Формат METAR: Международный стандарт авиационной метеоинформации

Format for weather reports commonly used in aviation

METAR is a format for reporting weather information. A METAR weather report is predominantly used by aircraft pilots, and by meteorologists, who use aggregated METAR information to assist in weather forecasting. Today, according to the advancement of technology in civil aviation, the METAR is sent as IWXXM model. Raw METAR is the most common format in the world for the transmission of observational weather data. It is highly standardized through the International Civil Aviation Organization (ICAO), which allows it to be understood throughout most of the world.

In its publication the Aeronautical Information Manual, the United States Federal Aviation Administration (FAA) describes the report as aviation routine weather report, while the international authority for the code form, the World Meteorological Organization (WMO), describes it as the aerodrome routine meteorological report. The National Oceanic and Atmospheric Administration (part of the United States Department of Commerce) and the United Kingdom's Met Office both employ the definition used by the FAA. METAR is also known as Meteorological Terminal Aviation Routine Weather Report or Meteorological Aerodrome Report.

METARs typically come from airports or permanent weather observation stations. Reports are generated once an hour or half hour at most stations, but if conditions change significantly at a staffed location, a report known as a special (SPECI) may be issued. Some stations make regular reports more frequently, such as Pierce County Airport (ICAO code: KPLU) which issues reports three times per hour. Some METARs are encoded by automated airport weather stations located at airports, military bases, and other sites. Some locations still use augmented observations, which are recorded by digital sensors, encoded via software, and then reviewed by certified weather observers or forecasters prior to being transmitted. Observations may also be taken by trained observers or forecasters who manually observe and encode their observations prior to transmission.

The METAR format was introduced internationally on 1 January 1968, and has been modified a number of times since. North American countries continued to use a Surface Aviation Observation (SAO) for current weather conditions until 1 June 1996, when this report was replaced with an approved variant of the METAR agreed upon in a 1989 Geneva agreement. The WMO's publication No. 782 "Aerodrome Reports and Forecasts" contains the base METAR code as adopted by the WMO member countries.

A typical METAR contains data for the temperature, dew point, wind direction and speed, precipitation, cloud cover and heights, visibility, and barometric pressure. A METAR may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as a pilot report or PIREP, colour states and runway visual range (RVR). In addition, a short period forecast called a TREND may be added at the end of the METAR covering likely changes in weather conditions in the two hours following the observation. These are in the same format as a Terminal Aerodrome Forecast (TAF). The complement to METARs, reporting forecast weather rather than current weather, are TAFs. METARs and TAFs are used in VOLMET broadcasts.

METAR code is regulated by the World Meteorological Organization in consort with the International Civil Aviation Organization. In the United States, the code is given authority (with some U. S. national differences from the WMO/ICAO model) under the Federal Meteorological Handbook No. 1 (FMH 1), which paved the way for the U. S. Air Force Manual 15 111 on Surface Weather Observations, being the authoritative document for the U. S. Armed Forces. A very similar code form to the METAR is the SPECI. Both codes are defined at the technical regulation level in WMO Technical Regulation No. 49, Vol II, which is copied over to the WMO Manual No. 306 and to ICAO Annex III.

Although the general format of METARs is a global standard, the specific fields used within that format vary somewhat between general international usage and usage within North America. Note that there may be minor differences between countries using the international codes as there are between those using the North American conventions. The two examples which follow illustrate the primary differences between the two METAR variations.