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Building the COllaborative Carbon Column Observing Network (COCCON): long-term stability and ensemble performance of the EM27/SUN Fourier transform spectrometer

Frey, Matthias and Sha, Mahesh K. and Hase, Frank and Kiel, Matthäus and Blumenstock, Thomas and Harig, Roland and Surawicz, Gregor and Deutscher, Nicholas M. and Shiomi, Kei and Franklin, Jonathan E. and Bösch, Hartmut and Chen, Jia and Grutter, Michel and Ohyama, Hirofumi and Sun, Youwen and Butz, André and Tsidu, Gizaw Mengistu and Ene, Dragos and Wunch, Debra and Cao, Zhensong and Garcia, Omaira and Ramonet, Michel and Vogel, Felix and Orphal, Johannes (2019) Building the COllaborative Carbon Column Observing Network (COCCON): long-term stability and ensemble performance of the EM27/SUN Fourier transform spectrometer. Atmospheric Measurement Techniques, 12 (3). pp. 1513-1530. ISSN 1867-8548. doi:10.5194/amt-12-1513-2019.

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In a 3.5-year long study, the long-term performance of a mobile, solar absorption Bruker EM27/SUN spectrometer, used for greenhouse gas observations, is checked with respect to a co-located reference Bruker IFS 125HR spectrometer, which is part of the Total Carbon Column Observing Network (TCCON). We find that the EM27/SUN is stable on timescales of several years; the drift per year between the EM27/SUN and the official TCCON product is 0.02 ppmv for XCO_2 and 0.9 ppbv for XCH_4, which is within the 1σ precision of the comparison, 0.6 ppmv for XCO_2 and 4.3 ppbv for XCH_4. The bias between the two data sets is 3.9 ppmv for XCO_2 and 13.0 ppbv for XCH_4. In order to avoid sensitivity-dependent artifacts, the EM27/SUN is also compared to a truncated IFS 125HR data set derived from full-resolution TCCON interferograms. The drift is 0.02 ppmv for XCO_2 and 0.2 ppbv for XCH_4 per year, with 1σ precisions of 0.4 ppmv for XCO_2 and 1.4 ppbv for XCH_4, respectively. The bias between the two data sets is 0.6 ppmv for XCO_2 and 0.5 ppbv for XCH_4. With the presented long-term stability, the EM27/SUN qualifies as an useful supplement to the existing TCCON network in remote areas. To achieve consistent performance, such an extension requires careful testing of any spectrometers involved by application of common quality assurance measures. One major aim of the COllaborative Carbon Column Observing Network (COCCON) infrastructure is to provide these services to all EM27/SUN operators. In the framework of COCCON development, the performance of an ensemble of 30 EM27/SUN spectrometers was tested and found to be very uniform, enhanced by the centralized inspection performed at the Karlsruhe Institute of Technology prior to deployment. Taking into account measured instrumental line shape parameters for each spectrometer, the resulting average bias across the ensemble with respect to the reference EM27/SUN used in the long-term study in XCO_2 is 0.20 ppmv, while it is 0.8 ppbv for XCH_4. The average standard deviation of the ensemble is 0.13 ppmv for XCO_2 and 0.6 ppbv for XCH_4. In addition to the robust metric based on absolute differences, we calculate the standard deviation among the empirical calibration factors. The resulting 2σ uncertainty is 0.6 ppmv for XCO_2 and 2.2 ppbv for XCH_4. As indicated by the executed long-term study on one device presented here, the remaining empirical calibration factor deduced for each individual instrument can be assumed constant over time. Therefore the application of these empirical factors is expected to further improve the EM27/SUN network conformity beyond the scatter among the empirical calibration factors reported above.

Item Type:Article
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URLURL TypeDescription
https://tccondata.orgRelated ItemData
Frey, Matthias0000-0003-0664-6817
Kiel, Matthäus0000-0002-9784-962X
Deutscher, Nicholas M.0000-0002-2906-2577
Grutter, Michel0000-0001-9800-5878
Butz, André0000-0003-0593-1608
Ene, Dragos0000-0001-5266-0930
Wunch, Debra0000-0002-4924-0377
Vogel, Felix0000-0002-2548-3390
Additional Information:© 2019 Author(s). This work is distributed under the Creative Commons Attribution 4.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 30 Apr 2018 – Discussion started: 04 Jun 2018 – Revised: 05 Dec 2018 – Accepted: 22 Feb 2019 – Published: 11 Mar 2019. Data availability: TCCON Karlsruhe data (Hase et al., 2014) are available from the TCCON data archive, hosted by CaltechDATA: EM27/SUN data are available upon request to the authors. Author contributions: MF: performed measurements, data analysis, paper writing; MKS performed measurements and contributed to data analysis. FH performed measurements, data analysis, and paper writing. MK contributed to data analysis. TB performed measurements and contributed to calibration efforts. RH contributed to calibration efforts. GS contributed to calibration efforts. NMD contributed to calibration efforts. KS contributed to calibration efforts. JF contributed to calibration efforts. HB contributed to calibration efforts. JC contributed to calibration efforts. MG contributed to calibration efforts. HO contributed to calibration efforts. YS contributed to calibration efforts. AB contributed to calibration efforts. GMT contributed to calibration efforts. DE contributed to calibration efforts and provided evidence of XH2O bias. DW contributed to calibration efforts. ZC contributed to calibration efforts. OG contributed to calibration efforts. MR contributed to calibration efforts. FV contributed to calibration efforts. JO supported the advance of the project and contributed to calibration efforts. The authors declare that they have no conflict of interest. We acknowledge support by the ACROSS research infrastructure of the Helmholtz Association of German Research Centres (HGF). This work was supported by funding from the Helmholtz Association in the framework of MOSES (Modular Observation Solutions for Earth Systems). We thank the National Center for Environmental Prediction (NCEP) for providing atmospheric temperature profiles. We thank the NASA science team for providing MLS data from the Aura satellite. We thank the Jungfraujoch NDACC team for providing Jungfraujoch FTIR data. Isamu Morino and Akihiro Hori contributed by procuring the NIES instrument and performing additional instrumental line shape measurements in Tsukuba. We acknowledge funding from the Australian Space Research Program – Greenhouse Gas Monitoring Project, Australian Research Council project DE140100178, and the Centre for Atmospheric Chemistry (CAC) Research Cluster supported by the University of Wollongong Faculty of Science, Medicine and Health. We thank Minqiang Zhou (BIRA-IASB) for his contribution to the tool which was used to truncate the IFS 125HR interferograms. We acknowledge support from ESA project 4000118115/16/NL/FF/gp: Technical Assistance for a Romanian Atmospheric Mobile Observation System (RAMOS). The article processing charges for this open-access publication were covered by a Research Centre of the Helmholtz Association. Edited by: Ilse Aben. Reviewed by: two anonymous referees.
Funding AgencyGrant Number
Helmholtz AssociationUNSPECIFIED
Australian Space Research ProgramUNSPECIFIED
Australian Research CouncilDE140100178
University of WollongongUNSPECIFIED
European Space Agency (ESA)4000118115/16/NL/FF/gp
Issue or Number:3
Record Number:CaltechAUTHORS:20190321-133059907
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94026
Deposited By: Tony Diaz
Deposited On:21 Mar 2019 21:46
Last Modified:16 Nov 2021 17:02

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