AMDAR

AMDAR. The Aircraft Meteorological Data Relay system is a global program coordinated by the World Meteorological Organization for the automated collection and transmission of meteorological data from commercial aircraft during flight. It provides critical upper-air observations of parameters like temperature, wind speed and direction, and turbulence, significantly enhancing the data available for numerical weather prediction models and aviation safety. The system leverages the onboard sensors and avionics of participating airline fleets, creating a cost-effective and high-value component of the World Weather Watch Global Observing System.

Overview

The development of AMDAR was driven by the need to improve the density and frequency of upper-air observations over data-sparse regions, particularly oceans and remote continental areas. Prior to its implementation, primary sources of such data were radiosondes launched from fixed land stations and reports from weather reconnaissance aircraft like those operated by the United States Air Force and NOAA. The program formalized in 1998 under the auspices of the WMO, building upon earlier initiatives such as the Aircraft to Satellite Data Relay system. Key technological enablers were advancements in aircraft air data computer systems, satellite communication links, and standardized data formats, allowing automated reporting without burdening flight crews. This network now provides over 700,000 high-quality observations per day, complementing data from polar-orbiting satellites like the MetOp series and geostationary satellites such as GOES.

Data collection and transmission

Data collection is fully automated, utilizing the aircraft's standard suite of navigation and meteorological sensors. Core measurements are derived from the pitot-static system, inertial reference system, and total air temperature probe. These sensors feed data to the aircraft's flight management system or a dedicated AMDAR avionics unit. The processed meteorological data, typically consisting of wind vector, ambient temperature, pressure altitude, and sometimes humidity from specialized sensors, is then transmitted via VHF data link or satellite communication systems like those provided by Inmarsat or Iridium Communications. The data is routed through ground networks, such as the Aircraft Communications Addressing and Reporting System, to meteorological processing centers like the Meteorological Service of Canada or the UK Met Office, where it undergoes quality control before distribution on the Global Telecommunications System.

Data usage and applications

The primary application of AMDAR data is assimilation into numerical weather prediction models operated by major centers including the European Centre for Medium-Range Weather Forecasts, the National Centers for Environmental Prediction, and the Japan Meteorological Agency. This data improves the accuracy of short-term forecasts, severe weather outlooks, and predictions of atmospheric phenomena like jet stream location and strength. For aviation, the data is crucial for real-time flight planning, providing pilots and dispatchers with accurate information on clear-air turbulence, icing conditions, and winds aloft. It also supports climatological studies by contributing to long-term records of upper-air conditions and validates atmospheric profiles from satellite instruments aboard platforms like Aqua (satellite) and the Suomi NPP.

Participating organizations and programs

The AMDAR program is a collaborative effort involving national meteorological services, airlines, and aircraft manufacturers. Major contributing airlines include United Airlines, Delta Air Lines, Lufthansa, Qantas, and South African Airways. National programs, such as the United States's Tropospheric Airborne Meteorological Data Reporting and Australia's Australian AMDAR, manage fleet participation and data processing. Aircraft manufacturers like Boeing and Airbus integrate the necessary avionics capabilities. Coordination at the international level is managed by the WMO's Aircraft-Based Observing System team, which works with regional bodies like EUMETNET in Europe to standardize practices and expand coverage, including over regions like the Arctic and the South Pacific.

Advantages and limitations

The principal advantages of AMDAR are its high spatial and temporal data density along major flight corridors, its cost-effectiveness by utilizing existing aircraft infrastructure, and the high accuracy of measurements from calibrated aviation sensors. It provides data from the troposphere and lower stratosphere, filling critical gaps between weather radar and satellite observations. However, limitations include geographical bias, with dense data over North America, Europe, and major flight paths but sparse coverage over regions like Africa, South America, and the Southern Ocean. Data is also typically limited to ascent and descent phases and cruise altitude, leaving gaps at other flight levels. Efforts to address these gaps include the development of the Water Vapor Sensing System for humidity and encouraging participation from airlines in underrepresented regions through initiatives led by the WMO and the International Civil Aviation Organization.

Category:Meteorological data and networks Category:Aviation meteorology