add water vapour mixing ratio to atmospheric variables (1-01-01)

[amilan17]

Initial request

OSCAR/Requirements updated Water Vapour mixing ratio in summer of 2024. This issue is an attempt to align with WIGOS metadata codes.

Add water vapour mixing ratio to atmospheric variables (1-01-01)

Amendment details

Name	Description
Water Vapour Mixing Ratio	"3D field of water vapour mixing ratios in the UTLS. Mixing ratio is the mole fraction of a substance in dry air (UTLS, MUS)"

Requestor(s)

GOCS, OSCAR Requirements, @kpremec

Stakeholder(s)

Enter list of stakeholder(s).

Applications or Systems

• OSCAR/Surface
• OSCAR/requirements
• Radar/DB
• OceanOPS
• WHOS
• WDQMS
• GBON Compliance Monitor
• Other

Expected impact of change

None

Collaborators

No response

References

https://space.oscar.wmo.int/variables/view/water_vapour_mixing_ratio

Comments

This may be related to
Water vapour (no definition) which doesn't have a definition.

Publication(s)

Example: Manual on Codes (WMO-No. 306), Volume I.3, WMO Codes Registry, Code table 1-01-01

Validation

No response

[amilan17]

related codes:

notation	path	domains	tags	name	description
46	252	\Atmosphere\Humidity			Integrated water vapour
49	255	\Atmosphere\Humidity			Water vapour pressure
579	12165	\Atmosphere\Humidity		\Atmosphere\Humidity\Water vapour	Water vapour
661	12249	\Atmosphere\Humidity		atmosphere,humidity	Relative humidity (with respect to water)
662	12250	\Atmosphere\Humidity		atmosphere,humidity	Specific humidity

[amilan17]

@kpremec proposes to remove this part of the definition from O/R and the new WIGOS codes.
"Mixing ratio is the mole fraction of a substance in dry air (UTLS, MUS)"

[kpremec]

Proposal is to extract the 2nd sentence "Mixing ratio is the mole fraction of a substance in dry air (UTLS, MUS)" and add it as a note in OSCAR/Requirements.

[joergklausen]

https://codes.wmo.int/ui/text-search?query=water+vapour produces a long list of entries from grib2, bufr4, and wmdr with clear redundancies.
https://codes.wmo.int/ui/text-search?query=humidity produces an even longer list, again with many redundancies. https://codes.wmo.int/ui/text-search?query=watervapor produces one more hit, of a deprecated variable.
https://codes.wmo.int/ui/text-search?query=mixing+ratio produces another long list, again with many reduncancies.

Cleaning up these codes would require a collaboration between various teams of WMO and presumably, a more fundamental change to grib2 and bufr4 code list management.

For TT-WIGOSMD, the following are relevant in the context of this issue. Definitions were added in italic where none exists.

Notation	Name	Description	Status
252	Integrated water vapour	Total amount of water vapour in a vertical column of air per unit area. Integrated water vapour (IWV) is also known as Precipitable Water Vapour (PWV).	stable
255	Water vapour pressure	Partial pressure of water in the atmosphere	stable
12165	Water vapour	Water in the gaseous phase. [International Vocabulary of Meteorology (WMO-No. 182). 1992.]	stable
251	Humidity (at specified distance from reference surface)		superseded
12249	Relative humidity (with respect to water)	The ratio of the amount fraction of the water vapour in the air to the corresponding amount fraction if the air were saturated with respect to water at a particular pressure and temperature. Relative humidity is typically reported in percent (%). [Based on definition of R1490 in International Vocabulary of Meteorology (WMO-No. 182). 1992.]	stable
12250	Specific humidity	The ratio of the mass of water vapour in the air to the mass of a moist air parcel, where the mass of the moist air parcel is the sum of the mass of water vapour and the dry air. Synonym: Moisture content. [Based on definition of M1750 in International Vocabulary of Meteorology (WMO-No. 182). 1992.]	stable
256	Watervapor profile		superseded
253	Mass mixing ratio	Ratio of the mass of water vapour to the mass of dry air. Based on AMS Glossary od Meteorology.	stable

The term 253 (Mass mixing ratio) is the closest match to the term water vapour mixing ratio used in OSCAR/Requirements. Because 'mass mixing ratio' is conventionally used for 'water vapour mixing ratio', but is ambiguous, it is recommended to rename the current WMDR term and include a mention in the definition, as follows:

Notation	Current Name	New Name	Description	Status
253	Mass mixing ratio	Water vapour mixing ratio	Ratio of the mass of water vapour to the mass of dry air. Often simply called 'mass mixing ratio'. Based on AMS Glossary od Meteorology.

[amilan17]

https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2025.02.20 notes:

@wmo-im/tt-wigosmd to review; Jitze noted that it would be good to simplify this list, and this problem also exists in OSCAR/Requirements

[kamauanne-cpu]

Thanks Anna for this issue.I will look into it. Best regards, Anne.

…

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