Testing and evaluation of a new airborne system for continuous N 2O, CO 2, CO, and H 2O measurements: the Frequent Calibration High-performance Airborne Observation System (FCHAOS)

Gvakharia, Alexander; Kort, Eric A.; Smith, Mackenzie L.; Conley, Stephen

We present the development and assessment of a new flight system that uses a commercially available continuous-wave, tunable infrared laser direct absorption spectrometer to measure inline-formulaN2O, inline-formulaCO2, CO, and inline-formulaH2O. When the commercial system is operated in an off-the-shelf manner, we find a clear cabin pressure–altitude dependency for inline-formulaN2O, inline-formulaCO2, and CO. The characteristics of this artifact make it difficult to reconcile with conventional calibration methods. We present a novel procedure that extends upon traditional calibration approaches in a high-flow system with high-frequency, short-duration sampling of a known calibration gas of near-ambient concentration. This approach corrects for cabin pressure dependency as well as other sources of drift in the analyzer while maintaining a inline-formula∼90 % duty cycle for 1 Hz sampling. Assessment and validation of the flight system with both extensive in-flight calibrations and comparisons with other flight-proven sensors demonstrate the validity of this method. In-flight 1inline-formulaσ precision is estimated at 0.05 ppb, 0.10 ppm, 1.00 ppb, and 10 ppm for inline-formulaN2O, inline-formulaCO2, CO, and inline-formulaH2O respectively, and traceability to World Meteorological Organization (WMO) standards (1inline-formulaσ) is 0.28 ppb, 0.33 ppm, and 1.92 ppb for inline-formulaN2O, inline-formulaCO2, and CO. We show the system is capable of precise, accurate 1 Hz airborne observations of inline-formulaN2O, inline-formulaCO2, CO, and inline-formulaH2O and highlight flight data, illustrating the value of this analyzer for studying inline-formulaN2O emissions on inline-formula∼100 km spatial scales.

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Gvakharia, Alexander / Kort, Eric A. / Smith, Mackenzie L. / et al: Testing and evaluation of a new airborne system for continuous N2O, CO2, CO, and H2O measurements: the Frequent Calibration High-performance Airborne Observation System (FCHAOS). 2018. Copernicus Publications.

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