25 Apr 2022
25 Apr 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Enhanced sulfur in the UTLS in spring 2020

Laura Tomsche1,2, Andreas Marsing1,2, Tina Jurkat-Witschas1, Johannes Lucke1,5, Stefan Kaufmann1, Katharina Kaiser3, Johannes Schneider3, Monika Scheibe1, Hans Schlager1, Lenard Röder3, Horst Fischer3, Florian Obersteiner4, Andreas Zahn4, Jos Lelieveld3, and Christiane Voigt1,2 Laura Tomsche et al.
  • 1German Aerospace Center, 82234 Weßling, Germany
  • 2Johannes Gutenberg University Mainz, 55099 Mainz, Germany
  • 3Max Planck Institute for Chemistry, 55128 Mainz, Germany
  • 4Karlsruhe Institute for Technology (KIT), 76021 Karlsruhe, Germany
  • 5Faculty of Aerospace Engineering, Delft University of Technology, 2629 Delft, Netherlands

Abstract. Sulfur compounds in the upper troposphere and lower stratosphere (UTLS) impact the atmosphere radiation budget, either directly as particles or indirectly as precursor gas for new particle formation. In situ measurements in the UTLS are rare, but are important to better understand the impact of the sulfur budget on climate. The BLUESKY mission in May/June 2020 explored an unprecedented situation. 1) The UTLS experienced extraordinary dry conditions in spring 2020 over Europe, in comparison to previous years and 2) the first lockdown of the COVID-19 pandemic caused major emission reductions from industry, ground, and airborne transportation. With the two research aircraft HALO and Falcon, 20 flights were conducted over Central Europe and the North Atlantic to investigate the atmospheric composition with respect to trace gases, aerosol, and clouds. Here, we focus on measurements of sulfur dioxide (SO2) and particulate sulfate (SO42-) in the altitude range of 8 to 14.5 km which show unexpectedly enhanced mixing ratios of SO2 in the upper troposphere and of SO42- in the lowermost stratosphere. In the UT, we find SO2 mixing ratios of (0.07 ± 0.01) ppb, caused by the remaining air traffic, reduced SO2 sinks due to low OH and low cloud fractions, and to a minor extend by uplift from boundary layer sources. Particulate sulfate showed elevated mixing ratios of up to 0.33 ppb in the LS. We suggest that the eruption of the volcano Raikoke in June 2019, which emitted about 1 Tg SO2 into the stratosphere in northern midlatitudes caused these enhancements, in addition to Siberian and Canadian wildfires and other minor volcanic eruptions. Our measurements can help to test models and lead to new insights in the distribution of sulfur compounds in the UTLS, their sources and sinks. Moreover, these results can contribute to improve simulations of the radiation budget in the UTLS with respect to sulfur effects.

Laura Tomsche 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 acp-2022-274', Anonymous Referee #1, 27 May 2022
  • RC2: 'Comment on acp-2022-274', Daniele Visioni, 04 Jul 2022
    • AC1: 'Reply on RC2', Laura Tomsche, 09 Aug 2022

Laura Tomsche et al.

Laura Tomsche et al.


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Short summary
The detection of sulfur compounds in the upper troposphere (UT) and lower stratosphere (LS) is a challenge. In-flight measurements of SO2 and sulfate aerosol were performed during the BLUESKY mission in spring 2020 under exceptional atmospheric conditions. Reduced sinks in the dry UTLS and lower but still significant air traffic influenced the enhanced SO2 in the UT and aged volcanic plumes enhanced the LS sulfate aerosol both impacting the atmospheric radiation budget and global climate.