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)

1 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
2 KNMI - Royal Netherlands Meteorological Institute
3 NILU - Norsk Institutt for Luftforskning
4 Meteorology and Air Quality Group
5 TU Delft - Delft University of Technology
6 INTA - Instituto Nacional de Técnica Aeroespacial
7 Kyrgyz National University of Jusup Balasagyn
8 Department of Physics [Toronto]
9 BK Scientific GmbH
10 IUP - Institut für Umweltphysik [Bremen]
11 S [&] T - Science [&] Technology Corporation [Delft]
12 GSFC - NASA Goddard Space Flight Center
13 Institute of Meteorology and Geophysics [Innsbruck]
14 STRATO - LATMOS
15 Laboratory of Atmospheric Physics [Thessaloniki]
16 ESRIN - European Space Research Institute
17 MPIC - Max-Planck-Institut für Chemie
18 IAP - A.M.Obukhov Institute of Atmospheric Physics
19 Centro de Ciencias de la Atmosfera [Mexico]
20 NOA - National Observatory of Athens
21 CEReS - Center for Environmental Remote Sensing [Chiba]
22 DMI - Danish Meteorological Institute
23 RIGC - Research Institute for Global Change
24 Space and Earth Observation Centre [Sodankylä]
25 Department of Precision Machinery and Precision Instrumentation [Hefei]
26 LACy - Laboratoire de l'Atmosphère et des Cyclones
27 NIWA - National Institute of Water and Atmospheric Research [Lauder]
28 University of Manchester [Manchester]
29 IUP - Institute of Environmental Physics [Bremen]

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.

Domains: Ocean, Atmosphere

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, 2021, 14 (1), pp.481-510. ⟨10.5194/amt-14-481-2021⟩. ⟨insu-02635842v2⟩