Preprints
https://doi.org/10.5194/acp-2021-356
https://doi.org/10.5194/acp-2021-356

  28 May 2021

28 May 2021

Review status: a revised version of this preprint is currently under review for the journal ACP.

Comparison of Inorganic Chlorine in the Southern Hemispheric lowermost stratosphere during Late Winter 2019

Markus Jesswein1, Heiko Bozem2, Hans-Christoph Lachnitt2, Peter Hoor2, Thomas Wagenhäuser1, Timo Keber1, Tanja Schuck1, and Andreas Engel1 Markus Jesswein et al.
  • 1University of Frankfurt, Institute for Atmospheric and Environmental Sciences, Frankfurt, Germany
  • 2Johannes Gutenberg University of Mainz, Institute for Atmospheric Physics, Mainz, Germany

Abstract. Inorganic chlorine (Cly) is the sum of the degradation products of long-lived chlorinated source gases. These include the reservoir species (HCl and ClONO2) and active chlorine species (i.e. ClOx). The active chlorine species drive catalytic cycles that deplete ozone in the polar winter stratosphere. This work presents calculations of inorganic chlorine (Cly) derived from chlorinated source gas measurements on board the High Altitude and Long Range Research Aircraft (HALO) during the Southern hemisphere Transport, Dynamic and Chemistry (SouthTRAC) campaign in late winter and early spring 2019. Results are compared to Cly of the Northern Hemisphere derived from measurements of the POLSTRACC-GW-LCYCLE-SALSA (PGS) campaign in the Arctic winter of 2015/2016. A scaled correlation was used for PGS data, since not all source gases were measured. Cly from a scaled correlation was compared to directly determined Cly and agreed well. An air mass classification based on in situ N2O measurements allocates the measurements to the vortex, the vortex boundary region, and mid-latitudes. Although the Antarctic vortex was weakened in 2019 compared to previous years, Cly reached 1687 ± 20 ppt at 385 K, therefore up to around 50 % of total chlorine could be found in inorganic form inside the Antarctic vortex, whereas only 15 % of total chlorine could be found in inorganic form in the southern mid-latitudes. In contrast, only 40 % of total chlorine could be found in inorganic form in the Arctic vortex during PGS and roughly 20 % in the northern mid-latitudes. Differences inside the respective vortex reaches up to 565 ppt more Cly in the Antarctic vortex 2019 than in the Arctic vortex 2016 (at comparable distance to the local tropopause). As far as is known, this is the first comparison of inorganic chlorine within the respective polar vortex. Based on the results of these two campaigns, the difference of Cly inside the respective vortex is significant and larger than reported inter annual variations.

Markus Jesswein 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-2021-356', Anonymous Referee #1, 28 Jun 2021
  • RC2: 'Comment on acp-2021-356', Michelle Santee, 06 Jul 2021
  • AC1: 'Responses to referees', Markus Jesswein, 25 Aug 2021

Markus Jesswein et al.

Markus Jesswein et al.

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Short summary
This study presents and compares inorganic chlorine (Cly) derived from observations with the HALO research aircraft in the Antarctic late winter/early fall 2019 and the Arctic winter 2015–2016. Trend-corrected correlations from the Northern Hemisphere show excellent agreement with those from the Southern Hemisphere. After observation allocation inside and outside the vortex based on N2O measurements, results of the two campaigns reveal significant differences of Cly within the respective vortex.
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