Preprints
https://doi.org/10.5194/amt-2021-303
https://doi.org/10.5194/amt-2021-303

  27 Oct 2021

27 Oct 2021

Review status: this preprint is currently under review for the journal AMT.

Mapping the spatial distribution of NO2 with in situ and remote sensing instruments during the Munich NO2 imaging campaign

Gerrit Kuhlmann1, Ka Lok Chan2,3,a, Sebastian Donner4, Ying Zhu2, Marc Schwaerzel1, Steffen Dörner4, Jia Chen5, Andreas Hueni6, Duc Hai Nguyen5,b, Alexander Damm6,7, Annette Schütt2, Florian Dietrich5, Dominik Brunner1, Cheng Liu8, Brigitte Buchmann1, Thomas Wagner3, and Mark Wenig2 Gerrit Kuhlmann et al.
  • 1Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf, Switzerland
  • 2Meteorological Institute, Ludwig-Maximillians-University (LMU), Munich, Germany
  • 3Remote Sensing Technology Institute (IMF), German Aerospace Center (DLR), Oberpfaffenhofen, Germany
  • 4Max Planck Institute for Chemistry (MPIC), Mainz, Germany
  • 5Environmental Sensing and Modeling, Technical University of Munich (TUM), Munich, Germany
  • 6Department of Geography, University of Zurich (UZH), Zurich, Switzerland
  • 7Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
  • 8Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China (USTC), Hefei, China
  • anow at: Rutherford Appleton Laboratory Space, Harwell Oxford, United Kingdom
  • bnow at: Leibniz Supercomputing Centre (LRZ), Garching bei München, Germany

Abstract. We present results from the Munich NO2 imaging campaign (MuNIC) where nitrogen dioxide (NO2) near-surface concentrations (NSC) and vertical column densities (VCD) were measured with stationary, mobile and airborne in situ and remote sensing instruments. The most intensive day of the campaign was 7 July 2016, when the NO2 VCD field was mapped with the Airborne Prism Experiment (APEX) imaging spectrometer. The spatial distribution of APEX VCDs was rather smooth with a horizontal gradient between lower values upwind and higher values downwind of the city center. The NO2 map had no pronounced source signatures except for the plumes of two combined heat and power plants (CHP). The APEX VCDs agree well with mobile MAX-DOAS observations from two vehicles conducted in the same afternoon (r = 0.55). In contrast to the VCDs, mobile NSC measurements revealed high spatial and temporal variability along the roads with highest values in congested areas and tunnels. The NOx emissions of the two CHP plants were estimated from the APEX observations using a mass-balance approach. The estimates are higher than reported emissions, but uncertainties are high because the campaign day was unstable and convective, resulting in low and highly variable wind speeds. The NOx emission estimates are consistent with CO2 emissions determined from two ground-based FTIR instruments operated near one CHP plant. We conclude that airborne imaging spectrometers are well suited to map the spatial distribution of NO2 VCDs over large areas. The emission plumes of point sources can be detected in the APEX observations, but accurate flow fields are essential to estimate emissions with sufficient accuracy. The application of airborne imaging spectrometers for studying NSCs, for example as input for epidemiological studies, is less straight forward and requires to account for the non-trivial relationship between VCDs and NSCs.

Gerrit Kuhlmann et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-303', Frederik Tack, 16 Nov 2021
  • RC2: 'Comment on amt-2021-303', Anonymous Referee #1, 21 Nov 2021

Gerrit Kuhlmann et al.

Gerrit Kuhlmann et al.

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Short summary
Nitrogen dioxide (NO2) is an air pollutant whose concentration often exceeds the air quality guideline values, especially in urban areas. To map the spatial distribution of NO2 in Munich, we conducted the Munich NO2 imaging campaign (MuNIC) where NO2 was measured with stationary, mobile and airborne in situ and remote sensing instruments. The campaign provides a unique dataset that has been used to compare the different instruments and to study the spatial variability of NO2 and its sources.