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Weather Station Identifiers

Identifiers are an important building block in meteorology because they provide a scheme which identifies the various weather stations in use. To accurately use weather data, meteorologists and climatologists have a vested interest in the identifiers used by weather stations. Unfortunately the system is not as simple as it should be. Not only are newer identifiers are constantly coming online, being modified, or made obsolete, but identifiers are sometimes brought into use without coordination between agencies. This is a major problem for those of us who are exchanging weather information in our increasingly globalized world. This resource is intended to help meteorologists maintain accurate station listings.

1. Master Station Identifier Database (MSID)

Weather Graphics has recently begun publishing the Master Station Identifier Database (MSID). This is a list of about 41,000 worldwide station identifiers which harmonizes thousands of ICAO, FAA, WMO, WBAN, and special use identifiers, and standardizes place names according to ISO 3166 guidelines. It now includes integration of the latest FAA, ICAO, and WMO identifiers, making it the most up-to-date database available anywhere. On the same token, it also includes numerous historical stations, which are regrettably omitted from many government databases (such as closed airports and CAA airfields). Weather Graphics started developing the MSID in 2006 to meet the rigorous standards required by some of our historical database work and to use in our future projects. We found that most comprehensive sources like MASLIB, NCDC, and ISH are greatly outdated and contained a number of minor errors, and as a result were not adequate.

The MSID is available as a spreadsheet free of charge, providing it is not used for any commercial purpose without advance written permission.
    master-location-identifier-database.xls (Database, Excel, Version 1.0.0, 9/1/2010, 17 MB)
    master-location-identifier-database.txt (Database, Tab delimited text file, Version 1.0.0, 9/1/2010, 6 MB)
    master-location-identifier-database.pdf (Documentation, PDF, 150 KB)

Suggestions, comments, and corrections are greatly appreciated and will be acknowledged. You may send these to our contact page.

2. An overview of identifier schemes

Identifiers were developed at the turn of the 20th century with the rise of telegraph, teletype, and radio communication stations. This allowed stations to be identified precisely using only simple call letters. With the rise of computing power in the mid 20th century, identifiers also entered use in weather data processing and storage. Listed here are the identifier schemes used in meteorology and aviation weather:

1. World Meteorological Organization (WMO) identifier. The WMO identifier scheme was developed in the early 20th century, comprising one of the oldest location identifier schemes. It relies on a 5-digit numeric code to identify a weather station. It is widely used in synoptic ("6-hourly") weather reports and upper air reports. The entire identifier is often called the "index number". The first two digits are sometimes referred to as the "block number" and refer to the geographic area (00-29 Europe, 30-59 Asia, 60-68 Africa, 69 special use, 70-79 North America, 80-89 South America, 90-99 Oceania). The last three digits are loosely referred to as the "station number" in the context of "block numbers". The WMO provides free access to all WMO identifier assignments on its website.

2. International Civil Aviation Organization (ICAO) Location Indicator. The ICAO location indicator consists of 4-letter identifiers approved for use under the International Civil Aviation Administration plan of identifiers. In our MLID list above, we categorically prohibit WSR-88D radars from possessing an ICAO or FAA code, because this causes conflicts. For example, KGRK commonly refers to both an aerodrome and a radar site, when in fact they are separated by 35 miles. The ICAO, publishes all ICAO identifiers in Location Indicators, ICAO Publication 7910, with prices ranging from $180 to $920.

3. Federal Aviation Administration (FAA) Location Identifiers. The FAA location identifier (FAA LID) is a three-digit (sometimes 4-digit alphanumeric) designator. The Civil Aeronautics Administration began publishing three-letter identifiers starting in the 1940s. These were mostly for teletype use and did not start appearing in planning documents for pilots until the mid-1960s. Use of the FAA LID ceased for meteorological purposes in 1996, but it is still widely used for aeronautical purposes in the U.S. In many cases, a three-digit identifier can be "converted" to its ICAO form by adding the appropriate ICAO region letter as the first letter. However this is NOT a reliable rule, especially in Alaska and Hawaii. While ANC may translate correctly to PANC, there are many stations where this is not the case, such as BRW, which is PABR under the ICAO form. This is a significant source of errors in some crossreference tables. An example of an FAA identifier is "DFW" for Dallas-Fort Worth International Airport. The FAA publishes assignments in Location Identifiers, FAA Publication FAAO 7350. Coordinates are published in the National Flight Database (NFD), which costs about $180.

4. Weather Bureau Army Navy (WBAN) identifier. In the 1950s and 1960s, computer programmers with the NWS found that it was difficult to work with weather data because some observations were transmitted with FAA LIDs, some were transmitted with WMO station indexes, and other data on paper had no number at all. The WBAN scheme was developed, which was one of the first large-scale efforts to standardize identifiers. A WBAN identifier is a 5-digit identifier, similar in appearance to the WMO identifier but not equivalent. It is still used by NCDC to identify many of its climatological datasets and continues to be very important for meteorological work. NCDC provides free access to all known WBAN identifier assignments.

5. Master Station Library (MASLIB) Catalog Number. The MASLIB scheme was developed in the 1960s by Air Force Global Weather Center (AFGWC), now part of Air Force Weather Agency (AFWA). It was created to overcome shortfalls in the WBAN system, which is geared mostly for climatology, and assist AFGWC/AFWA with routing and processing data in real-time. AFGWC/AFWA has maintained the MASLIB for over 40 years, though public releases ceased after 1999, presumably because of increased concerns with operations security. The MASLIB code consists of 6 numerical digits, and is heavily based on the WMO identifier. In fact, if an identifier has a WMO assignment, its MASLIB number will be the WMO identifier suffixed with zero. Even if a station does not have a WMO identifier, it will have a MASLIB number very similar to that of neighboring stations that do have a WMO identifier.

6. Environment Canada location identifier. Canada bases their identifiers heavily on the FAA Location Identifier scheme, adopting primarily identifiers starting with Y but also some starting with W, X, and Z. They are assigned by Transport Canada and Environment Canada. Canada has rapidly expanded some of its mesonets and has begun using identifiers starting with other parts of the alphabet, posing the question of possible conflicts in the near future.

7. International Air Transport Association Identifier. The IATA identifier is a 3-letter code that identifies a specific worldwide airport. It is generally used by the airline industry for ticketing, baggage. IATA identifiers are not generally used in meteorology. The IATA charges $346 to $1100 for direct access to its catalogue of IATA identifier assignments.

3. Problems with crossreferencing.

Meteorologists, and to a certain extent, pilots, all have to be aware of pitfalls and other issues arising from the multiple identifier schemes that are in use today.

1. Uprooting. Identifiers are not permanently fixed to a location and are sometimes "moved" by government officials, a process known as uprooting. This is an especially serious problem because any person using products from many years ago or trying to analyze climatological information may end up with erroneous results. In the U.S., minor identifiers are commonly retired for 20 or 30 years and then assigned to a new location. This in itself causes little trouble. However, overnight uprooting of major airports does occur from time to time. Prominent examples are the movement of "DEN" from Stapleton to DIA and the movement of "AUS" from Mueller Airport to Bergstrom Field. Analysts have to know start and end dates for identifiers, and these are not always available from sources.

2. Inadequate documentation. There are deficiencies in the station lists caused by poorly documented station locations. The latter is especially a problem with ICAO identifiers.

3. KQ identifiers. The KQ-- ICAO identifier block is reserved by the U.S. Department of Defense for special use. Some of the identifiers have been assigned for routine use and their information is known (such as KQCU for Fort Chaffee and KQWS for Fort Drum; many are listed in this source). Other identifiers are used for (1) classified operating locations and (2) for deployed combat weather teams. Their association with a geographic location is usually classified or marked for official use only.

4. Weather stations are not necessarily at airports and may be in weather "observatories". This is common in countries like the former USSR. Unfortunately the WMO listings often fail to identify where in a community a weather station is, and this is compounded by imprecise location coordinates. As a result, some aggregated identifier listings may erroneously place a site at the nearest airfield. Also, some of the "guessed" locations in older MASLIB sources are based on town locations and may not represent the actual location.

5. Romanization is a common problem plaguing station listings, especially when older or inconsistent systems are used.

4. Public (free) station identifier resources

1. NOTAMS ICAO lookup is run by the Department of Defense flight planning authority and incorporates nearly all ICAO information.

2. NCDC Station Locator is a good source of U.S. station information, but it seems to be running about 2 years behind on updates as it misses a lot of the ASOS stations; I have also noticed a few errors here and there. The raw station inventories can be found here (raw directory listing), along with a massive station history flatfile called MASTER-STN-HIST.TXT (32 MB). (Due to size, archive copy is not kept on this server; we will put one online if NCDC ever goes down).

3. NCDC Multinetwork Metadata List is another decent government source that includes WBAN numbers. It seems to lack a lot of the newer ASOS stations and may have originated from the same database as NCDC Station Locator.

4. NOAA's Platform Name list is helpful for making sense of offshore identifiers.

5. NWS/TG Table contains thorough listings but from unknown sources and for an unknown purpose. (Also see table with K--- identifiers sorted by identifier).

6. NWS Meteorological Station Information Lookup is the National Weather Service's "public" station database. While the interface is promising, its data is outdated and it does not contain many of the newer ASOS sites. This is probably simply a web interface for the flatfile above (NSD.TXT).

7. Greg Thompson (NCAR/RAP) Station Table is very good and updated often! It is a must-see. An older version is mirrored at the FAA ADDS Weather site. Note that there is no provision for older stations and it appears that the distinction is blurred between FAA and IATA identifiers.

8. NWS Data Review Group processes and archives Requests for Change to its various datastreams (NWSTG, NOAAPORT, FOS, NWWS, AWIPS, AFOS). Identifier changes can sometimes be found in these documents. (AS OF 2009 THIS APPEARS TO HAVE BEEN PASSWORD PROTECTED)

9. NWS Systems Operations Center Change Notices are another source for finding new identifiers by combing through datastream changes to the NWSTG system.

10. METEO France is another exhaustive database of stations (no position info). A backup copy (dated 8 Jan 1999, retrieved 25 May 2009) is archived here.

11. ECCAIRS Location Indicators list by the European Coordination Centre for Accident and Incident Reporting Systems appears to be an authoritative derivation of ICAO Pub 7910 and thus provides a valuable supplementary source of ICAO identifiers. Unfortunately it has not been updated since January 2006. An archival copy is made available here.

12. NAV CANADA's TAF Interface is about the only "official" source of Canada's METAR identifier information online. This is a crude way of obtaining a few of some of the more obscure ones.

13. Environment Canada's Synoptic Station List shows synoptic identifiers within Canada, in WMO Pub 9 A format (thanks to Christine Hudnall for finding the new version). A backup copy (dated May 2009, retrieved 25 May 2009) is archived here.

14. British Atmospheric Data Centre Historical International Station Catalogue Historical International Station Catalogue - This index is somewhat outdated and similar to the MASLIB, but due to the historical slant I have found this useful for researching identifier changes, especially outside the U.S. It can be used in conjunction with a similar NCDC product. A backup copy (dated 3 Nov 1998, retrieved 25 May 2009) is archived here (1.8 MB).

15. British Atmospheric Data Centre Historical International Station Catalogue Historical International Station Catalogue - This index is somewhat outdated and similar to the MASLIB, but due to the historical slant I have found this useful for researching identifier changes, especially outside the U.S. It can be used in conjunction with a similar NCDC product. A backup copy (dated 3 Nov 1998, retrieved 25 May 2009) is archived here (1.8 MB).

16. Philip Gladstone's CWOP - This I have found useful for researching is pretty thorough and has many different weather databases crossreferenced. You can also check this list. The problems with this list is it omits various WMO and WBAN identifiers and does not have historical identifier information.

17. AIRNAV is a high-traffic aviation website that is useful for finding exact information about any airfield. It has been of use for finding new airfields with obscure ICAO / FAA identifiers.

18. World Aero Data is another good aviation identifier site. It appears it draws mostly on the withdrawn DAFIF product.

19. OpenFlights is a collaborative attempt to pick up where DAFIF left off. One problem with this project is the blurring of IATA and FAA identifiers, which in meteorological use can cause numerous conflicts with historical data.

5. Other investigation resources.

1. LatLonToElevation allows fast calculation of unknown elevations using the National Elevation Dataset and Shuttle Radar Topography Mission.

2. METAR Maintenance, a short page by Joe Wakefield, describes what is involved in updating AWIPS with new stations.

3. Country codes. This interface to geonames.org determines which country a given lat/long is in.

4. Place. This interface to geonames.org determines which place represents a given lat/long.

5. Time zones. To find the time zone used by a particular station, we recommend using the geonames.org database. Here is a convenient form for requesting data.

6. Elevation. This interface to geonames.org queries the SRTM (Shuttle Radar Topographic Mission) and returns an elevation in meters. However we've found that the Google Earth elevation readout gives considerably more accurate results, at least in the U.S. and Canada.