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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 9, issue 8
Atmos. Meas. Tech., 9, 3527–3546, 2016
https://doi.org/10.5194/amt-9-3527-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Meas. Tech., 9, 3527–3546, 2016
https://doi.org/10.5194/amt-9-3527-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 03 Aug 2016

Research article | 03 Aug 2016

Assessment of errors and biases in retrievals of XCO2, XCH4, XCO, and XN2O from a 0.5 cm–1 resolution solar-viewing spectrometer

Jacob K. Hedelius1, Camille Viatte2, Debra Wunch2,a, Coleen M. Roehl2, Geoffrey C. Toon3,2, Jia Chen4,b, Taylor Jones4, Steven C. Wofsy4, Jonathan E. Franklin5,c, Harrison Parker6, Manvendra K. Dubey6, and Paul O. Wennberg2 Jacob K. Hedelius et al.
  • 1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
  • 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
  • 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 4School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
  • 5Department of Physics & Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
  • 6Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA
  • anow at: Department of Physics, University of Toronto, Toronto, Ontario, Canada
  • bnow at: Electrical and Computer Engineering, Technische Universität München, Munich, Germany
  • cnow at: School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA

Abstract. Bruker™ EM27/SUN instruments are commercial mobile solar-viewing near-IR spectrometers. They show promise for expanding the global density of atmospheric column measurements of greenhouse gases and are being marketed for such applications. They have been shown to measure the same variations of atmospheric gases within a day as the high-resolution spectrometers of the Total Carbon Column Observing Network (TCCON). However, there is little known about the long-term precision and uncertainty budgets of EM27/SUN measurements. In this study, which includes a comparison of 186 measurement days spanning 11 months, we note that atmospheric variations of Xgas within a single day are well captured by these low-resolution instruments, but over several months, the measurements drift noticeably. We present comparisons between EM27/SUN instruments and the TCCON using GGG as the retrieval algorithm. In addition, we perform several tests to evaluate the robustness of the performance and determine the largest sources of errors from these spectrometers. We include comparisons of XCO2, XCH4, XCO, and XN2O. Specifically we note EM27/SUN biases for January 2015 of 0.03, 0.75, –0.12, and 2.43 % for XCO2, XCH4, XCO, and XN2O respectively, with 1σ running precisions of 0.08 and 0.06 % for XCO2 and XCH4 from measurements in Pasadena. We also identify significant error caused by nonlinear sensitivity when using an extended spectral range detector used to measure CO and N2O.

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Portable FTS instruments with lower resolution are being used to measure gases (including CO2, CH4, CO, and N2O) in the atmosphere. We compared measurements from four of these instruments for a few weeks, and with one for nearly a year to a higher resolution TCCON standard. We also performed tests to assess performance under different atmospheric and instrumental conditions. We noted consistent offsets in the short-term (~1 month); more research is still needed to assess precision longer term.
Portable FTS instruments with lower resolution are being used to measure gases (including CO2,...
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