While the WMO AMDAR Observing System is the chief source of aircraft-based observations on the GTS, other aircraft-based observations are derived from several sources including:
•
PIlot REPorts ( PIREP ),
•
AIRcraft REPorts ( AIREP ) and
• Automatic Dependent Surveillance Contract ( ADS-C )
Data can also be derived from commercially operated observing systems, such as the Panasonic TAMDAR system or the FlyHt AFIRS system, which may be available on the GTS depending contractual arrangements.
A ircraft M eteorological Da ta R elay (AMDAR) was conceived to take advantage of the ever expanding fleet of commercial aircraft populating our skies, by turning them into mobile data recorders. The system provides benefits due to the fact that commercial aircraft operate over large parts of the world and often where ground based recording system may not be viable and current data collection may be sparse.
The most recent AMDAR system is ACARS (Aircraft
Communication Addressing and Reporting) this software records measurements made by the aircrafts own instrumentation and then uses the built in communication devices (VHF, HF or SATCOM) to transmit the measurements to the data acquisition systems, they are subsequently quality controlled and inserted into the WMO Global
Telecommunication System (GTS) for use in global NWP models.
The data transmitted from the aircraft consists of two main parts, the first being the positional and operational information of the aircraft;
 Aircraft identifier
 Latitude, and Longitude;

Time;

Phase of flight;
The second being the observed meteorological data including;
 Height (pressure derived)
 Temperature
 Wind speed
 Wind direction
Additional parameters reported by some aircraft
– Turbulence, Humidity
– Icing is a potential parameter
The observations from the AMDAR systems provide high quality data at the aircrafts cruising altitude (made during the level flight phase), or in turn provide a vertical profile up to the cruising altitude (made during the ascent and descent phases of the flight). The resolution of AMDAR observations meets the accuracy requirements for global numerical weather prediction (NWP).
However because the systems makes use of commercial aircraft certain limitations exist, such as the irregularity of observation times due to flight schedules, and vertical profile data only generally being available in terminal areas, this does however make AMDAR every useful for airfield forecasting.
The European contribution to the worldwide AMDAR coverage comes from the EUMETNET component E-AMDAR, managed on behalf of Members by Met Office Observations.
European E-AMDAR Coverage (24hour period)
Worldwide E-AMDAR Coverage (24hour period)
Worldwide Coverage (24hour period)
Currently E-AMDAR has retrofitted 3 aircraft from the
Lufthansa Airbus A319 fleet with water vapour sensors
(WVSS-II) which integrate with the ACARS systems to provide humidity measurements, comparable to that obtained by Radiosondes.
E-AMDAR humidity Coverage (72hour period)
WVSS-II Sensor
The initial 3 sensors are being upgraded and a further 6 new sensors are to be installed by the end of 2014. Operational trials of these sensors are being used to develop the business case for investment for a possible implementation of up to
100 units of a European ABO humidity network.
In addition, Met Office is collaborating with Panasonic (PAC) on their TAMDAR programme. In Europe 100+ sensors, which report humidity, are to be installed on the Flybe fleet of aircraft.
Data is only available for R&D at present! TAMDAR sensor
A large number of commercial aircraft broadcast their position and movement for use by air traffic management.
This information can be collected by third parties and converted into wind and temperature observations.
There is an ongoing project within Observations to begin the collection of this data using a network of our own receivers.
Currently we have two systems operating, one at the Exeter
HQ in the carpark which has been collecting data since the summer 2013 and another at Thurnham radar site (east of
London). The Exeter receiver has provided information for up to 40000 wind observations per hour.
Current UK Met Office coverage (3 hour period)
The map above shows the lowest observation per 0.125° square during 3 hours from both receivers. The lowest altitude (0 m) is red and the highest in blue (13000 m). The black triangles show major airports, the approach and departure tracks for several of these can easily be seen in the altitude data.
A single aircraft profile over south Wales
The image shows a single profile from an aircraft observed from the Exeter receiver flying over south Wales. The black data is the observed Mode-S observations and the red the
UKV model background interpolated to the same locations and times as the Mode-S data. There is good agreement between the model and observations. Work is ongoing to further understand the biases associated with this data but for wind observations the errors appear to be similar to
AMDAR.
Data is soon to be incorporated into a test metdb in anticipation of some initial assimilation trials and the deployment of further UK receiver sites is being planned.