07 Apr 2022
07 Apr 2022
Status: this preprint is currently under review for the journal ACP.

Stratospheric ozone trends for 1984–2021 in the SAGE II – OSIRIS – SAGE III/ISS composite dataset

Kristof Bognar1, Susann Tegtmeier1, Adam Bourassa1, Chris Roth1,a, Taran Warnock1, Daniel Zawada1, and Doug Degenstein1 Kristof Bognar et al.
  • 1Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, SK, Canada
  • anow at: Vehicle Prognostics Research Group, Hamilton, ON, Canada

Abstract. After decades of depletion in the 20th century, near-global ozone now shows clear signs of recovery in the upper stratosphere. The ozone column, however, remained largely constant since the turn of the century, mainly due to changes in the lower stratosphere. In the tropical lower stratosphere, ozone is expected to decrease as a consequence of enhanced upwelling driven by increasing greenhouse gas concentrations, and this is consistent with observations. There is recent evidence, however, that mid-latitude ozone continues to decrease as well, contrary to model predictions. These changes are likely related to dynamical variability, but the impact of changing circulation patterns on stratospheric ozone is not well understood. Here we use merged measurements from the Stratospheric Aerosol and Gas Experiment II (SAGE II), the Optical Spectrograph and InfraRed Imaging System (OSIRIS), and SAGE III/ISS to quantify ozone changes in the 2000–2021 period. We implement a sampling correction for the OSIRIS and SAGE III/ISS datasets, and assess trend significance taking into account temporal differences with respect to Aura Microwave Limb Sounder data. We show that ozone increased by 2–6 % in the upper and 1–3 % in the middle stratosphere since 2000, while lower stratospheric ozone decreased by similar amounts. These decreases are significant in the tropics (>95 % confidence), but not necessarily at mid-latitudes (> 80 % confidence). In the upper and middle stratosphere, changes since 2010 point to hemispheric asymmetries in ozone recovery. Significant positive trends are present in the southern hemisphere, while ozone at northern mid-latitudes has remained largely unchanged in the last decade. These differences might be related to asymmetries and long-term variability in the Brewer-Dobson circulation. Circulation changes impact ozone in the lower stratosphere as well. In tropopause relative coordinates, most of the negative trends in the tropics lose significance, highlighting the impacts of a warming tropopause and increasing tropopause altitudes.

Kristof Bognar et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'A solid and well written paper. Congratulations.', Anonymous Referee #1, 07 May 2022
  • RC2: 'Comment on acp-2022-252', Robert Damadeo, 16 May 2022

Kristof Bognar et al.

Kristof Bognar et al.


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Short summary
We quantify recent changes in stratospheric ozone (outside the polar regions) using a combination of three satellite datasets. We find that upper stratospheric ozone increased significantly since 2000, although the recovery shows an unexpected pause in the northern hemisphere. Combined with the likely decrease of ozone in the lower stratosphere, this presents an interesting challenge for predicting the future of the ozone layer.