Aircraft-based observations

Aircraft-based observations (ABO) are measurements of the atmosphere made from an aircraft platform. They provide information on air temperature, wind speed and direction, air pressure and, on suitably equipped aircraft, humidity and turbulence, among other environmental variables. Transmitted in real time to National Meteorological Services (NMHS) with the support of the aviation industry, these measurements enhance numerical weather forecasting systems, strengthen early warnings systems, support climate monitoring and drive safer, more cost-effective aviation operations.

What do aircraft measure?

Most modern commercial aircraft are already equipped with sensors and systems that measure meteorological variables for navigation and aircraft performance monitoring. These measurements can also be used for weather diagnosis and forecasting. Variables that are not measured by default generally require an additional sensor.  Meteorological data can also be derived directly from existing air traffic control systems.

As participating aircraft take off and land, observations are collected at successive heights. Together, these can generate a vertical profile: a picture of how conditions change at different levels of the atmosphere. At busy airports, participating flights can provide profiles hourly or more frequently, helping forecasters follow changes throughout the day. They also report conditions along their routes at cruising altitude, helping to diagnose and forecast hazardous phenomena such as icing and turbulence. Each observation includes its time, location and altitude, allowing it to be placed accurately within the atmosphere.  

Aircraft temperature and wind measurements are comparable in quality to those from radiosondes carried by weather balloons up to 12,000 metres above the surface. The two sources complement each other: radiosondes reach higher altitudes in the stratosphere, while aircraft provide more frequent profiles around busy airports in the upper troposphere/lower stratosphere.

How are observations collected and shared?

WMO works with its Members and aviation partners to make aircraft observations available for meteorological use through the WMO ABO Programme, a subsystem of the WMO Integrated Global Observing System, a key programme component of the expanded World Weather Watch. This cooperation involves NMHSs, partner airlines, air navigation service providers, civil aviation agencies, the International Air Transport Association and the International Civil Aviation Organization.

Much of this data is collected through the Aircraft Meteorological Data Relay (AMDAR), a WMO-led observing system operated by NMHSs in cooperation with participating airlines. AMDAR relies mainly on existing aircraft sensors, onboard computers and communications systems, requiring minimal additional investment.

Specialized software selects and processes the measurements, then sends reports to the ground through radio or satellite links supported by data link service providers. Meteorological services receive the observations, check their quality and share them in near-real time through the WMO Information System used for international exchange of weather, climate and water information. Monitoring data quality can also alert airlines to possible faults in aircraft sensors or systems. 

Better forecasts and early warnings

Numerical weather prediction uses mathematical models to predict how the atmosphere is likely to change. This requires an accurate picture of current conditions as the starting point. Aircraft observations help provide that picture, particularly for temperature and wind at cruising levels and through the layers sampled during ascent and descent.

The WMO Guide to Aircraft-based Observations reports reductions of 10–20% in numerical weather prediction forecast error over the first 24 hours from the use of AMDAR and other aircraft observations. An impact study also showed that, in data-sparse regions such as South America, a major increase in AMDAR observations made aircraft data the most influential source of observations in the forecasting system tested, accounting for more than 27% of the reduction in short-range forecast error.

Forecasters also use the observations to check and update forecasts between model runs. Frequent profiles help them monitor the development of thunderstorms, fog and low cloud, track changes in wind and assess the likelihood of rain, snow or freezing rain. These data support public and marine forecasts as well as early warnings of hazardous weather.

Safer and more efficient aviation

Better measurements and forecasts of wind, temperature, humidity and turbulence help airlines plan routes, choose flight levels and respond to changing weather. It can reduce unplanned diversions, delays and fuel use, supporting more economical operations and lower carbon dioxide emissions.

Aircraft observations help identify wind shear, a rapid change in wind speed or direction over a short distance, which can be particularly hazardous during take-off and landing. Observations also support forecasts of turbulence, poor visibility and ice build-up on aircraft.

Automated turbulence reports provide objective information about how rough or smooth conditions are. Sharing these observations helps pilots and operations staff anticipate or avoid turbulence and reduce risks to passengers and crew.  

Climate and environmental monitoring

Beyond daily weather forecasting, aircraft observations contribute to climate data archives, climate monitoring and prediction, and research into changes in the atmosphere. Wind and temperature profiles also help scientists and forecasters assess how smoke and air pollution spread.

Research programmes can use additional instruments aboard passenger aircraft to measure atmospheric composition. One example is the In-service Aircraft for a Global Observing System, which collects observations of trace gases, present in small concentrations, and aerosols.  

Expanding coverage and capabilities

The WMO ABO Programme brings together an expanding range of observing systems. Alongside conventional AMDAR, these include meteorological data transmitted or derived from air traffic management systems, third-party aircraft observing systems, research aircraft and weather uncrewed aircraft systems (UAS) such as drones and other remotely piloted aircraft.

More than 895,000 aircraft-based observations are now provided each day through 12 operational national and regional programmes working with around 43 participating airlines. Combining observations from different aircraft and aviation systems is helping to extend coverage, including in data-sparse regions such as Africa and South America.

UAS could help extend this coverage further, particularly in parts of the lower atmosphere where observations remain limited. A WMO demonstration campaign involving 44 operators in 13 countries conducted more than 13,000 flights, demonstrating their potential to fill important observational gaps while meeting WMO accuracy requirements for temperature, humidity and wind. WMO is now working to support their wider integration into operational observing systems.