Table 1-02: Measurement unit - new unit for GHG observation

[SakiOhkubo]

Initial request

To add some new units for GHG and other related gas observation listed in WDCGG.

Amendment details

Add the following units:

• pmol/kg
• nmol/kg
• fmol/kg
• per meg

Notation	Name	Description
pmol.kg-1	picomole per kilogram	SI derived unit of amount per unit mass; SI base unit equivalent: 1E-12 mol.kg-1
nmol.kg-1	nanomole per kilogram	SI derived unit of amount per unit mass; SI base unit equivalent: 1E-9 mol.kg-1
fmol.kg-1	femtomole per kilogram	SI derived unit of amount per unit mass; SI base unit equivalent: 1E-15 mol.kg-1
permeg	per meg	Dimensionless number, expressed as a fraction of 1000000; SI base unit equivalent: 0.000001; also referred as parts per million (ppm)

Comments

These units are used as metadata for some observation in WDCGG.
https://gaw.kishou.go.jp/documents/db_list/unit

Requestor(s)

WDCGG

Stakeholder(s)

Enter list of stakeholder(s).

Publication(s)

Manual on Codes (WMO-No. 306), Volume I.3, WMO Codes Registry, Code table 1-02, Measurement unit,http://codes.wmo.int/wmdr/unit

Expected impact of change

None

Collaborators

No response

References

No response

Validation

No response

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.02.03-TT-WIGOSMD notes:
team agrees to work on for FT2023-2; @gaochen-larc will take the lead;

[gaochen-larc]

I endorse the proposed additions of the trace gas units. I would also like to recommend adding three other units widely used in WDCGG and the literature: "ppm", "ppb", and "ppt".

[gaochen-larc]

ppt, parts per trillion, Dimensionless number, expressed as a fraction of 1E12; SI base unit equivalent: 1E-12
ppb, parts per billion, Dimensionless number, expressed as a fraction of 1E9; SI base unit equivalent: 1E-9
ppm, parts per million, Dimensionless number, expressed as a fraction of 1000000; SI base unit equivalent: 0.000001

ppm is the same as per meg, but used in different research fields. "ppm" is commonly used to represent the abundance of CO2 while "per meg" is used to denote the changes in O2/N2 ratio.

[SakiOhkubo]

Thank you for your comment.
Currently, we use "umol.mol-1", "nmol.mol-1" and "pmol.mol-1" instead of "ppm", "ppb", and "ppt" when we need to use the WMDS codes.
However, if possible, we would like to add "ppm", "ppb", and "ppt" besides "umol.mol-1", "nmol.mol-1" and "pmol.mol-1", as you suggested.

[markusfiebig]

I would recommend to go for the SI recommended units, which would be "umol.mol-1", "nmol.mol-1" and "pmol.mol-1". With these units, it is clear that we mean amount fraction, i.e. number fraction, not mass fraction, which can be a confusion with ppt, ppb, and ppm. As compromise, we could allow the pp units as synonym of the preferred SI units.

As a general rule, we should avoid "tribal language", which the pp units are.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.02.16-TT-WIGOSMD notes:

Gao can create another issue for "pp*" stuff and we can accept the original proposal.

[gaochen-larc]

I agree with @amilan17. Let's go forward with the current proposal and I will create a new issue later.

[joergklausen]

I support Markus in not supporting pp* notation. It is less clear. @gaochen-larc : please add the pp* notations to the Descriptions in the issue above, along the lines of "Note: Sometimes refered to as pp*".

[gaochen-larc]

@markusfiebig @joergklausen: I made a change in the description of "permeg". Could you please take a look? I recognize "ppm", "ppb", and "ppt" are vague. At the same time, they are widely used in literature and current data reporting practice, e.g. NOAA GML (previously CMDL) and data archived in the WDCGG. We may need a compromise solution to mitigate the impact of the entrenched "tribal" practice.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023-03-17-TT-WIGOSMD notes:
ready for branch

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.04.21-TT-WIGOSMD notes:
Gao will update the branch

[gaochen-larc]

branch updated.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.05.04-TT-WIGOSMD notes:
@meulenvd will review; @gaochen-larc will put new codes in alphabetical order;

[gaochen-larc]

new codes sorted in alphabetical order

[joergklausen]

Branch reviewed, deletions seem to cancel additions, not sure ...

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.06.01-TT-WIGOSMD notes:
in validation

[meulenvd]

Reviewed, no comments

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.06.15-TT-WIGOSMD notes:

@gaochen-larc create PR;

[gaochen-larc]

Hope I did it correctly

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/2023.06.30-TT-WIGOSMD notes:

valid;