Attn: EPAC SSC Chair Greg Carmichael

Status: APPROVED BY SSC EPAC (5 July 2022

Originators

Jörg Klausen (Chair ET-ACDM), Atsuya Kinoshita (WDCGG), Stoyka Netcheva (WMO)

Background and Rational

GAW traditionally identifies and manages their assets using 3-letter GAW IDs that have been issued and managed by GAWSIS up to now. In the past, it has also been possible to assign such 3-letter GAW IDs to non-GAW stations in GAWSIS, and WDCGG has used these identifiers as their primary identifier. With the advent of WIGOS, WIGOS Station Identifiers WSI have been introduced to uniquely identify stations across all WMO and co-sponsored programs, as well as all other assets managed by OSCAR/Surface. Program-specific identifiers remain in use by many program/networks and GAW is a program that welcomes and relies on contributions from programs/networks with similar objectives that are outside GAW. Some of these programs/networks are considered 'contributing programs/networks'. The concept of program-specific identifiers applies to all of them, but logically, GAW IDs can only be defined for GAW stations (local, mobile, regional and global). Even if/when other programs/networks may resolve to using 3-letter identifiers, these are not formally GAW IDs, because GAW (and through delegation, GAWSIS, now OSCAR/Surface) has no control over their assignment. Strictly speaking, 3-letter GAW IDs are simply GAW-specific identifiers.

Since several WDCs accept data from both, GAW stations and stations affiliated with these other programs/networks, they need to be very careful with labeling station identifiers as GAW IDs. There is a significant risk that a GAW station and another station from another program may use the same 3-letter identifier. As a consequence, WDCs wishing to accept data from non-GAW stations should no longer rely on the assumption that these stations carry a globally unique 3-letter ID. Instead, they should use the globally unique WIGOS Station Identifier managed by OSCAR/Surface. This will align the WDCs with WMO Members’ accepted practices under WIGOS and its WMO wide implementation. There is a clear requirement for any station documented in OSCAR/Surface to obtain a WIGOS Station Identifier and a possibility to document additional program-specific identifiers for a station. While the requirement for registration in OSCAR/Surface of all stations wishing to submit data to a WDC makes perfect sense, the need to assign a 3-letter identifier for stations not qualifying for or interested in obtaining GAW station status clearly does not.

Proposal

The GAW program formally adopts the WIGOS Station Identifiers (WSI) as the primary identifier for GAW stations of all categories (currently: global, regional, local, mobile). The historically used 3-letter GAW IDs are considered to be ancillary program-specific identifiers. As such, the requirement for uniqueness of these identifiers is limited to those stations that are considered GAW stations. The distinction between any 3-letter GAW IDs (= program-specific identifier for GAW stations) and any 3-letter program-specific identifier of a station affiliated to any other program/network is clearly made in the WDCs. [Option to be discussed: Stations wishing to become GAW stations choose a 3-letter GAW ID as part of the registration process.]

Notes

1. WSI are managed within OSCAR/Surface, while program-specific station identifiers are only displayed. Any station - GAW or not - wishing to submit data to a WDC is required to register in OSCAR/Surface according to the rules an procedures explained in the WIGOS Guide.
2. If the assignment of a 3-letter (or any other) GAW ID in addition to the WSI is considered a useful requirement for GAW stations, this must be clearly expressed by the stakeholders, because a central system is needed to managed such lists. In the past, GAWSIS has served as the broker for this.

Implementation timeline

It is expected that WDCs become compliant with the proposal formulated here by end of 2022.

Considerations by ET-ACDM

The proposal was presented by the chair to ET-ACDM during its meeting on 5 May 2022. It was received as non-controversial. The EPAC SSC is requested to 1) endorse the proposal, and 2) to provide feedback to the GAWSIS-OSCAR/Surface Application Board on the need to maintain a broker for 3-letter GAW IDs as program-specific IDs for GAW stations.

Conclusion and Recommendation to EPAC SSC

ET-ACDM members in support of motion:

• Ellsworth J. Welton, Gao Chen, Atsuya Kinoshita, Markus Fiebig, Kjetil Tørseth, John Rimmer, Alex Vermeulen, Jörg Klausen

ET-ACDM members not in support of motion:

• none