Articles | Volume 23, issue 20
Research article
 | Highlight paper
20 Oct 2023
Research article | Highlight paper |  | 20 Oct 2023

N2O as a regression proxy for dynamical variability in stratospheric trace gas trends

Kimberlee Dubé, Susann Tegtmeier, Adam Bourassa, Daniel Zawada, Douglas Degenstein, Patrick E. Sheese, Kaley A. Walker, and William Randel

Data sets

Level 2 Data ACE-FTS

Nitrous Oxide (N2O) – Combined Dataset NOAA/GML

Data Quality Flags for ACEFTS Level 2 Version 4.1/4.2 Data Set P. Sheese and K. Walker

OSIRIS Level 2 Data: Version 7.2 O3 D. Zawada, T. Warnock, A. Bourassa, and D. Degenstein

Model code and software

LOTUS Regression Code R. Damadeo, B. Hassler, D. Zawada, S. Frith, W. Ball, K. Chang, D. Degenstein, D. Hubert, S. Misois, I. Petropavlovskikh, C. Roth, V. Sofieva, W. Steinbrecht, K. Tourpali, C. Zerefos, J. Alsing, D. Balis, M. Coldewey-Egbers, K. Eleftheratos, S. Godin-Beekmann, A., Gruzdev, J. Kapsomenakis, A. Laeng, M. Laine, E. Maillard Barras, M. Taylor, T. von Clarmann, M. Weber, and J. Wild

Executive editor
Stratospheric ozone is important for the energy budget of the planetary atmosphere and for protecting life on Earth from harmful solar UV radiation. An unexpected decline in ozone in the extratropical lower stratosphere over the past two decades is therefore worrying and contrary to the Montreal Protocol's goal of ozone recovery. The study by Dube et al. adds important information to the ongoing discussion of this trend, which is being investigated internationally in activities such as SPARC/LOTUS, SPARC/OCTAVE-UTLS or the WMO ozone assessments. By their approach to use N2O as a tracer of stratospheric transport, the authors are able to separate ozone decrease due to circulation changes from a decrease caused by other, not further detailed reasons. They find that the latitudinal and altitudinal region where the ozone decrease cannot be explained by circulation changes is restricted to altitudes below 30hPa in the Northern hemisphere. They suggest a possible cause for the remaining ozone loss, namely a change in the tropopause altitude, thus narrowing successfully the search for processes leading to the observed ozone loss.
Short summary
This paper presents a technique for understanding the causes of long-term changes in stratospheric composition. By using N2O as a proxy for stratospheric circulation in the model used to calculated trends, it is possible to separate the effects of dynamics and chemistry on observed trace gas trends. We find that observed HCl increases are due to changes in the stratospheric circulation, as are O3 decreases above 30 hPa in the Northern Hemisphere.
Final-revised paper