Preprints
https://doi.org/10.5194/amt-2017-257
https://doi.org/10.5194/amt-2017-257

  01 Sep 2017

01 Sep 2017

Review status: this preprint was under review for the journal AMT. A revision for further review has not been submitted.

Retrieval of tropospheric NO2 columns over Berlin from high-resolution airborne observations with the spectrolite breadboard instrument

Tim Vlemmix1, Xinrui (Jerry) Ge1,a, Bryan T. G. de Goeij2, Len F. van der Wal2, Gerard C. J. Otter2, Piet Stammes3, Ping Wang3, Alexis Merlaud4, Dirk Schüttemeyer5, Andreas C. Meier6, J. Pepijn Veefkind3,1, and Pieternel F. Levelt3,1 Tim Vlemmix et al.
  • 1Delft University of Technology (TU-Delft), Delft, the Netherlands
  • 2TNO, Delft, the Netherlands
  • 3Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands
  • 4Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 5European Space Agency, Noordwijk, the Netherlands
  • 6Institute of Environmental Physics, University of Bremen, Germany
  • acurrently at: Wageningen University and Research (WUR), Wageningen, the Netherlands

Abstract. This paper presents the retrieval method that was developed to derive tropospheric NO2 columns from UV/VIS spectral measurements obtained with the Spectrolite Breadboard Instrument during the AROMAPEX campaign in Berlin (April 2016). A typical DOAS retrieval approach is followed. For the calculation of air mass factors this study specifically focuses on the impact of the surface reflectance, which varies considerably from pixel to pixel over this urban region. Ground-based aerosol optical thickness measurements are used as prior information. It is shown that retrieved surface reflectance shows good agreement with those derived from Landsat 8 measurements performed on the same day. Furthermore we demonstrate that tropospheric NO2 columns retrieved for pairs of adjacent pixels are self-consistent in the sense that they do not show a substantial systematic dependence on surface reflectance, in contrast to differential slant column densities. Also some cases are identified to illustrate this on a pixel-by-pixel level. An error budget is provided to quantify the impact of various assumptions on the accuracy of the retrieval of surface reflectance and tropospheric NO2 columns. Both in the morning and afternoon flight a NO2 plume is observed stretching out over Berlin from West to East. Peak values between 15 × 1015 and 20 × 1015 molec/cm2 are detected, whereas – at much lower spatial resolution – OMI detects peak values between 9 × 1015 (first overpass) and 4 × 1015 molec/cm2 (second overpass).

Tim Vlemmix et al.

 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Tim Vlemmix et al.

Tim Vlemmix et al.

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Short summary
We present a first analysis of UV/VIS spectral measurements obtained with the Spectrolite Breadboard Instrument (developed by TNO, The Netherlands) during the AROMAPEX campaign held in Berlin in April 2016 (campaign supported by ESA and EUFAR). This new sensor was used to measure air pollution in the form of tropospheric NO2 columns. The study focuses specifically on the retrieval of surface reflectances, an important intermediate step towards the final product.