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© 2020. This work is published under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

The Tropospheric Monitoring Instrument (TROPOMI), aboard the Sentinel-5 Precursor (S5P) satellite, launched on 13 October 2017, provides measurements of atmospheric trace gases and of cloud and aerosol properties at an unprecedented spatial resolution of approximately 7×3.5 km2 (approx. 5.5×3.5 km2 as of 6 August 2019), achieving near-global coverage in 1 d. The retrieval of nitrogen dioxide (NO2) concentrations is a three-step procedure: slant column density (SCD) retrieval, separation of the SCD in its stratospheric and tropospheric components, and conversion of these into vertical column densities. This study focusses on the TROPOMI NO2 SCD retrieval: the retrieval method used, the stability of the SCDs and the SCD uncertainties, and a comparison with the Ozone Monitoring Instrument (OMI) NO2 SCDs.

The statistical uncertainty, based on the spatial variability of the SCDs over a remote Pacific Ocean sector, is 8.63 µmol m-2 for all pixels (9.45 µmol m-2 for clear-sky pixels), which is very stable over time and some 30 % less than the long-term average over OMI–QA4ECV data (since the pixel size reduction TROPOMI uncertainties are8 % larger). The SCD uncertainty reported by the differential optical absorption spectroscopy (DOAS) fit is about 10 % larger than the statistical uncertainty, while for OMI–QA4ECV the DOAS uncertainty is some 20 % larger than its statistical uncertainty. Comparison of the SCDs themselves over the Pacific Ocean, averaged over 1 month, shows that TROPOMI is about 5 % higher than OMI–QA4ECV, which seems to be due mainly to the use of the so-called intensity offset correction in OMI–QA4ECV but not in TROPOMI: turning that correction off means about 5 % higher SCDs. The row-to-row variation in the SCDs of TROPOMI, the “stripe amplitude”, is 2.15 µmol m-2, while for OMI–QA4ECV it is a factor of2 (5) larger in 2005 (2018); still, a so-called stripe correction of this non-physical across-track variation is useful for TROPOMI data. In short, TROPOMI shows a superior performance compared with OMI–QA4ECV and operates as anticipated from instrument specifications.

The TROPOMI data used in this study cover 30 April 2018 up to 31 January 2020.

Details

Title
S5P TROPOMI NO2 slant column retrieval: method, stability, uncertainties and comparisons with OMI
Author
Jos van Geffen 1   VIAFID ORCID Logo  ; K Folkert Boersma 2   VIAFID ORCID Logo  ; Eskes, Henk 1   VIAFID ORCID Logo  ; Sneep, Maarten 1 ; Mark ter Linden 3 ; Zara, Marina 2 ; Veefkind, J Pepijn 4 

 Satellite Observations Department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands 
 Satellite Observations Department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands; Meteorology and Air Quality Group, Wageningen University (WUR), Wageningen, the Netherlands 
 Satellite Observations Department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands; Science and Technology Corporation (S[&]T), Delft, the Netherlands 
 Satellite Observations Department, Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands; Faculty of Civil Engineering and Geosciences, Delft University of Technology (TUDelft), Delft, the Netherlands 
Pages
1315-1335
Publication year
2020
Publication date
2020
Publisher
Copernicus GmbH
ISSN
18671381
e-ISSN
18678548
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2414065676
Copyright
© 2020. This work is published under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.