This section provides recommended practices for the allocation of issue number and local identifier for Member States and Territories.

Principles for allocating station identifiers

1. Issuers of identifiers are responsible for guaranteeing that no two observing facilities share the same station identifier. Note that the structure of WIGOS station identifiers guarantees that issuers cannot create identifiers that have already been allocated by another issuer.
   1. Issuers of identifiers may choose to use the issue number to allow them to delegate the task of allocating local identifiers to other organizations responsible for managing individual observing networks. Assigning each organization a different issue number will allow those organizations to allocate local identifiers for their observing facilities.
   2. The issuer of identifiers has to record which issue numbers have been allocated and which organization is responsible for managing local identifiers for each.
2. An organization issuing local identifiers (and issue numbers if it has not had one assigned to it) must ensure that no two observing facilities share the same WIGOS station identifier.
   1. When issuing the local identifier:
      1. If the organization is responsible for allocating both issue numbers and local identifiers, it must ensure that no two observing facilities have the same combination of issue number and local identifier.
      2. If the organization is only responsible for allocating local identifiers then it is sufficient for it to ensure that it does not assign the same local identifier to more than one observing facility.
   2. The organization must maintain a record of the local identifiers (and issue numbers) it has allocated (it may choose to use OSCAR for this).
   3. The organization may choose to use an existing national identifier as the local identifier for the observing facility. Doing so in a systematic way may decrease its administrative load.
      1. Historically, station identifiers may have been reused when observing facilities closed and new ones opened. If the organization has been allocated a range of issue numbers, it may wish to consider using different issue numbers to distinguish between the different locations, allowing the local identifier to retain the link to the other location.
      2. Although a single WIGOS station identifier must not be issued to more than one observing facility, it is permitted for a station to have more than one WIGOS station identifier. For example, although all observing facilities with pre-existing World Weather Watch station identifiers have a WIGOS station identifier based on the World Weather Watch identifier, the organization may wish to create a new identifier that is linked to a national numbering scheme.
      3. The WIGOS station identifier for a closed observing facility must not be reused unless the observing facility reopens.
   4. The organization responsible for allocating the WIGOS station identifier should ensure that the operator of the observing facility has committed to providing and maintaining WIGOS metadata for that facility.
      1. In cases where a station has more than one WIGOS station identifier, the organization issuing the local identifier should associate all these station identifiers with the same WIGOS metadata record so that only one WIGOS metadata record needs to be maintained. OSCAR will provide tools to document this linkage.
      2. If a fixed observing facility is moved, the organization should consider whether it should be issued a new WIGOS station identifier, whether the WIGOS metadata should be updated to state that the observing facility at the previous position has closed and whether a new WIGOS metadata record should be created for the new location. The organization must use meteorological judgement on the impacts of the change in deciding whether to retain the WIGOS station identifier or to issue a new one. A move of a few metres is unlikely to be significant, but a move to the opposite side of a mountain would be treated as a new station.
      3. Note: The structure of the WIGOS station identifier means that the range of WIGOS station identifiers is, for practical purposes, unlimited. This removes the need to reuse WIGOS station identifiers.
3. Before issuing a station identifier, search OSCAR/Surface] to make sure that it has not already been allocated.
4. Organizations are strongly advised to document their procedures for allocating WIGOS station identifiers in their quality management system.

Specifying the local identifier

The local identifier may be up to 16 characters long. It must not contain blanks (and any blanks added to the end of the identifier by IT systems must be ignored). The local identifier may contain only lower-case or upper-case Latin letters, numbers or the characters: - (dash), _ (underscore) or . (full stop).

Leading zeroes in a local identifier are significant and must be treated as part of the character string. (Note that this differs from the treatment of leading zeroes in the issuer of identifier and issue number parts of the WIGOS identifier, which are omitted from the WIGOS station identifier.)

Example 1

(a) Consider a Member that has observing systems managed by many different organizations, including the National Meteorological Service (NMS), the National Hydrological Service (NHS) and the National Transport Department. Each of these organizations is independent, and each has its existing conventions for labelling observing facilities. For example, the Meteorological Service uses WMO World Weather Watch station identifiers for its synoptic network, its own numbering system for other weather observing facilities, and another numbering system for its climate observing facilities.

(b) In this situation, the Member (as an issuer of identifiers) might choose to use the following convention for assigning WIGOS station identifiers. In all cases, if an observing facility is closed its local identifier must not be re-attributed (with the same issue number)

Issue Number	Interpretation of Issue Number	Local Identifier
1	NMS synoptic observing facility	WMO World Weather Watch station identifier (with leading zeroes if necessary to make it five characters long). Initially, to ensure that plotting software can display local identifiers, the Member chooses to limit their length to five characters and to assign to new WIGOS stations identifiers that lie outside the block of identifiers allocated to the Member by the World Weather Watch.
2	NMS other weather observing facility	Existing national station identifier (with leading zeroes if necessary). The local identifier for a new observing facility is created using the existing procedures for national station identifiers.
3	NMS climate observing facility	Existing climate station identifier (without leading zeroes, as that was the convention for climate observing facility identifiers in the past). New observing facilities are allocated identifiers using the existing practices.
100-200	Used by NHS for allocating identifiers for its observing facilities. The NHS allocates one number to each of its regions. The NHS is organized according to river basins, and it uses its range of issue numbers to subdelegate the allocation of local identifiers to each river basin authority.	The NHS uses its existing river basin observing facility numbering system.
1000-10000	Used by the National Transport Department for allocating its observing facility identifiers. Each road has its own issue number.	Derived from the distance of travel along a road when travelling away from the national capital before reaching the observing facility.

Example 2

(a) A Member has implemented a national system for managing its national assets. Each
observing facility has to be registered on this system and as a consequence has been
allocated an asset number used to track all information about the facility. Some of these
assets are mobile platforms (such as moored buoys). Disposable observing platforms (such
as radiosondes) are associated with the asset number of their base station.

(b) The Member wishes to align its WIGOS station identifiers with its national asset
management system. It chooses to use the national asset number as the local identifier.
The Member is concerned that it may move assets from one location to another. In
consequence, the Member uses the issue number to record changes in location. Because it
wishes to record past positions as well, it decides initially to use an issue number of 10000
and to increment it for an asset every time that asset is re-deployed. It uses issue numbers
less than 10000 to record historical positions for that asset. By doing this, the Member
ensures that the asset number will not result in misleading WIGOS metadata histories and
the link to the asset number will be maintained.