AMT Atmospheric Measurement Techniques AMT Atmos. Meas. Tech. 1867-8548 Copernicus Publications Göttingen, Germany 10.5194/amt-5-457-2012 The Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI): design, execution, and early results Piters A. J. M. 1 Boersma K. F. 2 1 Kroon M. 1 Hains J. C. 3 Van Roozendael M. 4 Wittrock F. 5 Abuhassan N. 7 6 Adams C. 8 Akrami M. 8 Allaart M. A. F. 1 Apituley A. 10 1 Beirle S. 24 Bergwerff J. B. 10 Berkhout A. J. C. 10 Brunner D. 11 Cede A. 12 7 Chong J. 13 Clémer K. 4 Fayt C. 4 Frieß U. 14 Gast L. F. L. 10 Gil-Ojeda M. 9 Goutail F. 15 Graves R. 16 Griesfeller A. 15 Großmann K. 14 Hemerijckx G. 4 Hendrick F. 4 Henzing B. 17 Herman J. 7 12 Hermans C. 4 Hoexum M. 10 van der Hoff G. R. 10 Irie H. 18 Johnston P. V. 19 Kanaya Y. 18 Kim Y. J. 13 Klein Baltink H. 1 Kreher K. 19 de Leeuw G. 20 17 27 Leigh R. 16 Merlaud A. 4 Moerman M. M. 17 Monks P. S. 16 Mount G. H. 21 Navarro-Comas M. 9 Oetjen H. 22 Pazmino A. 15 Perez-Camacho M. 9 Peters E. 5 du Piesanie A. 1 Pinardi G. 4 Puentedura O. 9 Richter A. 5 Roscoe H. K. 23 Schönhardt A. 5 Schwarzenbach B. 11 Shaiganfar R. 24 Sluis W. 1 Spinei E. 21 Stolk A. P. 10 Strong K. 8 Swart D. P. J. 10 Takashima H. 18 Vlemmix T. 1 Vrekoussis M. 5 26 Wagner T. 24 Whyte C. 8 Wilson K. M. 10 1 Yela M. 9 Yilmaz S. 14 Zieger P. 25 Zhou Y. 11 Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands Technical University Eindhoven (TUE), Eindhoven, The Netherlands Maryland Department of the Environment (MDE), Baltimore, MD, USA Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium Institute of Environmental Physics (IUP), University of Bremen, Bremen, Germany Morgan State University (MSU), Baltimore, MD, USA NASA/Goddard Space Flight Center (GSFC), Greenbelt, MD, USA Department of Physics, University of Toronto, Toronto, Ontario, Canada National Institute for Aerospace technology (INTA), Madrid, Spain National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands Swiss Federal Laboratories for Materials Science and Technology (EMPA), Dübendorff, Switzerland University of Maryland, Baltimore County (UMBC), Catonsville, MD, USA Gwangju Institute of Science and Technology, Gwangiu, Republic of Korea Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Guyancourt, France Department of Chemistry, University of Leicester, Leicester, UK Netherlands Organization for Applied Scientific Research (TNO), Utrecht, The Netherlands Research Institute for Global Change, JAMSTEC, Yokohama, Japan National Institute of Water & Atmospheric Research (NIWA), Lauder, New Zealand Finnish Meteorological Institute (FMI), Helsinki, Finland Laboratory for Atmospheric Research, Washington State University (WSU), Pullman, WA, USA School of Chemistry, University of Leeds, Leeds, UK British Antarctic Survey (BAS), Cambridge, UK Max Planck Institute for Chemistry (MPIC), Mainz, Germany Laboratory of Atmospheric Chemistry, Paul Scherrer Institut (PSI), Villigen, Switzerland Research Center for Atmospheric Physics and Climatology, Academy of Athens, Athens, Greece Department of Physics, University of Helsinki, Helsinki, Finland 27 02 2012 5 2 457 485 Copyright: © 2012 A. J. M. Piters et al. 2012 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/ This article is available from https://amt.copernicus.org/articles/5/457/2012/amt-5-457-2012.html The full text article is available as a PDF file from https://amt.copernicus.org/articles/5/457/2012/amt-5-457-2012.pdf

From June to July 2009 more than thirty different in-situ and remote sensing instruments from all over the world participated in the Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI). The campaign took place at KNMI's Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands. Its main objectives were to determine the accuracy of state-of-the-art ground-based measurement techniques for the detection of atmospheric nitrogen dioxide (both in-situ and remote sensing), and to investigate their usability in satellite data validation. The expected outcomes are recommendations regarding the operation and calibration of such instruments, retrieval settings, and observation strategies for the use in ground-based networks for air quality monitoring and satellite data validation. Twenty-four optical spectrometers participated in the campaign, of which twenty-one had the capability to scan different elevation angles consecutively, the so-called Multi-axis DOAS systems, thereby collecting vertical profile information, in particular for nitrogen dioxide and aerosol. Various in-situ samplers and lidar instruments simultaneously characterized the variability of atmospheric trace gases and the physical properties of aerosol particles. A large data set of continuous measurements of these atmospheric constituents has been collected under various meteorological conditions and air pollution levels. Together with the permanent measurement capability at the CESAR site characterizing the meteorological state of the atmosphere, the CINDI campaign provided a comprehensive observational data set of atmospheric constituents in a highly polluted region of the world during summertime. First detailed comparisons performed with the CINDI data show that slant column measurements of NO<sub>2</sub>, O<sub>4</sub> and HCHO with MAX-DOAS agree within 5 to 15%, vertical profiles of NO<sub>2</sub> derived from several independent instruments agree within 25% of one another, and MAX-DOAS aerosol optical thickness agrees within 20–30% with AERONET data. For the in-situ NO<sub>2</sub> instrument using a molybdenum converter, a bias was found as large as 5 ppbv during day time, when compared to the other in-situ instruments using photolytic converters.

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