Abstract
Abstract. High-resolution CH4 and CO2 measurements were made on board the FAAM BAe-146 UK (Facility for Airborne Atmospheric Measurements, British Aerospace-146) 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 (World Meteorological Office) 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 1.28 ppb (1σ repeatability at 1 Hz = 2.48 ppb) for CH4 and 0.17 ppm (1σ repeatability at 1 Hz = 0.66 ppm) for CO2. The system was found to be 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 ppb (1σ = 2.3 ppb) for CH4 and −0.22 ppm (1σ = 0.45 ppm) 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 dry matter)−1 for CO2, which are in excellent agreement with previous estimates in the literature.
Highlights
SystemsAirborne Atmospheric Measurements, British Aerospace146) atmospheric research aircraft during a number of field campaigns
This paper describes the development of a system for CO2 and CH4 measurements on board the FAAM BAe146 UK (Facility for Airborne Atmospheric Measurements, British Aerospace-146) atmospheric research aircraft using the cavity-enhanced absorption spectroscopy technique (CEAS)
CEAS and similar spectroscopic techniques are claimed as an absolute measurement approach, allowing mole fractions to be determined for specific gas molecules without the need for calibration
Summary
Airborne Atmospheric Measurements, British Aerospace146) atmospheric research aircraft during a number of field campaigns. Advancements in instrument technology to allow routine and rapid measurement of greenhouse gases to the necessary WMO specifications have been made for ground-based networks Operating such instruments on airborne platforms usually requires significant modification and understanding of environmental impacts on instrument performance and more frequent calibrations to meet these same specifications. This paper describes the development of a system for CO2 and CH4 measurements on board the FAAM BAe146 UK (Facility for Airborne Atmospheric Measurements, British Aerospace-146) atmospheric research aircraft using the cavity-enhanced absorption spectroscopy technique (CEAS) This system has been used during a number of recent airborne field projects.
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