Preprints
https://doi.org/10.5194/amt-2020-276
https://doi.org/10.5194/amt-2020-276

  14 Sep 2020

14 Sep 2020

Review status: this preprint is currently under review for the journal AMT.

Performance of an open-path near infrared measurement system for measurements of CO2 and CH4 during extended field trials

Nicholas M. Deutscher1, Travis A. Naylor1, Christopher G. R. Caldow1,a, Hamish L. McDougall1, Alex G. Carter1,, and David W. T. Griffith1 Nicholas M. Deutscher et al.
  • 1Centre for Atmospheric Chemistry, School of Earth, Atmospheric and Life Sciences, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW, 2522, Australia
  • anow at: Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, UniversiteParis-Saclay, Gif-sur-Yvette, 91191, France
  • deceased, 8 September 2020

Abstract. Open-path measurements of atmospheric composition provide spatial averages of trace gases that are less sensitive to small-scale variations and the effects of meteorology. In this study we introduce improvements to Open-Path Near Infrared (OP-NIR) Fourier Transform Spectrometer measurements of CO2 and CH4. In an extended field trial, the OP-NIR achieved measurement repeatability six times better for CO2 (0.26 ppm) and ten times better for CH4 (2.0 ppb) over a 1.55 km one-way path than its predecessor. The measurement repeatability was independent of pathlength up to 1.55 km, the longest distance tested. Comparisons to co-located in situ measurements under well-mixed conditions characterise biases of 2.67 % for CO2 and 2.46 % for CH4 relative to in situ measurements calibrated to World Meteorological Organisation – Global Atmosphere Watch (WMO-GAW) scales. The OP-NIR measurements can detect signals due to local photosynthesis and respiration, and local point sources of CH4. The OP-NIR is well-suited for deployment in urban or rural settings to quantify atmospheric composition on kilometre scales.

Nicholas M. Deutscher et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Nicholas M. Deutscher et al.

Nicholas M. Deutscher et al.

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Short summary
This work describes the performance of an open-path measurement system for greenhouse gases in an extended field trial. The instrument obtained measurement repeatability of 0.1 % or better for CO2 and CH4 measurements over a 1.55 km one-way pathway. Comparison to co-located in situ measurements allows characterisation of biases relative to global reference scales. The research was done to show the applicability of the technique and its ability to detect atmospheric-relevant sources and sinks.