Ground-based validation of the Copernicus Sentinel-5P TROPOMI NO<sub>2</sub> measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks

Verhoelst, Tijl; Compernolle, Steven; Pinardi, Gaia; Lambert, Jean-Christopher; Eskes, Henk J.; Eichmann, Kai-Uwe; Fjæraa, Ann Mari; Granville, José; Niemeijer, Sander; Cede, Alexander; Tiefengraber, Martin; Hendrick, François; Pazmiño, Andrea; Bais, Alkiviadis; Bazureau, Ariane; Boersma, K. Folkert; Bognar, Kristof; Dehn, Angelika; Donner, Sebastian; Elokhov, Aleksandr; Gebetsberger, Manuel; Goutail, Florence; Grutter de la Mora, Michel; Gruzdev, Aleksandr; Gratsea, Myrto; Hansen, Georg H.; Irie, Hitoshi; Jepsen, Nis; Kanaya, Yugo; Karagkiozidis, Dimitris; Kivi, Rigel; Kreher, Karin; Levelt, Pieternel F.; Liu, Cheng; Müller, Moritz; Navarro Comas, Monica; Piters, Ankie J. M.; Pommereau, Jean-Pierre; Portafaix, Thierry; Prados-Roman, Cristina; Puentedura, Olga; Querel, Richard; Remmers, Julia; Richter, Andreas; Rimmer, John; Rivera Cárdenas, Claudia; Saavedra de Miguel, Lidia; Sinyakov, Valery P.; Stremme, Wolfgang; Strong, Kimberly; Van Roozendael, Michel; Veefkind, J. Pepijn; Wagner, Thomas; Wittrock, Folkard; Yela González, Margarita; Zehner, Claus

doi:https://doi.org/10.5194/amt-14-481-2021

Articles | Volume 14, issue 1

https://doi.org/10.5194/amt-14-481-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

TROPOMI on Sentinel-5 Precursor: first year in operation (AMT/ACP...

https://doi.org/10.5194/amt-14-481-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 1

Research article

|

22 Jan 2021

Research article |

| 22 Jan 2021

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

Tijl Verhoelst, Steven Compernolle, Gaia Pinardi, Jean-Christopher Lambert, Henk J. Eskes, Kai-Uwe Eichmann, Ann Mari Fjæraa, José Granville, Sander Niemeijer, Alexander Cede, Martin Tiefengraber, François Hendrick, Andrea Pazmiño, Alkiviadis Bais, Ariane Bazureau, K. Folkert Boersma, Kristof Bognar, Angelika Dehn, Sebastian Donner, Aleksandr Elokhov, Manuel Gebetsberger, Florence Goutail, Michel Grutter de la Mora, Aleksandr Gruzdev, Myrto Gratsea, Georg H. Hansen, Hitoshi Irie, Nis Jepsen, Yugo Kanaya, Dimitris Karagkiozidis, Rigel Kivi, Karin Kreher, Pieternel F. Levelt, Cheng Liu, Moritz Müller, Monica Navarro Comas, Ankie J. M. Piters, Jean-Pierre Pommereau, Thierry Portafaix, Cristina Prados-Roman, Olga Puentedura, Richard Querel, Julia Remmers, Andreas Richter, John Rimmer, Claudia Rivera Cárdenas, Lidia Saavedra de Miguel, Valery P. Sinyakov, Wolfgang Stremme, Kimberly Strong, Michel Van Roozendael, J. Pepijn Veefkind, Thomas Wagner, Folkard Wittrock, Margarita Yela González, and Claus Zehner

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Final revised paper (published on 22 Jan 2021)
Preprint (discussion started on 26 May 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review: Ground-based validation of the Copernicus Sentinel-5p TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks.', Anonymous Referee #1, 10 Jun 2020
- AC1: 'Author answers to RC1', Tijl Verhoelst, 19 Aug 2020
RC2: 'Minor revision recommended', Anonymous Referee #2, 07 Jul 2020
- AC2: 'Author answers to RC2', Tijl Verhoelst, 19 Aug 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Tijl Verhoelst on behalf of the Authors (19 Aug 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Aug 2020) by Jhoon Kim

RR by Anonymous Referee #2 (12 Sep 2020)

Suggestions for revision or reasons for rejection

The manuscript “Ground-based validation of the Copernicus Sentinel-5p TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks” presents the important information of the TROPOMI NO2 data accuracy and bias based on the comparison with ground based remote sensing measurement data. The enormous efforts are thought to be made for the accurate and fair evaluation of the satellite based NO2 retrievals, which inherently is different from those of the ground measurements with respect to the spatial, temporal and geometrical aspects. The manuscript deserves being published in AMT. However, there needs to be some minor additional analysis and revisions for better quality of the paper.

Cross sections:
Please compare the NO2 absorption cross sections used for the NO2 retrievals from MAX-DOAS, ZSL-DOAS, Pandora, and S5 using a table and summarize the differences in magnitude and its quantitative effects on the NO2 retrieval.

The errors of the ground data:
For the validation of the S5p, the uncertainties and errors of the NO2 products retrieved from the ground based MAX-DOAS, ZSL-DOAS, and Pandora should be addressed in detail and summarized in a table.

In Figure 7:
please make the dot size smaller, so that readers can distinguish their locations better.

Lines 175- 180:
The ZSL-DOAS measurements at sunset are adjusted to the early-afternoon S5p overpass time using a model-based correction factor. Thus, it is important for readers to understand the uncertainties of PPSCBOX 1D stacked-box photochemical model (Errera and Fonteyn, 2001; Hendrick et al., 2004)
Please address the uncertainty of its simulated diurnal cycle.

Validation methods:
The treatment of aerosol optical depth and its vertical profile is important foe the S5p NO2 quality.
To sophisticated validations for aerosol and cloud effects on discrepancy between the TROPOMI NO2 and those ground based data, consider additional comparisons of the S5p with those three ground based measurements in terms of AOD levels and cloud fraction. Check if the comparisons can be made in terms of aerosol peak eight as well.

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ED: Publish subject to minor revisions (review by editor) (25 Sep 2020) by Jhoon Kim

AR by Tijl Verhoelst on behalf of the Authors (12 Oct 2020) Author's response Manuscript

ED: Publish as is (05 Nov 2020) by Jhoon Kim

AR by Tijl Verhoelst on behalf of the Authors (15 Nov 2020)

Short summary

This paper reports on the ground-based validation of the NO₂ data produced operationally by the TROPOMI instrument on board the Sentinel-5 Precursor satellite. Tropospheric, stratospheric, and total NO₂ columns are compared to measurements collected from MAX-DOAS, ZSL-DOAS, and PGN/Pandora instruments respectively. The products are found to satisfy mission requirements in general, though negative mean differences are found at sites with high pollution levels. Potential causes are discussed.

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

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Peer-review completion

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