wmo-im
1-01-01 Remove duplicate temperature variable and improve name and description
Introduction
This issue is related to another issue from FT-2021-2: 1-01-01 Remove spatial extent from variable name. According to this amendment, a variable such as "Atmospheric pressure profile" was deprecated and replaced by a combination of the variable "Atmospheric pressure" and the observed geometry "vertical profile".
The implementation of this change in OSCAR/Surface and the neccessary migrations (mainly for the WDQMS related variables) is currently in planning. The following entries of the variable table pose a problem for this effort:
| notation | name | description | remark |
|---|---|---|---|
| 224 | Air temperature (at specified distance from reference surface) | currently in use by OSCAR and WDQMS | |
| 12166 | Temperature | not yet included in OSCAR and WDQMS |
The deprecated variable "Temperature profile" (https://codes.wmo.int/wmdr/ObservedVariableAtmosphere/_227) was superseded by 12166, Temperature. 224, Air temperature (at specified distance from reference surface), which is used in OSCAR and WDQMS to describe a point observation and can be expressed as a combination of the new variable "Temperature" + geometry "point", remained in the table - possibly by mistake.
To proceed with the migration in the dependent tools, a clean-up is needed.
Amendment details
update 28 Aug 2025
| notation | name | description | remark |
|---|---|---|---|
| 224 | Air temperature (at specified distance from reference surface) | retire code and replace by 12166 in OSCAR | |
| 12166 | Air temperature | The temperature indicated by a thermometer exposed to the air in a place sheltered from direct solar radiation. |
- Retire 224
- Rename 12166 to "Air temperature", so that it is consistent with other temperature variables, such as "Soil temperature" etc., and add a description.
Requestor(s)
@kurt-hectic, @nuneslf, @fstuerzl
TT-WOT
Stakeholder(s)
No response
Applications or Systems
- [x] OSCAR/Surface
- [ ] OSCAR/requirements
- [x] GAWSIS
- [ ] Radar/DB
- [ ] OceanOPS
- [ ] WHOS
- [x] WDQMS
- [ ] GBON Compliance Monitor
- [ ] Other
Expected impact of change
HIGH
Consultations
No response
Data exchange
No response
Comments
No response
https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2025.03.20 notes:
- Franziska presented, noting that the system can now support geometry
- The team discussed the pros/cons of the proposal
- next consult with WDQMS / ET-EOSDE on the requirements for air temperature @reginayasmin
- Presentation on air temperature: https://www.bipm.org/documents/20126/70327967/WSApr2022-02-Merlone-Issues+with+the+measurand-v2.pdf/b7f79e0e-2325-2c56-d6bd-de0daeb44836
similar variables/parameters
- OSCAR/Requirements:
- https://space.oscar.wmo.int/variables/view/air_temperature_near_surface
- https://space.oscar.wmo.int/variables/view/atmospheric_temperature
- BUFR code Air temperature at 2 m
- Common Code: http://codes.wmo.int/common/quantity-kind/airTemperature
I support the proposal to "Supersede 224 by 12166" and to "Rename 12166 to "Air temperature"" and add a description to this one - this is critical, all entries in code lists should have one. I'd also suggest reviewing the names and descriptions of variables 224 and 226 for consistency, for example, to be renamed as follows: 225 = Dew-point temperature 226 = Extreme temperature (min, max)
TT-WIGOSMD notes
- Franziska updated the issue summary based on the conversations with WIGOS Operational Tools; @fstuerzl create new issue to separate temperature and humidity proposals. Create/update the branches and tag Gao and Joerg to review; Washington supports because hydro also was water temperature;
@nuneslf @reginayasmin @fstuerzl @joergklausen Does this need more planning and discussion? Should we delay this change until the next FT in 2026?
TT-WIGOSMD notes
- Franziska updated the issue summary based on the conversations with WIGOS Operational Tools; @fstuerzl create new issue to separate temperature and humidity proposals. Create/update the branches and tag Gao and Joerg to review; Washington supports because hydro also was water temperature;
Humidity proposal is created under https://github.com/wmo-im/wmds/issues/594
Agree with the approach and here is an attempt for a draft description.
Description: temperature of air (at a location and time) from measurement not influenced by direct solar radiation and air motion
@nuneslf @reginayasmin @fstuerzl @joergklausen Does this need more planning and discussion? Should we delay this change until the next FT in 2026?
This shouldn't be delayed to 2026.
Agree with the approach and here is an attempt for a draft description. Description: temperature of air (at a location and time) from measurement not influenced by direct solar radiation and air motion
Alternative, more generic suggestion for the description:
- temperature of air measured by using an instrument.
I'd also suggest reviewing the names and descriptions of variables 224 and 226 for consistency, for example, to be renamed as follows: 225 = Dew-point temperature 226 = Extreme temperature (min, max)
@nuneslf a new issue should be opened to address this request.
@joergklausen @fstuerzl Recently the team decided to avoid superseding one value by another because it adds a level of complexity/confusion. Is it ok to just change the status to "Retired" instead?
@joergklausen @fstuerzl Recently the team decided to avoid superseding one value by another because it adds a level of complexity/confusion. Is it ok to just change the status to "Retired" instead?
I think "Retired" is better.
https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2025.06.12 notes:
- Franziska is ok with "Retired" as long OSCAR/Surface knows the ideal replacement code. @fstuerzl update branch with new definition below.
Definition: Measured temperature of air. It is the best practice to minimize the impact of direct radiation on the measurement and/or correct the influence of air motion.
moved back to in progress because the definition is still under discussion.
The WMO defines air temperature as the temperature of the air surrounding a location, typically measured at a height of 2 meters above the ground or ocean surface. It is a crucial measurement for understanding weather and climate and is often used in daily weather reports.
Dear Anna,
The WMO defines air temperature as the temperature of the air surrounding a location, typically measured at a height of 2 meters above the ground or ocean surface. It is a crucial measurement for understanding weather and climate and is often used in daily weather reports.
Kind regards,
Anne Kamau. O/S Focal Point -Kenya.
On Thu, Jul 10, 2025 at 3:31 PM Anna Milan @.***> wrote:
amilan17 left a comment (wmo-im/wmds#583) https://github.com/wmo-im/wmds/issues/583#issuecomment-3057258099
What is the definition of air temperature?
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to do:
- pick a suggested definition and use this, it can be revised as needed in further fast-track proposals.
- review and approve PR
@kamauanne-cpu Thank you for this definition. Where did you find this definition? Can you provide a reference or URL?
The WMO defines air temperature as the temperature of the air surrounding a location, typically measured at a height of 2 meters above the ground or ocean surface. It is a crucial measurement for understanding weather and climate and is often used in daily weather reports.
Dear Anna, Sorry for the definition I gave and I wish to withdraw. The definition according to Environmental Monitor- https://www.fondriest.com/news/air temperature.htm reads: Air temperature is the thermal state of the atmosphere that is determined by the average kinetic energy of air molecules; as they move faster the temperature increases, reflecting greater thermal energy in the air. I regret the mistake in the first definition that I gave.
Kind regards,
Anne Kamau.
On Tue, Jul 15, 2025 at 8:26 PM Anna Milan @.***> wrote:
amilan17 left a comment (wmo-im/wmds#583) https://github.com/wmo-im/wmds/issues/583#issuecomment-3074544343
@kamauanne-cpu https://github.com/kamauanne-cpu Thank you for this definition. Where did you find this definition? Can you provide a reference or URL?
The WMO defines air temperature as the temperature of the air surrounding a location, typically measured at a height of 2 meters above the ground or ocean surface. It is a crucial measurement for understanding weather and climate and is often used in daily weather reports.
— Reply to this email directly, view it on GitHub https://github.com/wmo-im/wmds/issues/583#issuecomment-3074544343, or unsubscribe https://github.com/notifications/unsubscribe-auth/BK3CDEV3HH2BSMR2PUOQI6D3IU2WHAVCNFSM6AAAAABZLHQO4CVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTANZUGU2DIMZUGM . You are receiving this because you were mentioned.Message ID: @.***>
What is the definition of air temperature?
@amilan17 @kamauanne-cpu
Sorry for this intrusion in that discussion Anna. I think the definition by @gaochen-larc is almost identical to the definition found in the International Meteorological Vocabulary (1992). Air temperature : The temperature indicated by a thermometer exposed to the air in a place sheltered from direct solar radiation. https://library.wmo.int/doc_num.php?explnum_id=4712
A more detailed definition, which includes the above, is found in: Guide to instruments and methods of observation (WMO-No. 8), Volume I, Section 2.1.1 https://library.wmo.int/idurl/4/68695
Hope that helps. Best regards Charles
Thank you @scoubidoudou for the clarification and the definition from the links you have given.
Kind regards,
Anne.
I like the WMO's definition provided by @scoubidoudou. Thanks! Should we consider to add a sentence about measurement of air temperature from a flying aircraft? or we can introduce another variable at later time...
The temperature indicated by a thermometer exposed to the air in a place sheltered from direct solar radiation . The static air temperature or outside temperature refers to measurement of air temperature from an aircraft after correcting for air motion.
Update definition to "The temperature indicated by a thermometer exposed to the air in a place sheltered from direct solar radiation." This is consistent with the IMV definition and http://codes.wmo.int/common/quantity-kind/airTemperature.
Add as amendment to FT2025-2 proposal because this needs to be addressed by WDQMS before FT2026-2.
Feeback during NFP review:
Following further investigation, I would like to suggest one change.
Concerning this record: Air temperature sensors are not universally shielded from direct solar radiation, such as the case with sensors used in upper air sondes.
Therefore a description of the following is suggested:
The temperature indicated by a thermometer exposed to the air (shielded or unshielded) in a manner in accordance to the method of observation.
Kind regards
Karl Monnik
Manager: Data Requirements & Quality Data Program, Data & Digital Group
[12166] (Air temperature) The definition for Air temperature is given for a long time in the IMV (WMO-No. 188) and in the obsolete Manual to the GOS (WMO-No. 544): [A1390] air temperature: The temperature indicated by a thermometer exposed to the air in a place sheltered from direct solar radiation. However it was decided to remove this definition during the transfer of text from the Manual to the GOS into the Manual to the WIGOS (WMO-No. 1160). The point is that this definition is trivial and not a definition for temperature. In fact it defines the function of a thermometer not the quantity. In principal, a variable or quantity cannot be expressed by a device measuring that quantity, We are dealing here with the base SI quantity temperature, but restricted to the gaseous phase (so temperature of a gas, or air temperature). The (thermodynamic) temperature itself is defined as the partial derivative of internal energy with respect to entropy at constant volume and constant number of particles in the system:
T = (∂U /∂S )V,N
where U is internal energy , S is entropy, V is volume, and N is number of particles. Note: For the purpose of practical measurements, the International Temperature Scale of 1990, ITS-90, is a close approximation to the thermodynamic temperature scale. Thermometers, calibrated traceable to the SI standard, report the ITS-90 temperature. If a new scale is adopted (to be expected soon), thermometers will have to be adjusted to the new scale. So we may define an air temperature for meteorological practices as a temperature that is based on the present International Temperature Scale.
More NFP suggestions: Dear Anna, I agree with Karl that the proposed temperature definition does not apply to upper air sondes temperature sensors. However, I think there is a need to retain "shielded from direct solar radiation" in the definition as this is a very important point to ensure that the air temperature readings are not biased.
I would suggest the following description:
The temperature indicated by a thermometer exposed to the air (for surface measurements, in a place sheltered from direct solar radiation).
Regards, Olivia Shuk-ming Lee
NFP-OSCAR/Surface of Hong Kong, China
However, "The temperature indicated by a thermometer exposed to the air" is not a definition of air temperature. It defines the function of a thermometer, not the quantity temperature. More over other techniques exist that enable measuring temperature of a gas with a higher accuracy, traceable to SI and according to ITS90. Also a thermometer measures the temperature of a sensor (eg Pt element) assuming that its value equals the air around it.