EGU21-9668, updated on 04 Mar 2021
https://doi.org/10.5194/egusphere-egu21-9668
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

TROPOMI NO2 retrieval: December 2020 (v1.4) and April 2021 (v2.2) upgrades, and comparisons with OMI and ground-based remote sensing

Jos van Geffen1, Henk Eskes1, Maarten Sneep1, Gaia Pinardi2, Tijl Verhoelst2, Steven Compernolle2, Mark ter Linden1,3, Folkert Boersma1,4, and Pepijn Veefkind1,5
Jos van Geffen et al.
  • 1Royal Netherlands Meteorological Institute (KNMI), De Bilt, Netherlands
  • 2Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 3Science and Technology Corporation (S[&]T), Delft, The Netherlands
  • 4Wageningen University (WUR), Wageningen, The Netherlands
  • 5Delft University of Technology (TUDelft), Delft, The Netherlands

The Tropospheric Monitoring Instrument (TROPOMI) on the Sentinel-5 Precursor (S5P) satellite is a unique instrument, combining daily global coverage, very high signal-to-noise, a broad spectral range and very small pixels up to 3.5 x 5.5 km2. Retrievals are available for a large number of species, including NO2. Due to the very small pixels and daily revisit, TROPOMI provides detailed information on individual sources and source sectors like individual power plants, industrial complexes, cities and suburbs, highways, and even individual ships. The TROPOMI Level-2 NO2 product is available from 30 April 2018 onwards.

Validation exercises of TROPOMI v1.2 & v1.3 data (2018-2020) with OMI and ground-based remote sensing observations have shown that TROPOMI's tropospheric NO2 column are low by up to 50% over highly polluted areas compared to independent data. In contrast, the underlying slant columns of TROPOMI agree well with OMI and independent SAOZ observations. Differences between OMI and TROPOMI have been mainly attributed to the different cloud height retrieval, using the O2-O2 versus O2-A bands respectively.

In our presentation we discuss recent improvements in the TROPOMI NO2 retrieval and the impact these have on the tropospheric columns and on the comparisons with OMI and ground-based remote-sensing data.

Version v1.4, which became operational on 2 December 2020, entails a major improvement in the cloud height retrieval, based on a modification of the FRESCO-S cloud retrieval using the O2-A band observations. In particular the cloud height over scenes with a small cloud coverage have increased, resulting in larger tropospheric columns in the retrievals over polluted areas.

Version v2.2, to become operational in April/May 2021, includes similar cloud retrieval modifications. Furthermore, it provides a better treatment of saturation issues and transients, is using improved (ir)radiance measurements (level-1b v2 spectra) including degradation corrections, and includes a new albedo treatment.

The TROPOMI NO2 retrievals are compared with OMI retrievals (from the QA4ECV product) and to ground-based observations with MAXDOAS and PANDORA instruments.

How to cite: van Geffen, J., Eskes, H., Sneep, M., Pinardi, G., Verhoelst, T., Compernolle, S., ter Linden, M., Boersma, F., and Veefkind, P.: TROPOMI NO2 retrieval: December 2020 (v1.4) and April 2021 (v2.2) upgrades, and comparisons with OMI and ground-based remote sensing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9668, https://doi.org/10.5194/egusphere-egu21-9668, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.