Overview of Camborne, UK and Jungfraujoch, Switzerland Field Campaigns

1. Overview of Camborne, UK and Jungfraujoch, Switzerland Field Campaigns CAVIAR Annual Meeting 15th Dec 2009, Abingdon Marc Coleman, Tom Gardiner, Nigel Swann (NPL) Liam Tallis (University of Reading) Stuart Newman, Jonathan Taylor (Met Office) Paul Green, Ralph Beeby, Juliet Pickering (Imperial College) + FAAM team

2. Background • Field measurements of water vapour continuum required to help validate modelling work • Key instruments radiometrically calibrated at NPL prior to each measurements campaign • Two instruments for airborne measurements (mounted on the FAAM BAe146 aircraft) • One instrument for ground-based measurements • Two measurement campaigns carried out • Camborne, UK: Low altitude – wet • Jungfraujoch, Switzerland: High altitude – dry • Carried out at high and low altitude sites so that it is possible to access the centre of water bands, which facilitates characterisation of the dependence of the continuum on water abundance

3. Key Instruments(1): TAFTS and ARIES TAFTS – tropospheric airborne Fourier transform spectrometer • Both instruments passive Fourier transform infrared (FTIR) spectrometers • TAFTS (Imperial College) • Measures difference spectrum between nadir and zenith views • 4 internal black bodies. One warm and one cold for each view • ARIES (Met Office) • Can measure nadir and zenith (not a difference measurement) • Internal black bodies ARIES – airborne research interferometer evaluation system

4. Key Instruments(2): NPLs High Resolution FTIR Solar tracker • Instrument is a Bruker IFS125M FTIR augmented with NPL optics • Unlike TAFTS and ARIES system is active • Uses sun as a light source • Interfaced with a solar tracker to track sun • Capable of resolutions of up to 0.0035 cm-1 • Broad spectral coverage

5. Radiometric Calibration of TAFTS & ARIES CAVIAR Black Body (CBB) • TAFTS and ARIES calibrated using a custom built black body – CAVIAR Black Body (CBB) • -80 to +40°C temp. range • Traceable to the primary radiometer (method by which the Candela is realised in the UK) TAFTS Grooves for ethanol coolant

6. Radiometric Calibration of NPL FTIR • For active FTIR use NPLs ultra high temperature black body • ~3000K • Used to realise the primary radiance scale in the UK • Traceable to the primary radiometer (as is the CBB) • All three instruments traceable, therefore have comparability

7. Facility for Airborne Atmospheric Measurements (FAAM) • After calibration TAFTS & ARIES re-installed on FAAM plane for first CAVIAR field trial • Also on-board: • Chilled mirror dew point • Total water Lyman- • Fluorescence water vapour sensor • SAW hygrometer • CVI hygrometer • dropsondes

8. Camborne Field Trial • August – September 2008 • FAAM flew out of Cranfield base • NPL FTIR & Reading MICROTOPS (aerosol optical thickness) based at Camborne Met Office site • Other relevant instrumentation at Camborne • Routine sonde launches from Camborne at 11:15 and 23:15 U.T. • Additional launches made on ‘good’ measurement days • GPS water vapour column • Laser cloud base and visibility • Surface dew point Sonde launch NPL FTIR

9. FAAM Flights over Camborne • South east inaccessible due to military operations • Operated mainly starting from north and west • Allowed runs at low level over sea providing surface temperature and emissivity data • Runs of 40 nautical miles lasted ~10min at 10,000 feet • Polygon FAAM accents (“balloon chasing”) will allow comparison between sonde and FAAM water vapour measurements

10. Camborne Water Vapour Profiles • Aircraft straight and level runs divided into three sections: Camborne and northern and southern areas over ocean • (Corrected) radiosonde and dropsonde profiles were used as the nearest coincident measurements of temperature and water vapour • ECMWF analysis and forecast fields were used to account for changes in air mass with time and distance, allowing the sonde profiles to be modified accordingly • Similar process is being undertaken for the Jungfraujoch measurements

11. = aborted flight = successful flight Camborne Flights • A typically “British” summer! • On 22nd Aug a double flight was possible, although throughout the day broken cloud caused occasional obstruction • However, 18th Sep saw excellent clear sky conditions, hence so far analysis has focussed on this day • nb. silver lining to fewer flights than planned was that additional flights were available for the Jungfraujoch field trial

12. Eiger Mönch FAAM in Basel Jungfrau Jungfraujoch research station (NPL FTIR) Jungfraujoch Field Trial • NPL FTIR (1.8 tonne of equipment!) transported to Jungfraujoch research station (~3500m above sea level) • FAAM plane based in Basel

13. FAAM Flights • Used glacier on approach for uniform surface temperature and emissivity measurements • Runs at 15,000 to 35,000 feet • Spiral ascents over the Jungfrau • Dropsondes from a high level

14. Jungfraujoch Research Station • NPL FTIR & MICROTOPS installed at research station. Solar tracker mounted on balcony to face south looking down valley • Other data available from the station • Liege FTIR (part of NDACC) • LIDAR (unfortunately v.little coincidence with flights) • Sonde launches from Payerne • GPS water vapour

15. Example Effect of High Altitude • Camborne and Jungfraujoch spectra from NPL FTIR show effect of measuring from high altitude

16. = aborted flight = successful flight Jungfraujoch Flights • 9 flights, compared to 3 in Camborne, justified spending the summer out of Britain! • Sonde launch from Payerne on evening of 20th Jul • Will allow for comparison against FAAM instruments • MetOp overpass on morning of 27th Jul • Dates when there was the most coincident air- and ground-based measurements with the smallest amount of cloud interruption were • 19th, 26th, 27th Jul and 4th Aug • Analysis initially to focus on 27th July as measurement conditions very good (i.e. very clear) and coincides with MetOp overpass

17. Summary • Achieved traceable, radiometric calibration of TAFTS, ARIES and NPL FTIR • Custom built CAVIAR BB will be available for future calibrations • Two successful field trials at a low and high altitude sites • Bad weather days in Camborne off-set with better than expected weather in Jungfruajoch. So overall we posses a large body of data • Have identified key days from each field trial for focussed analysis • Instrument intercomparison • In support of modelling work