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Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV-visible spectrometers during CINDI-2

Karin Kreher 1 Michel van Roozendael 2 François Hendrick 2 Arnoud Apituley 3 Ermioni Dimitropoulou 2 Udo Frieß 4 Andreas Richter 5 Thomas Wagner 6 Johannes Lampel 4 Nader Abuhassan 7 Li Ang 8 Monica Anguas 9 Alkis Bais 10 Nuria Benavent 9 Tim Bösch 5 Kristof Bognar 11 Alexander Borovski 12 Ilya Bruchkouski 13 Alexander Cede 7 Ka Lok Chan 14, 15 Sebastian Donner 6 Theano Drosoglou 10 Caroline Fayt 2 Henning Finkenzeller 16, 17 David Garcia-Nieto 9 Clio Gielen 2 Laura Gómez-Martín 18 Nan Hao 19 Bas Henzing 20 Jay Herman 7 Christian Hermans 2 Syedul Hoque 21 Hitoshi Irie 21 Junli Jin 22 Paul Johnston 23 Junaid Khayyam Butt 24 Fahim Khokhar 24 Theodore Koenig 16, 17 Jonas Kuhn 25, 6 Vinod Kumar 26 Cheng Liu 15 Jianzhong Ma 22 Alexis Merlaud 2 Abhishek Mishra 27 Moritz Müller 28 Monica Navarro-Comas 18 Mareike Ostendorf 5 Andrea Pazmino 29 Enno Peters 5, 30 Gaia Pinardi 2 Manuel Pinharanda 29 Ankie Piters 3 Ulrich Platt 25 Oleg Postylyakov 12 Cristina Prados-Roman 18 Olga Puentedura 18 Richard Querel 23 Alfonso Saiz-Lopez 9 Anja Schönhardt 5 Stefan Schreier 31 André Seyler 5 Vinayak Sinha 26 Elena Spinei 7, 32 Kimberly Strong 11 Frederik Tack 2 Xin Tian 8 Martin Tiefengraber 28 Jan-Lukas Tirpitz 25 Jeroen van Gent 2 Rainer Volkamer 16, 17 Mihalis Vrekoussis 5, 33, 34 Shanshan Wang 35, 9, 36 Zhuoru Wang 37 Mark Wenig 14 Folkard Wittrock 5 Pinhua Xie 8 Jin Xu 8 Margarita Yela 18 Chengxin Zhang 15 Xiaoyi Zhao 11, 38
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97∘ N, 4.93∘ E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O4) and ozone (O3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the selected reference (which is obtained from the median of either all data sets or a subset), and the rms error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the consistency between all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques.
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Karin Kreher, Michel van Roozendael, François Hendrick, Arnoud Apituley, Ermioni Dimitropoulou, et al.. Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV-visible spectrometers during CINDI-2. Atmospheric Measurement Techniques, European Geosciences Union, 2020, 13 (5), pp.2169-2208. ⟨10.5194/amt-13-2169-2020⟩. ⟨insu-02566681⟩



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