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- Title
Development of a cavity enhanced absorption spectrometer for airborne measurements of CH<sub>4</sub> and CO<sub>2</sub>.
- Authors
O'Shea, S. J.; Bauguitte, S. J.-B.; Gallagher, M. W.; Lowry, D.; Percival, C. J.
- Abstract
High-resolution CH4 and CO2 measurements were made onboard the FAAM BAe 146 UK atmospheric research aircraft during a number of field campaigns. The system was based on an infrared spectrometer using the cavity enhanced absorption spectroscopy technique. Correction functions to convert the mole fractions retrieved from the spectroscopy to dry air mole fractions were derived using laboratory experiments and over a 3 month period showed good stability. Long-term performance of the system was monitored using WMO traceable calibration gases. During the first year of operation (29 flights) analysis of the system's in-flight calibrations suggest that its measurements are accurate to -0.07 ppbv (1σ precision at 1Hz=2.48 ppbv) for CH4 and -0.06 ppmv (1σ precision at 1 Hz=0.66 ppmv) for CO2. The system was found to be very robust, no major motion or altitude dependency could be detected in the measurements. An inter-comparison between whole air samples that were analysed post-flight for CH4 and CO2 by cavity ring down spectroscopy showed a mean difference between the two techniques of -2.4 ppbv (1σ = 2.3 ppbv) for CH4 and -0.22 ppmv (1σ = 0.45 ppmv) for CO2. In September 2012, the system was used to sample biomass burning plumes in Brazil as part of the SAMBBA project (South American biomass burning analysis). From these and simultaneous CO measurements, emission factors for savannah fires were calculated. These were found to be 2.2±0.2 g (kg dry matter)-1 for CH4 and 1710±171 g (kg drymatter)-1 for CO2, which are in excellent agreement with previous estimates in the literature.
- Subjects
ABSORPTION spectra; SPECTROMETERS; AIR pollution; RESEARCH aircraft; CALIBRATION gases
- Publication
Atmospheric Measurement Techniques Discussions, 2013, Vol 6, Issue 1, p1
- ISSN
1867-8610
- Publication type
Article
- DOI
10.5194/amtd-6-1-2013