References

AMT

Atmospheric Measurement Techniques

AMT

Atmos. Meas. Tech.

1867-8548

Copernicus Publications

Göttingen, Germany

10.5194/amt-6-1257-2013

Evaluation of a new JMA aircraft flask sampling system and laboratory trace gas analysis system

Tsuboi

¹ Matsueda

¹ Sawa

¹ Niwa

¹ Nakamura

² Kuboike

² Saito

² Ohmori

² Iwatsubo

² Nishi

² Hanamiya

² Tsuji

² Baba

Geochemical Research Department, Meteorological Research Institute, Tsukuba, Japan

Japan Meteorological Agency, Tokyo, Japan

15 05 2013

6 5 1257 1270

2013

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

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The full text article is available as a PDF file from https://amt.copernicus.org/articles/6/1257/2013/amt-6-1257-2013.pdf

We established and evaluated a flask air sampling system on a cargo C-130H aircraft, as well as a trace gas measurement system for the flask samples, as part of a new operational monitoring program of the Japan Meteorological Agency (JMA). Air samples were collected during each flight, between Kanagawa Prefecture (near Tokyo) and Minamitorishima (an island located nearly 2000 km southeast of Tokyo), from the air-conditioning system on the aircraft. Prior to the operational employment of the sampling system, a quality assurance test of the sampled air was made by specially coordinated flights at a low altitude of 1000 ft over Minamitorishima and comparing the flask values with those obtained at the surface. Based on our storage tests, the flask samples remained nearly stable until analyses. The trace gas measurement system has, in addition to the nondispersive infrared (NDIR) and vacuum ultraviolet resonance fluorescence (VURF) analyzers, two laser-based analyzers using wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) and off-axis integrated cavity output spectroscopy (ICOS). Laboratory tests of the laser-based analyzers for measuring flask samples indicated relatively high reproducibility with overall precisions of less than ±0.06 ppm for CO2, ±0.68 ppb for CH4, ±0.36 ppb for CO, and ±0.03 ppb for N2O. Flask air sample measurements, conducted concurrently on different analyzers were compared. These comparisons showed a negligible bias in the averaged measurements between the laser-based measurement techniques and the other methods currently in use. We also estimated that there are no significant isotope effects for CH4, CO and N2O using standard gases with industrial isotopic compositions to calibrate the laser-based analyzers, but CO2 was found to possess isotope effects larger than its analytical precision.

References 1

Akimoto, H.: Global air quality and pollution, Science, 302, 1716–1719, <a href="http://dx.doi.org/10.1126/science.1092666">https://doi.org/10.1126/science.1092666</a>, 2003.

Allison, C. E. and Francey, R. J.: Verifying Southern Hemisphere trends in atmospheric carbon dioxide stable isotopes, J. Geophys. Res., 112, D21304, <a href="http://dx.doi.org/10.1029/2006JD007345">https://doi.org/10.1029/2006JD007345</a>, 2007.

Baer, D. S., Paul, J. B., Gupta, M., and O'Keefe, A.: Sensitive absorption measurements in the near-infrared region using off-axis integrated-cavity-output spectroscopy, Appl. Phys. B, 75, 261–265, <a href="http://dx.doi.org/10.1007/s00340-002-0971-z">https://doi.org/10.1007/s00340-002-0971-z</a>, 2002.

Bergamaschi, P., Frankenberg, C., Meirink, J. F., Krol, M., Villani, M. G., Houweling, S., Dentener, F., Dlugokencky, E. J., Miller, J. B., Gatti, L. V., Engel, A., and Levin, I.: Inverse modelling of global and regional CH4 emissions using SCIAMACHY satellite retrievals, J. Geophys. Res., 114, D22301, <a href="http://dx.doi.org/10.1029/2009JD012287">https://doi.org/10.1029/2009JD012287</a>, 2009.

Brenninkmeijer, C. A. M., Crutzen, P., Boumard, F., Dauer, T., Dix, B., Ebinghaus, R., Filippi, D., Fischer, H., Franke, H., Frieß, U., Heintzenberg, J., Helleis, F., Hermann, M., Kock, H. H., Koeppel, C., Lelieveld, J., Leuenberger, M., Martinsson, B. G., Miemczyk, S., Moret, H. P., Nguyen, H. N., Nyfeler, P., Oram, D., O'Sullivan, D., Penkett, S., Platt, U., Pupek, M., Ramonet, M., Randa, B., Reichelt, M., Rhee, T. S., Rohwer, J., Rosenfeld, K., Scharffe, D., Schlager, H., Schumann, U., Slemr, F., Sprung, D., Stock, P., Thaler, R., Valentino, F., van Velthoven, P., Waibel, A., Wandel, A., Waschitschek, K., Wiedensohler, A., Xueref-Remy, I., Zahn, A., Zech, U., and Ziereis, H.: Civil Aircraft for the regular investigation of the atmosphere based on an instrumented container: The new CARIBIC system, Atmos. Chem. Phys., 7, 4953–4976, <a href="http://dx.doi.org/10.5194/acp-7-4953-2007">https://doi.org/10.5194/acp-7-4953-2007</a>, 2007.

Chen, H., Winderlich, J., Gerbig, C., Hoefer, A., Rella, C. W., Crosson, E. R., Van Pelt, A. D., Steinbach, J., Kolle, O., Beck, V., Daube, B. C., Gottlieb, E. W., Chow, V. Y., Santoni, G. W., and Wofsy, S. C.: High-accuracy continuous airborne measurements of greenhouse gases (CO2 and CH4) using the cavity ring-down spectroscopy (CRDS) technique, Atmos. Meas. Tech., 3, 375–386, <a href="http://dx.doi.org/10.5194/amt-3-375-2010">https://doi.org/10.5194/amt-3-375-2010</a>, 2010.

Chen, H., Karion, A., Rella, C. W., Winderlich, J., Gerbig, C., Filges, A., Newberger, T., Sweeney, C., and Tans, P. P.: Accurate measurements of carbon monoxide in humid air using the cavity ring-down spectroscopy (CRDS) technique, Atmos. Meas. Tech., 6, 1031–1040, <a href="http://dx.doi.org/10.5194/amt-6-1031-2013">https://doi.org/10.5194/amt-6-1031-2013</a>, 2013.

Crosson, E. R.: A cavity ring-down analyzer for measuring atmospheric levels of methane, carbon dioxide, and water vapor, Appl. Phys. B-Lasers O., 92, 403–408, <a href="http://dx.doi.org/10.1007/s00340-008-3135-y">https://doi.org/10.1007/s00340-008-3135-y</a>, 2008.

Dlugokencky, E. J., Myers, R. C., Lang, P. M., Masarie, K. A., Crotwell, A. M., Thoning, K. W., Hall, B. D., Elkins, J. W., and Steele, L. P.: Conversion of NOAA atmospheric dry air CH4 mole fractions to a gravimetrically prepared standard scale, J. Geophys. Res., 110, D18306, <a href="http://dx.doi.org/10.1029/2005JD006035">https://doi.org/10.1029/2005JD006035</a>, 2005.

Gerbig, C., Smitgen, S., Kley, D., Volz-Thomas, A., Dewey, K., and Haaks, D.: An improved fast-response vacuum-UV resonance fluorescence CO instrument, J. Geophys. Res., 104, 1699–1704, <a href="http://dx.doi.org/10.1029/1998JD100031">https://doi.org/10.1029/1998JD100031</a>, 1999.

Gregg, J. S., Andres, R. J., and Marland, G.: China: Emissions pattern of the world leader in CO2 emissions from fossil consumption and cement production, Geophs. Res. Lett., 35, L08806, <a href="http://dx.doi.org/10.1029/2007GL032887">https://doi.org/10.1029/2007GL032887</a>, 2008.

Hall, B. D., Dutton, G. S., and J. W. Elkins, J. W.: The NOAA nitrous oxide standard scale for atmospheric observations, J. Geophys., Res., 112, D09305, <a href="http://dx.doi.org/10.1029/2006JD007954">https://doi.org/10.1029/2006JD007954</a>, 2007.

Hammer, S., Konrad, G., Vermeulen, A. T., Laurent, O., Delmotte, M., Jordan, A., Hazan, L., Conil, S., and Levin, I.: Feasibility study of using a "travelling" CO2 and CH4 instrument to validate continuous in-situ measurement stations, Atmos. Meas. Tech. Discuss., 5, 7141–7185, <a href="http://dx.doi.org/10.5194/amtd-5-7141-2012">https://doi.org/10.5194/amtd-5-7141-2012</a>, 2012.

Huang, J., Golombek, A., Prinn, R., Weiss, R., Fraser, P., Simmonds, P., Dlugokencky, E. J., Hall, B., Elkins, J., Steele, P., Langenfelds, R., Krummel, P., Dutton, G., and Porter, L.: Estimation of regional emissions of nitrous oxide from 1997 to 2005 using multinetwork measurements, a chemical transport model, and an inverse method, J. Geophys., Res., 113, D17313, <a href="http://dx.doi.org/10.1029/2007JD009381">https://doi.org/10.1029/2007JD009381</a>, 2008.

Ishijima, K., Sugawara, S. Kawamura, K., Hashida, G., Morimoto, S., Murayama, S., Aoki, S., and Nakazawa, T.: Temporal variations of the atmospheric nitrous oxide concentration and its δ15N and δ18O for the latter half of the 20th century reconstructed from firn air analyses, J. Geophys. Res., 112, D03305, <a href="http://dx.doi.org/10.1029/2006JD007208">https://doi.org/10.1029/2006JD007208</a>, 2007.

Jacob, D. J., Crawford, J. H., Kleb, M. M., Connors, V. S., Bendura, R. J., Raper, J. L., Sachse, G. W., Gille, J. C., Emmons, L., and Heald, C. L.: Transport and chemical evolution over the Pacific (TRACE-P) aircraft mission: Design, execution, and first results, J. Geophys. Res., 108, 9000, <a href="http://dx.doi.org/10.1029/2002JD003276">https://doi.org/10.1029/2002JD003276</a>, 2003.

Karion, A., Sweeney, C., Tans, P., and Newberger, T.: AirCore: An Innovative atmospheric sampling system, J. Atmos. Ocean. Tech., 27, 1839–1853, <a href="http://dx.doi.org/10.1175/2010JTECHA1448.1">https://doi.org/10.1175/2010JTECHA1448.1</a>, 2010.

Karion, A., Sweeney, C., Wolter, S., Newberger, T., Chen, H., Andrews, A., Kofler, J., Neff, D., and Tans, P.: Long-term greenhouse gas measurements from aircraft, Atmos. Meas. Tech., 6, 511–526, <a href="http://dx.doi.org/10.5194/amt-6-511-2013">https://doi.org/10.5194/amt-6-511-2013</a>, 2013.

Kato, S., Akimoto, H., Bräunlich, M., Röckmann, T., and C. A. M. Brenninkmeijer, C. A. M.: Measurements of stable carbon and oxygen isotopic compositions of CO in automobile exhausts and ambient air from semi-urban Mainz, Germany, Geochem. J., 33, 73–77, 1999.

Liang, Q., Jaeglé, L., Jaffe, D. A., Weiss-Penzias, P., Heckman, A. and Snow, J. A.: Long-range transport of Asian pollution to the northeast Pacific: Seasonal variations and transport pathways of carbon monoxide, J. Geophys., Res., 109, D23S07, <a href="http://dx.doi.org/10.1029/2003JD004402">https://doi.org/10.1029/2003JD004402</a>, 2004.

Machida, T., Kita, K., Kondo, Y., Blake, D., Kawakami, S., Inoue, G., and Ogawa, T.: Vertical and meridional distributions of the atmospheric CO2 mixing ratio between northern midlatitudes and southern subtropics, J. Geophys. Res., 108, 8401, <a href="http://dx.doi.org/10.1029/2001JD000910">https://doi.org/10.1029/2001JD000910</a>, 2003.

Machida, T., Matsueda, H., Sawa, Y., Nakagawa, Y., Hirotani, K., Kondo, N., Goto, K., Nakazawa, T., Ishikawa, K., and Ogawa, T.: Worldwide measurements of atmospheric CO2 and other trace gas species using commercial airlines, J. Atmos. Ocean. Tech., 25, 1744–1754, <a href="http://dx.doi.org/10.1175/2008JTECHA1082.1">https://doi.org/10.1175/2008JTECHA1082.1</a>, 2008.

Marenco, A., Thouret, V., Nédélec, P., Smit, H., Helten, M., Kley, D., Karcher, F., Simon, P., Law, K., Pyle, J., Poschmann, G., Von Wrede, R., Hume, C., and Cook, T.: Measurement of ozone and water vapor by Airbus in-service aircraft: The MOZAIC airborne program, An overview, J. Geophys. Res., 103, 25631–25642, <a href="http://dx.doi.org/10.1029/98JD00977">https://doi.org/10.1029/98JD00977</a>, 1998.

Matsueda, H. and Inoue, H. Y.: Measurements of atmospheric CO2 and CH4 using a commercial airliner from 1993 to 1994, Atmos. Environ., 30, 1647–1655, <a href="http://dx.doi.org/10.1016/1352-2310(95)00374-6">https://doi.org/10.1016/1352-2310(95)00374-6</a>, 1996.

Matsueda, H., Inoue, H. Y., Sawa, Y., Tsutsumi, Y., and Ishii, M.: Carbon monoxide in the upper troposphere over the western Pacific between 1993 and 1996, J. Geophys. Res., 103, 19093–19110, <a href="http://dx.doi.org/10.1029/98JD01598">https://doi.org/10.1029/98JD01598</a>, 1998.

Matsueda, H., Inoue, H. Y., and Ishii, M.: Aircraft observation of carbon dioxide at 8–13 km altitude over the western Pacific from 1993 to 1999, Tellus, 54B, 1–21, <a href="http://dx.doi.org/10.1034/j.1600-0889.2002.00304.x">https://doi.org/10.1034/j.1600-0889.2002.00304.x</a>, 2002.

Matsueda, H., Sawa, Y., Wada, A., Inoue, H. Y., Suda, K., Hirano, Y., Tsuboi, K., and Nishioka, S.: Methane standard gases for atmospheric measurements at the MRI and JMA and intercomparison experiments, Pap. Meteorol. Geohys., 54, 91–109, <a href="http://dx.doi.org/10.2467/mripapers.54.91">https://doi.org/10.2467/mripapers.54.91</a>, 2004.

Murayama, S., Harada, K., Gotoh, K., Kitao, T., Watai, T., and Yamamoto, S.: On large variations in atmospheric CO2 concentration observed over the central and western Pacific Ocean, J. Geophys. Res., 108, 4243, <a href="http://dx.doi.org/10.1029/2002JD002729">https://doi.org/10.1029/2002JD002729</a>, 2003.

Murayama, S., Takamura, C., Yamamoto, S., Saigusa, N., Morimoto, S., Kondo, H., Nakazawa, T., Aoki, S., Usami, T., and Kondo, M.: Seasonal variations of atmospheric CO2, δ13C, and δ18O at a cool temperate deciduous forest in Japan: Influence of Asian monsoon, J. Geophys. Res., 115, D17304, <a href="http://dx.doi.org/10.1029/2009JD013626">https://doi.org/10.1029/2009JD013626</a>, 2010.

Nakazawa, T., Morimoto, S., Aoki, S., and Tanaka, M.: Time and space variations of the carbon isotopic ratio of tropospheric carbon dioxide over Japan, Tellus, 45B, 258–274, <a href="http://dx.doi.org/10.1034/j.1600-0889.1993.t01-2-00004.x">https://doi.org/10.1034/j.1600-0889.1993.t01-2-00004.x</a>, 1993.

Nara, H., Tanimoto, H., Tohjima, Y., Mukai, H., Nojiri, Y., Katsumata, K., and Rella, C. W.: Effect of air composition (N2, O2, Ar, and H2O) on CO2 and CH4 measurement by wavelength-scanned cavity ring-down spectroscopy: calibration and measurement strategy, Atmos. Meas. Tech., 5, 2689–2701, <a href="http://dx.doi.org/10.5194/amt-5-2689-2012">https://doi.org/10.5194/amt-5-2689-2012</a>, 2012.

Niwa, Y., Machida, T., Sawa, Y., Matsueda, H., Schuck, T. J., Brenninkmeijer, C. A. M., Imasu, R., and Satoh, M.: Imposing strong constraints on tropical terrestrial CO2 fluxes using passenger aircraft based measurements, J. Geophys. Res., 117, D11303, <a href="http://dx.doi.org/10.1029/2012JD017474">https://doi.org/10.1029/2012JD017474</a>, 2012.

Novelli, P. C., Masarie, K. A., Lang, P. M., Hall, B. D., Myers, R. C., and Elkins, J. W.: Reanalysis of tropospheric CO trends: Effects of the 1997–1998 wildfires, J. Geophys. Res., 108, 4464, <a href="http://dx.doi.org/10.1029/2002JD003031">https://doi.org/10.1029/2002JD003031</a>, 2003.

Richardson, S. J., Miles, N. L., Davis, K. J., Crosson, E. R., Rella, C. W., and Andrews, A. E.: Field testing of cavity ring-down spectroscopy analyzers measuring carbon dioxide and water vapor, J. Atmos. Ocean. Tech., 29, 397–406, <a href="http://dx.doi.org/10.1175/JTECH-D-11-00063.1">https://doi.org/10.1175/JTECH-D-11-00063.1</a>, 2012.

Sawa, Y., Matsueda, H., Makino, Y., Inoue, H. Y., Murayama, S., Hirota, M., Tsutsumi, Y., Zaizen, Y., Ikegami, M., and Okada, K.: Aircraft observation of CO2, CO, O3 and H2 over the North Pacific during PACE-7 campaign, Tellus, 56B, 2–20, <a href="http://dx.doi.org/10.1111/j.1600-0889.2004.00088.x">https://doi.org/10.1111/j.1600-0889.2004.00088.x</a>, 2004.

Sawa, Y., Tanimoto, H., Yonemura, S., Matsueda, M., Mukai, H., Wada, A., Taguchi, S., Hayasaka, T., Tsuruta, H., Tohjima, Y., Mukai, H., Kikuchi, N., Katagiri, S., and Tsuboi, K.: Carbon monoxide for widespread pollution events observed over the western North Pacific during EAREX campaign 2005, J. Geophys. Res., 112, D22S26, <a href="http://dx.doi.org/10.1029/2006JD008055">https://doi.org/10.1029/2006JD008055</a>, 2007.

Sawa, Y., Machida, T., and Matsueda, H.: Aircraft observations of the seasonal variation in the transport of CO2 in the upper atmosphere, J. Geophys. Res., 117, D05305, <a href="http://dx.doi.org/10.1029/2011JD016933">https://doi.org/10.1029/2011JD016933</a>, 2012.

Schuck, T. J., Brenninkmeijer, C. A. M., Slemr, F., Xueref-Remy, I., and Zahn, A.: Greenhouse gas analysis of air samples collected onboard the CARIBIC passenger aircraft, Atmos. Meas. Tech., 2, 449–464, <a href="http://dx.doi.org/10.5194/amt-2-449-2009">https://doi.org/10.5194/amt-2-449-2009</a>, 2009.

Smith, A. D., Barone, G. A., Higgins, M. E., Kendall, B. R. F., and Lavrich, D. J.: Method for chemical vapor deposition of silicon on to substrates for use in corrosive and vacuum environments, United States Patent No.7, 070, 833B2, 2006.

Snover, A. K., Quay, P. D., and Hao, W. M.: The D/H content methane emitted from biomass burning, Global Biogeochem. Cy., 14, 11–24, <a href="http://dx.doi.org/10.1029/1999GB900075">https://doi.org/10.1029/1999GB900075</a>, 2000.

Stephens, B. B., Gurney, K. R., Tans, P. P., Sweeney, C., Peters, W., Bruhwiler, L. M., Ciais, P., Ramonet, M., Bousquet, P., Nakazawa, T., Aoki, S., Machida, T., Inoue, G., Vinnichenko, N., Lloyd, J., Jordan, A., Heimann, M., Shibistova, O. B., Langenfelds, R. L., Steele, L. P., Francey, R. J., and Denning, A. S.: Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO2, Science, 316, 1732–1735, <a href="http://dx.doi.org/10.1126/science.1137004">https://doi.org/10.1126/science.1137004</a>, 2007.

Stephens, B. B., Miles, N. L., Richardson, S. J., Watt, A. S., and Davis, K. J.: Atmospheric CO2 monitoring with single-cell NDIR-based analyzers, Atmos. Meas. Tech., 4, 2737–2748, <a href="http://dx.doi.org/10.5194/amt-4-2737-2011">https://doi.org/10.5194/amt-4-2737-2011</a>, 2011.

Terao, Y., Mukai, H., Nojiri, Y., Machida, T., Tohjima, Y., Saeki, T., and Maksyutov, S.: Interannual variability and trends in atmospheric methane over the western Pacific from 1994 to 2010, J. Geophys. Res., 116, D14303, <a href="http://dx.doi.org/10.1029/2010JD015467">https://doi.org/10.1029/2010JD015467</a>, 2011.

Tohjima, Y., Machida, T., Utiyama, M., Katsumata, M., Fujimura, Y., and Maksyutov, S.: Analysis and presentation of in situ atmospheric methane measurements from Cape Ochi-ishi and Hateruma Island, J. Geophys. Res., 107, 4148, <a href="http://dx.doi.org/10.1029/2001JD001003">https://doi.org/10.1029/2001JD001003</a>, 2002.

Tohjima, Y., Katsumata, K., Morino, I., Mukai, H., Machida, T., Akama, I., Amari, T., and Tsunogai, U.: Theoretical and experimental evaluation of the isotope effect of NDIR analyzer on atmospheric CO2 measurement, J. Geophys. Res., 114, D13302, <a href="http://dx.doi.org/10.1029/2009JD011734">https://doi.org/10.1029/2009JD011734</a>, 2009.

Tsunogai, U., Nakagawa, F., Komatsu, D. D., and Gamo, T.: Stable carbon and oxygen isotopic analysis of atmospheric carbon monoxide using continuous-flow isotope ratio MS by isotope ratio monitoring of CO, Anal. Chem., 74, 5695–5700, <a href="http://dx.doi.org/10.1021/ac020290x">https://doi.org/10.1021/ac020290x</a>, 2002.

Umezawa, T., Aoki, S., Nakazawa, T., and Morimoto, S.: A high-precision measurement system for carbon and hydrogen isotopic ratios of atmospheric methane and its application to air samples collected in the western Pacific region, J. Meteor. Soc. Jpn., 87, 365–379, <a href="http://dx.doi.org/10.2151/jmsj.87.365">https://doi.org/10.2151/jmsj.87.365</a>, 2009.

Wada, A., Sawa, Y., Matsueda, H., Taguchi, S., Murayama, S., Okubo, S., and Tsutsumi, Y.: Influence of continental air mass transport on atmospheric CO2 in the western North Pacific, J. Geophys. Res., 112, D07311, <a href="http://dx.doi.org/10.1029/2006JD007552">https://doi.org/10.1029/2006JD007552</a>, 2007.

Wada, A., Matsueda, H., Sawa, Y., Tsuboi, K., and Okubo, S.: Seasonal variation of enhancement ratios of trace gases observed over 10 years in the western North Pacific, Atmos. Environ, 45, 2129–2137, <a href="http://dx.doi.org/10.1016/j.atmosenv.2011.01.043">https://doi.org/10.1016/j.atmosenv.2011.01.043</a>, 2011.

Winderlich, J., Chen, H., Gerbig, C., Seifert, T., Kolle, O., Lavriš, J. V., Kaiser, C., Höfer, A., and Heimann, M.: Continuous low-maintenance CO2/CH4/H2O measurements at the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia, Atmos. Meas. Tech., 3, 1113–1128, <a href="http://dx.doi.org/10.5194/amt-3-1113-2010">https://doi.org/10.5194/amt-3-1113-2010</a>, 2010.

WMO: 15th WMO/IAEA Meeting of Exerts on Carbon Dioxide, Other Greenhouse Gases and Related Tracers Measurement Techniques, GAW Report, No. 194, 2011.

Yashiro, H., Sugawara, S., Sudo, K., Aoki, S., and Nakazawa, T.: Temporal and spatial variations of carbon monoxide over the western part of the Pacific Ocean, J. Geophys. Res., 114, D08305, <a href="http://dx.doi.org/10.1029/2008JD010876">https://doi.org/10.1029/2008JD010876</a>, 2009.

Zellweger, C., Hüglin, C., Klausen, J., Steinbacher, M., Vollmer, M., and Buchmann, B.: Inter-comparison of four different carbon monoxide measurement techniques and evaluation of the long-term carbon monoxide time series of Jungfraujoch, Atmos. Chem. Phys., 9, 3491–3503, <a href="http://dx.doi.org/10.5194/acp-9-3491-2009">https://doi.org/10.5194/acp-9-3491-2009</a>, 2009.

Zellweger, C., Steinbacher, M., and Buchmann, B.: Evaluation of new laser spectrometer techniques for in-situ carbon monoxide measurements, Atmos. Meas. Tech., 5, 2555–2567, <a href="http://dx.doi.org/10.5194/amt-5-2555-2012">https://doi.org/10.5194/amt-5-2555-2012</a>, 2012.

Zhao, C. L. and Tans, P. P.: Estimating uncertainty of the WMO mole fraction scale for carbon dioxide in air, J. Geophys. Res., 111, D08S09, <a href="http://dx.doi.org/10.1029/2005JD006003">https://doi.org/10.1029/2005JD006003</a>, 2006.