AMDAR (aircraft meteorological data relay)

Investigation of the data quality of AMDAR aircraft data

The weather station is always on board!

Each aircraft carries "pitot tubes" (P) to measure the speed at which the air is flowing past the aircraft ("airspeed"). For the conversion, the ambient air pressure is measured at a "static port" (S). Knowledge of both "airspeed" and the speed of the aircraft above the ground - determined by a global positioning system (GPS) allows to calculate the wind speed. Along with navigation instruments, all modern passenger aircraft carry temperature sensors (T). Their measurements are needed for navigation and for controlling the engines. Occasionally, these measurements are announced during flight by the pilots.

Fig 1: Meteorological instrumentation of an Airbus A319 (letters, see text)

AMDAR system

Many aircraft report the measurements taken on board by data radio (ACARS) to their airline. The airlines then forward the data to their national weather service. From the German airlines, Lufthansa takes part in AMDAR and transmits data to the German Weather Service (DWD). Since the cost is for only about 1% of the cost of a radiosonde ascent, the World Meteorological Organisation (WMO) strongly promotes the program. The radiosonde measurements are to be supplemented or even partially replaced by AMDAR.

Three-dimensional data

Because planes transmit most data during takeoff and landing, they effectively yield vertical soundings of the atmosphere. The data reported by the aircraft, hence, resemble the soundings by radiosondes ("weather balloon", Figure 2).

Fig. 2: Examplary data for one day (15.Jan 2005) over Europe. The color indicates the altitude of data points.

Research for AMDAR

The characteristics of the AMDAR data are still little explored. For example: what are the measurement errors? Can AMDAR help to predict turbulence and weather fronts? Therefore, we are currently investigating the systematic deviations between AMDAR and other measurements and model systems, respectively (see Figure 3).

Fig. 3: