly, I am also happy to remove the numeric values from the proposed names (which, as suggested, can be specified as a scalar co-ordinate). It means that the corresponding variables will have different physical parameters in CMIP7 (these have been proposed already) but share the same CF name. That will work well.

Finally, I haven't been able to get as much feedback from the AerChemMIP community as I would like on the actual names themselves. So, in the interest of timescales, I'm happy with the suggested name number_concentration_of_cloud_condensation_nuclei_assuming_reference_relative_humidity. For completeness, I think the metadata for both 9 and 10 already seems to cover the scalar co-ordinate and is suitable as is.

[fmoconnor]

I see that there has been a lot of discussion about 3: surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes.

Following the discussion between @taylor13 and @JonathanGregory, I want to make clear that this name refers to the direct emission of the species (methane in this case) into the atmosphere. I added the term net, because like wetlands, there is both production and consumption of methane within lakes but from an atmosphere perspective, we want the net emission into the atmosphere.

I think I would prefer to stick with the name surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes rather than use surface_net_upward_mass_flux_of_methane_due_to_emission with cell_measures = "area: mean where fresh_free_water". As is, the new name would be consistent with the equivalent emission flux from wetlands (i.e., surface_net_upward_mass_flux_of_methane_due_to_emission_from_wetland_biological_processes). Would that be acceptable?

[JonathanGregory]

Dear Fiona @fmoconnor

Thanks for considering all these discussions, and for your flexibility. Yes, I agree with your reasoning for preferring surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes. You regard "emission from freshwater lakes" as a process, rather than "emission" as a process which happens to occur in freshwater lakes. That makes sense.

Best wishes

Jonathan

[taylor13]

I'm also comfortable enough sticking with surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes

[fmoconnor]

[like] Fiona O'Connor reacted to your message:

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I'm also comfortable enough sticking with surface_net_upward_mass_flux_of_methane_due_to_emission_from_freshwater_lakes

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