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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/amt-2020-170
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2020-170
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  08 May 2020

08 May 2020

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This preprint is currently under review for the journal AMT.

Validation of XCO2 and XCH4 retrieved from a portable Fourier transform spectrometer with those from in-situ profiles from aircraft borne instruments

Hirofumi Ohyama1, Isamu Morino1, Voltaire A. Velazco2,3, Theresa Klausner4, Gerry Bagtasa5, Matthäus Kiel6, Matthias Frey1, Akihiro Hori1, Osamu Uchino1, Tsuneo Matsunaga1, Nicholas Deutscher2, Joshua P. DiGangi7, Yonghoon Choi7, Glenn S. Diskin7, Sally E. Pusede8, Alina Fiehn4, Anke Roiger4, Michael Lichtenstern4, Hans Schlager4, Pao K. Wang9, Charles C.-K. Cho9, Maria Dolores Andrés-Hernández10, and John P. Burrows10 Hirofumi Ohyama et al.
  • 1National Institute for Environmental Studies, Tsukuba, Japan
  • 2Centre for Atmospheric Chemistry, University of Wollongong, NSW 2522, Australia
  • 3Oscar M. Lopez Center for Climate Change Adaptation and Disaster Risk Mgmt. Foundation Inc., Manila, Philippines
  • 4Deutsches Zentrum für Luft-und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 5Institute of Environmental Science & Meteorology, University of the Philippines, Diliman Quezon City, Philippines
  • 6NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 7NASA Langley Research Center, Hampton, VA, USA
  • 8Department of Environmental Sciences, University of Virginia, Charlottesville, VA, USA
  • 9Research Center for Environmental Changes Academia Sinica, Taipei, Taiwan
  • 10Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany

Abstract. Column-averaged dry-air mole fractions of carbon dioxide (XCO2) and methane (XCH4) measured by a solar viewing portable Fourier transform spectrometer (FTS, EM27/SUN) have been characterized and validated by comparison using in-situ profile measurements made during the transfer flights of two aircraft campaigns: Korea-United States Air Quality Study (KORUS-AQ) and Effect of Megacities on the Transport and Transformation of Pollutants on the Regional and Global Scale (EMeRGe). The aircraft flew over two Total Carbon Column Observing Network (TCCON) sites: Rikubetsu, Japan (43.46° N, 143.77° E) for the KORUS-AQ campaign and Burgos, Philippines (18.53° N, 120.65° E) for the EMeRGe campaign. The EM27/SUN was deployed at the corresponding TCCON sites during the overflights. The mole fraction profiles obtained by the aircraft over Rikubetsu differed between the ascending and the descending flights above approximately 8 km for both CO2 and CH4. Because the spatial pattern of tropopause heights based on potential vorticity values from the ERA5 reanalysis show that the tropopause height over the Rikubetsu site was consistent with the descending profile, we used only the descending profile to compare with the EM27/SUN data. Both the XCO2 and XCH4 derived from the descending profiles over Burgos were lower than those from the ascending profiles. Output from the Weather Research and Forecast Model indicate that higher CO2 for the ascending profile originated in central Luzon, an industrialized and densely populated region about 400 km south of the Burgos TCCON site. Air masses observed with the EM27/SUN overlap better with those from the descending aircraft profiles than those from the ascending aircraft profiles with respect to their properties such as origin and atmospheric residence times. Consequently, the descending aircraft profiles were used for the comparison with the EM27/SUN data. The EM27/SUN XCO2 and XCH4 data were derived by using the GGG2014 software in which air mass independent correction factors utilized for the TCCON data (0.9898 for XCO2 and 0.9765 for XCH4) were not applied. The comparison of the EM27/SUN observations with the aircraft data revealed that on average, the EM27/SUN XCO2 data were biased low by 1.22 % and the EM27/SUN XCH4 data were biased low by 1.67 %. The resulting air mass independent correction factors of 0.9878 for XCO2 and 0.9833 for XCH4 were obtained for the portable FTS.

Hirofumi Ohyama et al.

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Hirofumi Ohyama et al.

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Short summary
Column-averaged dry-air mole fractions of CO2 and CH4 measured by a solar viewing portable Fourier transform spectrometer (EM27/SUN) were validated with in-situ profile data obtained during the transfer flights of two aircraft campaigns. Atmospheric dynamical properties based on ERA5 and WRF-Chem were used as criteria for selecting the best aircraft profiles for the validation. The resulting air mass independent correction factors for the EM27/SUN data were 0.9878 for CO2 and 0.9833 for CH4.
Column-averaged dry-air mole fractions of CO2 and CH4 measured by a solar viewing portable...
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