Important Note: OSCAR/Surface was launched officially on 2 May 2016, thereby replacing WMO No. 9, Volume A, Observing Stations and WMO Catalogue of Radiosondes.

All changes to surface-based observing stations ought now to be made as follows:

• directly by OSCAR/Surface National Focal Points using OSCAR/Surface web interface,
• through Machine to Machine interface between national database of WIGOS metadata and OSCAR/Surface,
• through GAWSIS for Global Atmosphere Watch Stations,
• through JCOMMOPS for marine meteorological and oceanographic observing stations,
• through the WMO Weather Radar Database (WRD) for operational weather radars.

A "legacy" version of Volume A (see below) will continue to be published after 2 May 2016 until the end of 2018. However, the "legacy" format is not 100% compatible with the traditional format described below (see differences below). More detail about this transition can be found in the WWW Operational Newsletter.

• OSCAR/Surface legacy files after 2 May 2016
• Latest version of OSCAR/Surface legacy file
• Differences between OSCAR/Surface legacy file format and Volume A
• Guidance on WIGOS station identifiers