An aircraft based three channel broadband cavity enhanced absorption spectrometer for simultaneous measurements of NO3, N2O5 and NO2

Atmospheric Measurement Techniques

J. M.Langridge¹  R.Freshwater¹  R.Nightingale¹  R. L.Jones¹  S.Bauguitte¹  J.Sendall¹  O.Norris¹  M. J. S.Daniels¹  M. W.McLeod¹  B.Ouyang¹  C.Ironmonger¹  O. J.Kennedy¹  S. M.Ball¹ 

DOI  :  10.5194/amt-4-1759-2011

学科分类：几何与拓扑

来源: Copernicus Publications

【 摘 要 】

A three channel broadband cavity enhanced absorption spectroscopy (BBCEAS)instrument has been developed for airborne measurements of atmospheric tracegases involved in night-time oxidation chemistry and air quality. Theinstrument was deployed on board the Facility for Airborne AtmosphericMeasurements BAe 146-301 atmospheric research aircraft during the Role ofNighttime Chemistry in Controlling the Oxidising Capacity of the Atmosphere(RONOCO) measurement campaigns between December 2009 and January 2011. Inits present configuration (i.e. specifications of the cavity optics andspectrometers) the instrument is designed to measure NO₃,N₂O₅ (by detection of NO₃ after thermal dissociation ofN₂O₅), H₂O and NO₂ by characterising the wavelengthdependent optical attenuation within ambient samples by molecular absorptionaround 662 nm (NO₃ and H₂O) and 445 nm (NO₂). This paperreports novel advancements in BBCEAS instrumentation including a refinedmethod for performing BBCEAS mirror reflectivity calibrations usingmeasurements of the phase delay introduced by the optical cavities toamplitude modulated radiation. Furthermore, a new methodology is introducedfor fitting the strong but unresolved transitions of water vapour, which isrequired for accurate retrieval of water absorption features from the 662 nmabsorption band used to measure NO₃ concentrations. The paper alsodetails the first example of airborne measurements of NO₃,N₂O₅ and NO₂ over Europe from a flight over the North Sea andThames Estuary on the night of the 20 July 2010, one of the most polluteddays of the RONOCO summertime flying period. As part of this analysis, theperformance of the BBCEAS instrument is assessed by comparing airborneNO₂ measurements to those reported concurrently by a photolyticchemiluminescence based detector.

【 授权许可】

Unknown