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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Mar 2019

Research article | 12 Mar 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Impact of synthetic spaceborne NO2 observations from the Sentinel-4 and Sentinel-5p platforms on tropospheric NO2 analyses

Renske Timmermans1, Arjo Segers1, Lyana Curier2, Rachid Abida3, Jean-Luc Attié3,4, Laaziz El Amraoui3, Henk Eskes5, Johan de Haan5, Jukka Kujanpää6, William Lahoz7, Albert Oude Nijhuis8, Samuel Quesada3, Philippe Ricaud3, Pepijn Veefkind5, and Martijn Schaap1,9 Renske Timmermans et al.
  • 1TNO, Netherlands Organisation for Applied Research, Climate, Air and sustainability division, 3508 TA Utrecht, The Netherlands
  • 2TNO, now at CBS, Central Bureau of Statistics, Heerlen, The Netherlands
  • 3CNRM-GAME, Météo-France/CNRS UMR 3589, Toulouse, France
  • 4Université de Toulouse, Laboratoire d'Aérologie, CNRS UMR 5560, Toulouse, France
  • 5Royal Netherlands Meteorological Institute (KNMI), P.O. Box 201, 3730 AE De Bilt, the Netherlands
  • 6Finnish Meteorological Institute (FMI), P.O. Box 503, 00101 Helsinki, Finland
  • 7NILU – Norwegian Institute for Air Research, P.O. Box 100, 2027 Kjeller, Norway
  • 8KNMI, now at SkyEcho, Rotterdam, the Netherlands
  • 9FUB – Free University Berlin, Institut für Meteorologie, Carl-Heinrich-Becker-Weg 6–10, 12165 Berlin, Germany

Abstract. We present an Observing System Simulation Experiment (OSSE) dedicated to the evaluation of the added value of the Sentinel 4 and Sentinel 5P missions for tropospheric nitrogen dioxide (NO2). Sentinel 4 is a geostationary (GEO) mission covering the European continent, providing observations with high temporal resolution (hourly). Sentinel 5P is a low-Earth Orbiting (LEO) mission providing daily observations but with a global coverage. The OSSE experiment has been carefully designed, with separate models for the simulation of observations and for the assimilation experiments, and with conservative estimates of the total observation uncertainties. In the experiment we simulate Sentinel 4 and Sentinel 5P tropospheric NO2 columns and surface ozone concentrations at 7 by 7 km resolution over Europe for two three-month summer and winter periods. The synthetic observations are based on a nature run (NR) from a chemistry transport model (MOCAGE) and error estimates using instrument characteristics. We assimilate the simulated observations into a chemistry transport model (LOTOS-EUROS) independent from the NR to evaluate their impact on modelled NO2 tropospheric columns and surface concentrations. The results are compared to an operational system where only ground-based ozone observations are ingested. Both instruments have an added value on analysed NO2 columns and surface values, reflected in decreased biases, and improved correlations. The Sentinel 4 NO2 observations with hourly temporal resolution benefit modelled NO2 analyses throughout the entire day where the daily Sentinel 5P NO2 observations have a slightly lower impact that lasts up to 3–6 hours after overpass. The evaluated benefits may be even higher in reality as the applied error estimates were shown to be higher than actual errors in the now operational Sentinel 5P NO2 products. We show that an accurate representation of the NO2 profile is crucial for the benefit of the column observations on surface values. The results support the need for having a combination of GEO and LEO missions for NO2 analyses in view of the complementary benefits of hourly temporal resolution (GEO, Sentinel 4) and global coverage (LEO, Sentinel 5P).

Renske Timmermans et al.
Interactive discussion
Status: open (extended)
Status: open (extended)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Renske Timmermans et al.
Renske Timmermans et al.
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Publications Copernicus
Short summary
We present an evaluation of the added value of the Sentinel 4 and Sentinel 5P missions for air quality analyses of NO2. For this, synthetic observations for both missions are generated and combined with a chemistry transport model. While hourly Sentinel 4 NO2 observations over Europe benefit modelled NO2 analyses throughout the entire day, daily Sentinel 5P NO2 observations with global coverage show an impact up to 3–6 hours after overpass. This supports the need for a combination of missions.
We present an evaluation of the added value of the Sentinel 4 and Sentinel 5P missions for air...