wmo-im
Change Sea-ice surface temperature (code 405) to Sea-ice temperature, name, definition, and unit
Initial request
This request is to change the name, definition, and units of the variable Sea-ice surface temperature, code 405, to Sea-ice temperature. While the surface temperature of the sea ice is unquestionably important, it is insufficient for modeling the conductive flux through the ice and hence ice growth. The new definition would include the surface temperature of sea ice, so the current requirement would be satisfied.
Current name: Sea-ice surface temperature Proposed name: Sea-ice temperature Current definition: Temperature of the surface of sea-ice Proposed definition: Sea ice temperature measured at defined vertical levels in the ice and any snow on the ice, including the temperature at the ice and snow surfaces Current units, Measuring and Uncertainy: K, Horizontal: km, Stability: K (per decade) Current units, Measuring and Uncertainy: K, Horizontal: m, Stability: K (per decade)
Amendment details
The existing variable will be updated as follws:
| notation | name | definition |
|---|---|---|
| 405 | Sea-ice temperature | Sea ice temperature measured at defined vertical levels in the ice and any snow on the ice, including the temperature at the ice and snow surfaces |
All the units involved exist and no changes are needed.
Requestor(s)
Enter Group: Global Cryosphere Watch (GCW) POCs:
- Jeff Key ([email protected]), University of Wisconsin
- Stefan Kern, University of Hamburg, [email protected]
- Petra Heil, University of Tasmania and Australian Antarctic Division, [email protected]
- Rodica Nitu, WMO, [email protected]list of requestors.
Stakeholder(s)
Numerical weather prediction for coupled ice-ocean-atmosphere modeling.
Applications or Systems
- [x] OSCAR/Surface
- [x] OSCAR/requirements
- [ ] Radar/DB
- [ ] OceanOPS
- [ ] WHOS
- [ ] WDQMS
- [ ] GBON Compliance Monitor
- [ ] Other
Expected impact of change
LOW
Collaborators
GCW Sea Ice Best Practices team; GCW Cryosphere and Polar Observations (CRYORA) team; Belén Martín Míguez, Ocean Earth System Category (ESAC)
References
Comments
Publication(s)
Manual on Codes (WMO-No. 306), Volume I.3, WMO Codes Registry - WMDR
To be added
Validation
To be added
How the vertical levels are defined is not specified in the above definition. We presume the reference level can be defined and will be part of the metadata accompanying the results of the measurements. If this needs to be part of the definition, then please expand on the proposal.
Hi Joerg. The vertical levels for sea-ice temperature depend on the method applied. Agree these need to be provided in the meta data for each data set.
Will it be possible to provide recommendation in these variable definitions? I have two requests for this:
- Include the vertical level within a "defined depth" to measure the sea-ice temperature. (see next point)
- Change the definition to: "Sea-ice temperature measured at defined vertical levels in the sea ice and any snow on the sea ice. Measurement intervals should be every 0.1m (or less), with the actual temperature measurement (a point measurement) taken at the centre of the vertical measurement interval. Temperatures at the upper sea-ice and snow surfaces need also be measured and included in the data." Best, Petra
To ensure consistency between the metadata for sea ice temperature and the new BUFR template for Cryo station temperature profiles (Issue https://github.com/wmo-im/BUFR4/issues/198) - which includes sea ice temperature where applicable - note that no specific levels were defined in the Cryo station temperature profiles template. Instead, the BUFR code introduces a new element, “0 07 034 Vertical distance of sensor,” to indicate the physical level: positive values are above, and negative values are below the reference level “0 07 030 Height of station ground above mean sea level.”
The proposal received a couple comments. One of them suggests to include a description of the recommended procedure. The code table for the variable names is not the place to describe SOPs, because they can change over time. Also, reference was made to a new BUFR template. Taking this into account, the following is proposed:
| notation | name | definition |
|---|---|---|
| 405 | Sea-ice temperature | Sea ice temperature measured at the centre of defined vertical levels in the ice and any snow on the ice, including the temperature at the ice and snow surfaces. By convention, positive values indicate levels above, and negative values indicate levels below the height of station ground above mean sea level. |
@IARC2000 @rzhangwmo @jeffrkey Please confirm your agreement with the above, so that I can conclude this.
@joergklausen is "at the centre" necessary? does it restrict the definition too much?
notation name definition 405 Sea-ice temperature Sea ice temperature measured at the centre of defined vertical levels in the ice and any snow on the ice, including the temperature at the ice and snow surfaces. By convention, positive values indicate levels above, and negative values indicate levels below the height of station ground above mean sea level.
This is in the ObservedVariableOcean table with the following path used in OSCAR/Surface
Ocean/Cryosphere/Sea ice
@joergklausen, @IARC2000 Regarding "at the centre", I'll defer to Petra. She suggested it so let's go with it. Regarding negative values below the height of the station ground above mean sea level, I'm not so sure. Does this mean that we need to know the height of the station (e.g., an ice mass balance buoy) above mean sea level? All we really want are the temperatures at and below the surface. Furthermore, there will not be any temperature above the surface or station, as that would be the atmosphere. Wouldn't something like this suffice?
Sea ice temperature measured at the centre of defined vertical levels in the ice and any snow on the ice, including the temperature at the ice and snow surfaces. By convention, negative values indicate levels below the station ground.
The (complicated) notion of positive and negative levels originates in @rzhangwmo 's comment. My naïve understanding was to refer the levels to the station elevation. If @jeffrkey 's wording is clear enough for everyone, I am fine with that. I don't feel I should decide here, as personally, I would have referred to the sea ice surface as zero level ... any thoughts?
Updated draft:
| notation | name | definition |
|---|---|---|
| 405 | Sea-ice temperature | Sea ice temperature measured at the centre of defined vertical levels in the ice and any snow on the ice, including the temperature at the ice and snow surfaces. By convention, levels are referenced to the surface of the sea ice, with positive values indicating levels above, and negative values indicating levels below the surface of the sea ice. |
@IARC2000 @rzhangwmo @jeffrkey Is this acceptable as the final draft?
The updated draft is acceptable, in my opinion. I changed the definition in the sections above.
https://github.com/wmo-im/tt-wigosmd/wiki/Meeting.2025.06.12 notes:
@jeffrkey review branch please
Sea ice temperature measured at the centre of defined vertical levels
I don't know why at the centre. For me a level is a plane in space and that is what we refer to in the issue mentioned by @rzhangwmo (https://github.com/wmo-im/BUFR4/issues/198). There we speak about positive and negative heights with reference to a reference level, in the present case “0 07 030 Height of station ground above mean sea level.”, that is, the sea ice surface w/o snow is to be considered as zero level.
Thus I would amend the definition of notation 405 to: Sea ice temperature measured at defined vertical levels in the ice …
@scoubidoudou - Our original definition did not have "at the centre of", if I remember correctly. One of our sea ice experts, Petra Heil, suggested it. I'll have to ask her about it (in a separate email message as I don't know if she sees these comments).
@jeffrkey @Rosie-Bisset branch is updated - do you have a conclusion on the words "at the centre of"?
After consultation with others, we are removing "the centre of" from the definition. Not everybody agrees, but it simplifies the definition and make it more consistent with descriptions of measuring a temperature profiles through snow, permafrost, and sea ice in the literature.
[like] Rodica Nitu reacted to your message: I support Jeff's proposal: The location of the measurement should be described in the best practices and variability in the location would be included in the uncertainty of measurement ("at the centre" would need to be defined, also with its associated uncertainty.)
From: Jeff Key @.> Sent: Tuesday, June 24, 2025 2:04:33 PM To: wmo-im/wmds @.> Cc: Subscribed @.***> Subject: Re: [wmo-im/wmds] Table 1-01-03 change Sea-ice surface temperature (code 405) to Sea-ice temperature, name, definition, and unit (Issue #572)
[https://avatars.githubusercontent.com/u/189242053?s=20&v=4]jeffrkey left a comment (wmo-im/wmds#572)https://github.com/wmo-im/wmds/issues/572#issuecomment-3000646103
After consultation with others, we are removing "the centre of" from the definition. Not everybody agrees, but it simplifies the definition and make it more consistent with descriptions of measuring a temperature profiles through snow, permafrost, and sea ice in the literature.
— Reply to this email directly, view it on GitHubhttps://github.com/wmo-im/wmds/issues/572#issuecomment-3000646103, or unsubscribehttps://github.com/notifications/unsubscribe-auth/AH2CBSSBFV4J57ULKYTYHKL3FFLHDAVCNFSM6AAAAABVOFXYQWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTAMBQGY2DMMJQGM. You are receiving this because you are subscribed to this thread.Message ID: @.***>
