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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 Steven Compernolle 1 Gala Pinardi 1 Jean-Christopher Lambert 1 Henk J. Eskes 2 Kai-Uwe Eichmann 3 Ann Mari Fjæraa 4 José Granville 1 Sander Niemeijer 5 Alexander Cede 6, 7 Martin Tiefengraber 7 François Hendrick 1 Andrea Pazmino 8 Alkiviadis Bais 9 Ariane Bazureau 8 Klaas Folkert Boersma 2, 10 Kristof Bognar 11 Angelika Dehn 12 Sebastian Donner 13 Aleksandr Elokhov 14 Manuel Gebetsberger 7 Florence Goutail 8 Michel Grutter de la Mora 15 Aleksandr Gruzdev 14 Myrto Gratsea 16 Georg Hansen 4 Hitoshi Irie 17 Nis Jepsen 18 Yugo Kanaya 19 Dimitris Karagkiozidis 9 Rigel Kivi 20 Karin Kreher 21 Pieternel F. Levelt 2, 22 Cheng Liu 23 Moritz Müller 7 Monica Navarro-Comas 24 Ankie J. M. Piters 2 Jean-Pierre Pommereau 8 Thierry Portafaix 25 Olga Puentedura 24 Richard Querel 26 Julia Remmers 13 Andreas Richter 3 John Rimmer 27 Claudia Rivera Cárdenas 15 Lidia Saavedra de Miguel 12 Valery P. Sinyakov 28 Kimberley Strong 11 Michel van Roozendaël 1 Pepijn J. Veefkind 2 Thomas Wagner 11 Folkard Wittrock 29 Margarita Yela-González 21 Claus Zehner 10
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
10 Meteorology and Air Quality Group
WUR - Wageningen University and Research Centre [Wageningen]
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 : Wednesday, May 27, 2020 - 6:59:55 PM
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Tiji Verhoelst, Steven Compernolle, Gala Pinardi, Jean-Christopher Lambert, Henk J. Eskes, 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 Discussions, 2020, pp.(Under Review). ⟨10.5194/amt-2020-119⟩. ⟨insu-02635842⟩



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