1. History, Data Quality, Utility and Display
Aircraft Weather Data
History, Data Quality, Utility and Display

2. Aircraft Weather Data – Outline
A short history of aircraft weather data
Different sources of data from aircraft
Water vapor measurements
Resolution and accuracy
Data utility
Advantages and disadvantages versus other upper air data
Display of data
Future plans

3. Aircraft Weather Data – A Short History
Aircraft have been used as a source of weather data since the dawn of aviation.
In 1904, the United States government began using aircraft to conduct atmospheric research.
Weather instruments on a Navy biplane

4. Aircraft Weather Data – A Short History
In 1931, the Weather Bureau began regular aircraft observations at Chicago, Cleveland, Dallas and Omaha, at altitudes reaching 16,000 feet.
This program replaced weather observations from "kite stations."

5. Aircraft Weather Data – A Short History
In 1937, the first official Weather Bureau radiosonde sounding was made at Boston, Mass.
Weather soundings from aircraft soon ended.

6. Aircraft Weather Data – A Short History
The invention of aircraft data links in the 1970s created renewed interest in using aircraft as weather platforms.
The first automated aircraft weather reports were made in 1979.
ACARS display units in aircraft cockpit

7. Aircraft Weather Data – A Short History
In the 1980's, the Earth Systems Research Laboratory received permission to use aircraft reports in experimental NWP models.
In 1993 ESRL began regular assessment of aircraft data quality. A web based display was developed.
Earth Systems Research Lab

8. Aircraft Weather Data – A Short History
March 20, 1996 the airlines agreed to allow direct access to their data by NWS WFO meteorologists.
Other users now include the FAA, DOD, and universities.
NWS office in Green Bay, Wisconsin

9. Aircraft Weather Data – Different Sources
You may have heard aircraft data referred to as ACARS, MDCRS, AMDAR or TAMDAR.
ACARS (Aircraft Communications, Addressing, and Reporting System) is the name of a datalink service provided by Aeronautical Radio Inc. that sends information between aircraft and ground stations.
MDCRS (Meteorological Data, Collection and Reporting System) is the weather portion of the ACARS data stream.
Aircraft Meteorological DAta Report (AMDAR) is the preferred term by the WMO and NWS.
TAMDAR (Tropospheric AMDAR) is provided by a private company, AIRDAT, using a regional air carrier.

10. Aircraft Weather Data – Different Sources
Eight U.S. Airlines share AMDAR
American
Delta
FEDEX
Mesaba
Northwest
Southwest
United
UPS
The airlines share the cost of down linking the data with the NWS and FAA

11. Aircraft Weather Data – Different Sources
14 Countries now share AMDAR from 2,300 aircraft
Australia, New Zealand, China,
Hong Kong China, Saudi Arabia,
South Africa, United States, Canada,
Netherlands, United Kingdom, France,
Sweden, Hungary, Germany
5 Countries developing AMDAR systems
Chile, Finland, Argentina,
Republic of Korea, and
United Arab Emirates

12. Aircraft Weather Data – Different Sources
The number of observations has increased greatly, and is now over a quarter million per day from around the world!

13. Aircraft Weather Data – Measured Quantities
Nearly all participating AMDAR aircraft report temperature and wind data.
Temperature is determined by the Total Air Temperature sensor, while ground relative winds are computed using an Inertial Navigation System or GPS.
As of 2006, fewer than 10 percent of AMDAR aircraft measured water vapor, turbulence and icing.

14. Aircraft Weather Data – Water Vapor
Measuring water vapor in the upper atmosphere is a difficult task for any sensor.
NWS radiosondes use thin film capacitors to measure relative humidity.
The sensors are relatively inexpensive, but sometimes are prone to errors at very high and very low relative humidity.

15. Aircraft Weather Data – Water Vapor
Studies in the early 1990s showed that relative humidity measurements from commercial aircraft were feasible.
A sensor called the “Water Vapor Sensing System” (WVSS) using a thin film capacitor was installed on six UPS aircraft between 1997 and 1999.
Water Vapor Sensing
System Unit

16. Aircraft Weather Data – Water Vapor
While the WVSS data compared favorably with radiosondes, the
sensors needed to be replaced too frequently to be used on
commercial aircraft.

17. Aircraft Weather Data – Water Vapor
A new sensor (WVSS-II) employs a diode laser to measure water vapor mixing ratio.
WVSS-II was installed on 25 UPS aircraft between 2004 and 2005.
WVSS-II laser diode shown next to a penny, for size comparison purposes.

18. Aircraft Weather Data – Water Vapor
Field studies were conducted
at the Louisville airport
(June 2005, November 2006) to
compare WVSS-II with precision
radiosondes.
A mobile sounding unit from the University of Wisconsin launched radiosondes every three hours during the evening and overnight hours. This was supplemented by interferometer data.
WVSS-II and radiosonde data
within an hour and 50km of each other were compared. Mixing ratio was measured by WVSS-II and relative humidity by the radiosonde.

19. Aircraft Weather Data – Water Vapor
Results from the WVSS-II
and radiosonde comparison
showed an average relative
humidity bias near zero in
the lowest 200hPa and
about 5% above. Standard
deviations are about 5%
below 800hPa and 10%
above.
The accuracy satisfies WMO
requirements for regional
forecast applications.

20. Aircraft Weather Data – Resolution And Accuracy
Much as ASOS, AWOS, DOT and mesonet observations have differences in reporting frequency, accuracy and reliability, so too do reports from aircraft.
Most AMDAR from foreign airlines conform to a WMO reporting standard called ARINC 620. U.S. AMDAR observations generally do not.

21. Aircraft Weather Data – Resolution And Accuracy
ARINC 620 standard provides a data point every 300 feet up to around 850 hPa, then every 1000 feet to cruise altitude.
Most U.S. AMDAR report data at set 1,000-2,000 foot intervals through ascent and descent.
The NWS and WMO are urging U.S. airlines to adopt ARINC 620 standard.

22. Aircraft Weather Data – Resolution And Accuracy
Many studies have been conducted to compare AMDAR to radiosondes, profilers and other upper air data.
They generally show that AMDAR temperatures and winds are slightly superior to those from radiosondes.

23. Aircraft Weather Data – Resolution and Accuracy
A 2001 study by Erik Andersson, Carla Cardinali and Antonio Garcia-Mendez of the ECMWF showed the addition of AMDAR resulted in significant model forecast improvements, all the way out to 7 days.

24. Aircraft Weather Data – Resolution and Accuracy

25. Aircraft Weather Data – Resolution and Accuracy
A study conducted by Ralph Petersen, Geoff Manikin and Dennis Keyser showed that AMDAR contributes significantly to the RUC at all run times.
In fact, the RUC provides little value at asynoptic times without AMDAR – the RUC accuracy declined 20% in the days following September 11, 2001 when air traffic was grounded.

26. Aircraft Weather Data – Forecast Applications
AMDAR data have proven extremely useful in a wide variety of forecast situations, including:
Aviation
Low level wind shear
Ceilings and visibilities
Icing and turbulence
Winter Storms
Precipitation type
Lake effect snow
Thunderstorms
Convective initiation
Calculation of stability indices
Fire Weather
Mixing heights
Haines indices
Relative humidity forecasts
Marine Forecasts
Small craft and Gale Warnings
Hazardous Materials Support
AMDAR can be used to support HAZMAT teams
Can be input into local dispersion models

27. Advantages and Disadvantages
Like any system, AMDAR has advantages and disadvantages.

28. Disadvantages Volume of data may be reduced during large storms.
Most aircraft do not measure water vapor.
AMDAR soundings usually end at 500hPa for regional aircraft, and 250hPa for most others.

29. Advantages
Soundings are not limited to 00UTC and 12UTC. This is important especially during convective season.
Many airports have 10 or more soundings per day (Some large airports have over 100).
AMDAR does not have limiting angles problems like radiosondes.
Inexpensive (AMDAR sounding less than $1 vs. $200 for radiosonde)

30. Aircraft Weather Data – Display Options
AMDAR are available in real-time to the NWS, FAA, and DOD via the ESRL aircraft data web at
AMDAR may also be displayed on AWIPS, via the volume browser.

31. ESRL Aircraft Data
has links to AMDAR data, FAQs, research papers, training materials and more.
Web site has archive of about 3 years of data, allowing for easy retrieval for case studies.
Data can be found at

32. AMDAR Display Options– Web
ESRL web page should allow access to data at all NOAA installations.
Contact Bill Moninger at ESRL regarding access issues. (303)
Data may not be redistributed in real time.

49. Web Display Resources
Additional training on the use of the web page can be found at

50. Future Plans - NWS Support existing AMDAR data network
Expand number of participating regional airlines
Reduce redundant AMDAR soundings at hubs (optimization)
Increase number of water vapor sensors
Let contract for management of water vapor sensing program this year
Deploy 110 units annually through 2010
Reach ~1600 units deployed by 2020

51. Future Plans - WMO Support expansion of AMDAR network
- Assist emerging national AMDAR programs
Provide recommendations for data formats
Provide training and outreach

52. References – History of Aircraft Data
Hughes, P., 1970: A Century of Weather Service,
Gordon and Breech, 212 p.p.
Hughes and Gedzelman, 1995: The New Meteorology.
Weatherwise. 48, 26-36
Moninger, W. R., R. D. Mamrosh, and P. M. Pauley:
Automated Meteorological Reports from
Commercial Aircraft. Bull. Amer. Meteor. Soc., 84,

53. References – Different Sources
Cunning, J., 2000: Commercial Aircraft Provided Weather Data,
Preprints, Fourth Symposium on Integrated Observing Systems,
Long Beach, CA, Amer. Meteor. Soc., 45-48
Moninger, W. R. and P. A. Miller, 1994: ACARS Quality Control,
Monitoring, and Correction. 10th Conference on Numerical Weather
Prediction, Portland, OR, Amer. Meteor. Soc. 1-3

54. References – Resolution and Accuracy
Benjamin, S.G., B.E. Schwartz, and R.E. Cole, 1999: Accuracy of ACARS
wind and temperature observations determined by collocation.
Wea. Forecasting, 14,
Jamison, Brian and William R. Moninger, 2002: An Analysis of the
Temporal and Spatial Distribution of ACARS data in support of the
TAMDAR program. 10th Conf. on Aviation, Range, and Aerospace
Meteorology, Portland, OR, Amer. Meteor. Soc.
Lord, R.J., W.P. Menzel, and L.E. Pecht, 1984: ACARS wind measurements:
An inter-comparison with radiosonde, cloud motion, and VAS thermally
derived winds. J. Atmos. Oceanic Technol., 1,
Morone, L.L., 1986: The observational error of automated wind reports
from aircraft. Bull. Amer. Meteor. Soc., 67,
Schwartz, B. E., and S. C. Benjamin, 1995: A Comparison of Temperature
and Wind Measurements from ACARS-Equipped Aircraft and Rawinsondes.
Wea. Forecasting, 10,

55. Supplemental Slides

56. Aircraft Weather Data – Resolution And Accuracy

57. Aircraft Weather Data – Resolution and Accuracy

58. Aircraft Weather Data – Resolution and Accuracy

59. Aircraft Weather Data – Resolution and Accuracy