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Ground-based validation of the Copernicus Sentinel-5p TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks

Tiji Verhoelst 1, * Gala Pinardi 1 Henk J. Eskes 2 Ann Mari Fjæraa 3 Klaas Folkert Boersma 2, 4 Pieternel F. Levelt 2, 5 Monica Navarro-Comas 6 Ankie J. M. Piters 2 Valery P. Sinyakov 7 Kimberley Strong 8 Pepijn J. Veefkind 2 Margarita Yela-González 9 Tijl Verhoelst Steven Compernolle 1 Gaia Pinardi Jean-Christopher Lambert 1 Henk J Eskes Kai-Uwe Eichmann 10 Ann Mari Fjaeraa José Granville 1 Sander Niemeijer 11 Alexander Cede 12, 13 Martin Tiefengraber 13 François Hendrick 1 Andrea Pazmino 14 Alkiviadis Bais 15 Ariane Bazureau 14 K Folkert Boersma Kristof Bognar 8 Angelika Dehn 16 Sebastian Donner 17 Aleksandr Elokhov 18 Manuel Gebetsberger 13 Florence Goutail 14 Michel Grutter de La Mora 19 Aleksandr Gruzdev 18 Myrto Gratsea 20 Georg H Hansen 3 Hitoshi Irie 21 Nis Jepsen 22 Yugo Kanaya 23 Dimitris Karagkiozidis 15 Rigel Kivi 24 Karin Kreher 9 Pieternel F Levelt Cheng Liu 25 Moritz Müller 13 Monica Navarro Comas Ankie J M Piters Jean-Pierre Pommereau 14 Thierry Portafaix 26 Cristina Prados-Roman 6 Olga Puentedura 6 Richard Querel 27 Julia Remmers 17 Andreas Richter 10 John Rimmer 28 Claudia Rivera Cárdenas 19 Lidia Saavedra de Miguel 16 Valery P Sinyakov Wolfgang Stremme 19 Kimberly Strong Michel van Roozendaël 1 J Pepijn Veefkind Thomas Wagner 8 Folkard Wittrock 29 Margarita Yela González Claus Zehner 4 
* Corresponding author
4 Meteorology and Air Quality Group
WUR - Wageningen University and Research [Wageningen]
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : This paper reports on consolidated ground-based validation results of the atmospheric NO2 data produced operationally since April 2018 by the TROPOMI instrument on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5p) satellite. Tropospheric, stratospheric, and total NO2 column data from S5p are compared to correlative measurements collected from, respectively, 19 Multi-Axis DOAS (MAX-DOAS), 26 NDACC Zenith-Scattered-Light DOAS (ZSL-DOAS), and 25 PGN/Pandora instruments distributed globally. The validation methodology gives special care to minimizing mismatch errors due to imperfect spatio-temporal co-location of the satellite and correlative data, e.g., by using tailored observation operators to account for differences in smoothing and in sampling of atmospheric structures and variability, and photochemical modelling to reduce diurnal cycle effects. Compared to the ground-based measurements, S5p data show, on an average: (i) a negative bias for the tropospheric column data, of typically −23 to −37 % in clean to slightly polluted conditions, but reaching values as high as −51 % over highly polluted areas; (ii) a slight negative bias for the stratospheric column data, of about −0.2 Pmolec/cm2, i.e. approx. −2 % in summer to −15 % in winter; and (iii) a bias ranging from zero to −50 % for the total column data, found to depend on the amplitude of the total NO2 column, with small to slightly positive bias values for columns below 6 Pmolec/cm2 and negative values above. The dispersion between S5p and correlative measurements contains mostly random components, which remain within mission requirements for the stratospheric column data (0.5 Pmolec/cm2), but exceed those for the tropospheric column data (0.7 Pmolec/cm2). While a part of the biases and dispersion may be due to representativeness differences, it is known that errors in the S5p tropospheric columns exist due to shortcomings in the (horizontally coarse) a-priori profile representation in the TM5-MP chemistry transport model used in the S5p retrieval, and to a lesser extent, to the treatment of cloud effects. Although considerable differences (up to 2 Pmolec/cm2 and more) are observed at single ground-pixel level, the near-real-time (NRTI) and off-line (OFFL) versions of the S5p NO2 operational data processor provide similar NO2 column values and validation results when globally averaged, with the NRTI values being on average 0.79 % larger than the OFFL values.
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Submitted on : Friday, January 22, 2021 - 4:56:48 PM
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Tiji Verhoelst, Gala Pinardi, Henk J. Eskes, Ann Mari Fjæraa, Klaas Folkert Boersma, et al.. Ground-based validation of the Copernicus Sentinel-5p TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks. Atmospheric Measurement Techniques, European Geosciences Union, 2021, 14 (1), pp.481-510. ⟨10.5194/amt-14-481-2021⟩. ⟨insu-02635842v2⟩



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