ACARS Aircraft Communications Addressing and Reporting System

1. Humidity Measurements by Aircraft of the E-AMDAR FleetTECO 2008Axel HoffDeutscher WetterdienstObserving Networks and DataOffenbach am MainGermany

2. ACARSAircraft Communications Addressing and Reporting System AMDAR = Aircraft Meteorological Data Relay

3. Enroute 20 min after start Sampling rate = 7 min Sampling rate = 50 s Descent beginning at 18000 ft Reports: • Aircraft Identification • Date • Time (UTC) • Position • Altitude (Pressure) • Temperature • Wind Speed • Wind Direction • Water Vapor Mass Mixing Ratio Ascent Sampling rate = 40 s Descent Sampling rate = 10 s until 150 s after start Touch down

4. EUMETNET AMDAR(E-AMDAR) Sampling Points of 24 h over Europe BUFR: DWD (LH) FM 42: SMHI (SAS)Meteo France (AF)UKMO (BA)KNMI (KLM)

5. AMDAR in Numbers (for 2007)

6. Humidity sensor enters the European AMDAR fleet 3 aircraft of the Airbus A320 family Typical daily flight program over Europe: • distance: 300 - 3000 km • up to 6 ascents + descents

7. SpectraSensors, WVSS-II Version 2006 • Infrared Absorption Spectrometer 2f method Tunable Diode Laser • Output: Water Vapor Mass Mixing Ratio Sensor System SEB (System Electronics Box) Hoses for connection Air Sampler with SEB Function Air Sampler Air Sampler Fuselage Sampling Tube 24 cm 24 cm SEB SEB

8. Installation on the Aircraft 4.8 m Exterior View 4 o‘Clock Position Air Sampler

9. Installation on the Aircraft FWD Skin Interior View SEB Outlet Hose, Non-Heated Inlet Hose, Heated Air Sampler Frame

10. Cost Estimate for AMDAR Humidity Profiles

11. Results of the Flight Operation

12. Temperature Dewpoint

15. Verification against COSMO-EU July 200812:00 UTC EU4593 EU5331 EU6564 RMS Bias (Model - Observation)

16. Verification against COSMO-EU September 200812:00 UTC EU4593 EU5331 EU6564 RMSE Bias (Model - Observation)

17. Mixing Ratio (g/kg) RMSE Bias

18. Mixing Ratio (g/kg) RMSE Bias

19. Mixing Ratio (g/kg) RMSE Bias

20. Trial‘s Result of the WVSS-II Version 2006: • Constant routine operation within E-AMDAR • Relative Accuracy within ± 10 % (during the first weeks) • Drift (because of missing Laser Burn-In time) • After a few months of operation: bias of partly 10 to 20 % Rel. Humidity • Limit of detection≈ 0.05 g/kg (80 ppmv) lower 2/3 of the Troposphere • High RMSE because of limited coding in the data link from aircraft to ground

21. Consequences by the manufacturer SpectraSensors Inc.due to the resuls of NOAA / NWS and E-AMDAR / DWD: „Re-engineering“ → WVSS-II Version 2008 leading to • stability in the electronics • tightness of the Laser head • resulting in • - relative accuracy within ± 5 % • - detection limit< 0.015 g/kg (24 ppmv)→ complete Troposphere

22. Planings for further steps • Replacement of the old (2006) WVSS-II units on the Airbus A319 • Separate test flights on research aircraft, such as possibly the Airbus A340 (MOZAIC) - intercomparison sensor on board - WVSS-II house-keeping data - cyclic interchange: aircraft ↔ laboratory • Decision about more sensors • Format improvement for data link from aircraft to ground

23. AMDAR, quo vadis • Expansion and densification of the network on a global level: - inclusion of more airlines, - greater use of night-time starts and landings, - optimizing of the data supply. E-AMDAR / BoM • Aircraft providing additional measurable variables- humidity (to catch up with radiosondes), NWS / NOAA E-AMDAR - geometric altitude (GPS, GLONASS, GALILEO, ...), - air chemistry, aerosols, - turbulence, - icing. • Correction methods for systematic error components. • International standards for aircraft manufacturers: WMO / E-AMDAR - ex-works AMDAR configuration of the on-board software, - ex-works mechanical and electrical precautions for humidity sensor interfaces.

24. Questions or comments?