S5P/TROPOMI NO2 slant column retrieval: stability & uncertainties
TROPOMI : Introduction OMI : Introduction

Introduction

An initial study into the stability and uncertainties of the S5P/TROPOMI NO₂ slant column density (SCD) retrieval was presented by van Geffen et al., 2020, which covers NO₂ retrieval data up to 31 Jan. 2020.

These pages provide an update of some of the graphs and data in that paper using NO2 data of version v2.4.0 and following, that is the collection 03 dataset: the full mission reprocessing with NO2-v2.4.0 with level-1b v2.1 as of 1 May 2018 and the subsequent offline processing as of 25 July 2022. Also discussed, where relevant, are differences w.r.t. older processing versions (collection 01 and 02 datasets. with older level-1b data) are mentioned, which are in most cases very small. See this page for an overview of the versions.

The results presented here are irregularly and manually updated and
currently cover the NO₂ SCD retrieval results up to:   30 April 2026

Note: a full mission reprocessing is planned to take place somewhere in 2026 or later with v2.9.0 or later -- if necessary, the analysis presented here will be re-done after that.

 

Contents

• Wavelength calibration of the (ir)radiance
• SCD error estimate & statistical uncertainty
• Stripe correction amplitude
• Vertical NO₂ column monitoring

Note that initially the TROPOMI NO₂ ground pixels had a size of approximately 7 by 3.5 km2 at nadir. On 6 Aug. 2019 the along-track size was reduced, leading to a ground pixels size of approximately 5.5 by 3.5 km2, which in turn leads to somewhat higher uncertainty estimates.

 

Data selection for the analysis

As in van Geffen et al., 2020, the analysis is based on orbits over the Pacific Ocean (i.e. away from anthropogenic sources of NO₂): for each day the first available orbit with satellite (nadir viewing) equator crossings west of about -135°. Such a Pacific Ocean orbit is missing on a few days and these days are therefore skipped.

Two latitude ranges are used, depending on the type of analysis:

• The "Tropical Latitude" (TL) range:
  all scanlines that have their sub-satellite latitude point -- corresponding approximately to the nadir viewing detector rows -- within a 30° range that moves along with the seasons, in an attempt to filter out seasonality in the NO₂ data (on 1 January the TL range covers [-30°:0°], while half a year later it covers [0°:+30°]); with this moving range, the solar zenith angle remains more or less the same throughout the year.
• The "Pacific Ocean" (PO) range:
  all groundpixels that have a central latitude within [-60°:+60°].

Slant and vertical NO₂ column values are given here in the SI unit mol/m2 (as in the TROPOMI data files) and in several places also in the more commenly unit molecules/cm2; the conversion factor between these two is 6.02214e19. For example, 10.0 μmol/m2 corresponds to 6.022+14 molecules/cm2, and 2.0e15 molecules/cm2 corresponds to 33.211 μmol/m2.

 

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References

• van Geffen, J.H.G.M., Eskes, H.J., Sneep, M., ter Linden, M. and Veefkind, J.P.: 2026,
  "Improved NO2 spectral fits for TROPOMI and OMI by removing wavelengths around 430 nm,"
  Atmos. Meas. Tech., in review.  ==>  On-line paper

• van Geffen, J.H.G.M., Eskes, H.J., Compernolle, S., Pinardi, G., Verhoelst, T., Lambert, J.-C., Sneep, M., ter Linden, M., Ludewig, A., Boersma, K.F. and Veefkind, J.P.: 2022,
  "Sentinel-5P TROPOMI NO₂ retrieval: impact of version v2.2 improvements and comparisons with OMI and ground-based data,"
  Atmos. Meas. Tech. 15, 2037-2060.  ==>  On-line paper  |  PDF file (13 MB)

• van Geffen, J.H.G.M., Boersma, K.F., Eskes, H.J., Sneep, M., ter Linden, M., Zara, M. and Veefkind, J.P.: 2020,
  "S5P/TROPOMI NO₂ slant column retrieval: method, stability, uncertainties and comparisons with OMI,"
  Atmos. Meas. Tech. 13, 1315-1335.  ==>  On-line paper  |  PDF file (8 MB)

• The standard operational TROPOMI NO₂ data product and its usage are described in the
  • Algorithm Theoretical Basis Document [ATBD]
  • Product User Manual [PUM]
  • Product ReadMe File [PRF]
  The latest version of these documents can be found at the Products and Algorithms page of ESA

• Zara, M., Boersma, K.F., De Smedt, I., Richter, A., Peters, E., Van Geffen, J.H.G.M., Beirle, S., Wagner, T., Van Roozendael, M., Marchenko, S., Lamsal, L. and Eskes, H.J., 2018:
  "Improved slant column density retrieval of nitrogen dioxide and formaldehyde for OMI and GOME-2A from QA4ECV: intercomparison, uncertainty characterization, and trends,"
  Atmos. Meas. Tech. 11, 4033-4058.  ==>  On-line paper  |  PDF file (11 MB)

last modified: 26 June 2026
Contact: Jos van Geffen   < geffen [at] knmi [dot] nl >
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