Preprints
https://doi.org/10.5194/acp-2020-1215
https://doi.org/10.5194/acp-2020-1215

  15 Dec 2020

15 Dec 2020

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

Pollution trace gases C2H6, C2H2, HCOOH, and PAN in the North Atlantic UTLS: observations and simulations

Gerald Wetzel1, Felix Friedl-Vallon1, Norbert Glatthor1, Jens-Uwe Grooß2, Thomas Gulde1, Michael Höpfner1, Sören Johansson1, Farahnaz Khosrawi1, Oliver Kirner3, Anne Kleinert1, Erik Kretschmer1, Guido Maucher1, Hans Nordmeyer1, Hermann Oelhaf1, Johannes Orphal1, Christof Piesch1, Björn-Martin Sinnhuber1, Jörn Ungermann2, and Bärbel Vogel2 Gerald Wetzel et al.
  • 1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 2Research centre Jülich, Institute of Energy and Climate Research – Stratosphere (IEK-7), Jülich, Germany
  • 3Karlsruhe Institute of Technology, Steinbuch Centre for Computing, Karlsruhe, Germany

Abstract. Measurements of the pollution trace gases ethane (C2H6), ethyne (C2H2), formic acid (HCOOH), and peroxyacetyl nitrate (PAN) were performed in the North Atlantic upper troposphere and lowermost stratosphere (UTLS) region with the airborne limb imager GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) with high spatial resolution down to cloud top. Observations were made during flights with the German research aircraft HALO (High Altitude and LOng Range Research Aircraft) in the frame of the WISE (Wave-driven ISentropic Exchange) campaign, which was carried out in autumn 2017 from Shannon (Ireland) and Oberpfaffenhofen (Germany). Enhanced volume mixing ratios (VMR) of up to 2.2 ppbv C2H6, 0.2 ppbv C2H2, 0.9 ppbv HCOOH, and 0.4 ppbv PAN were detected during the flight on 13 September 2017 in the upper troposphere and around the tropopause above the British Isles. Since PAN has the longest lifetime of this foursome, elevated quantities of this molecule could be measured even in the lowermost stratosphere (locally up to 14 km). Backward trajectory calculations as well as global three-dimensional CLaMS simulations with artificial tracers of air mass origin have shown that the main sources of the observed pollutant species are forest fires in North America and anthropogenic pollution in South and Southeast Asia uplifted and moved within the Asian monsoon anticyclone (AMA) circulation system. After release from the AMA, these species or their precursor substances are transported by strong tropospheric winds over large distances, depending on their particular atmospheric lifetime of up to months. Observations are compared to simulations with the atmospheric models EMAC (ECHAM5/MESSy Atmospheric Chemistry) and CAMS (Copernicus Atmosphere Monitoring Service). These models are qualitatively able to reproduce the measured VMR enhancements but underestimate the absolute amount of the increase. Increasing the emissions in EMAC by a factor of 2 reduces the disagreement between simulated and measured results and illustrates the importance of the quality of emission databases used in chemical models.

Gerald Wetzel et al.

 
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Gerald Wetzel et al.

Gerald Wetzel et al.

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Short summary
Measurements of the pollutants C2H6, C2H2, HCOOH, and PAN were performed in the North Atlantic UTLS region with the airborne limb imager GLORIA in 2017. Enhanced amounts of these species were detected in the upper troposphere and even in the lowermost stratosphere (PAN). Main sources of these gases are forest fires in North America and anthropogenic pollution in South Asia. Simulations of EMAC and CAMS are qualitatively able to reproduce the measured data but underestimate the absolute amounts.
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