N<sub>2</sub>O as a regression proxy for dynamical variability in stratospheric trace gas trends
<p>Trends in stratospheric trace gases like <span class="inline-formula">HCl</span>, <span class="inline-formula">N<sub>2</sub>O</span>, <span class="inline-formula">O<sub>3</sub></span>, and <span cla...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/13283/2023/acp-23-13283-2023.pdf |
| Summary: | <p>Trends in stratospheric trace gases like <span class="inline-formula">HCl</span>, <span class="inline-formula">N<sub>2</sub>O</span>, <span class="inline-formula">O<sub>3</sub></span>, and <span class="inline-formula">NO<sub><i>y</i></sub></span> show a hemispheric asymmetry over the last 2 decades, with trends having opposing signs in the Northern Hemisphere and Southern Hemisphere. Here we use <span class="inline-formula">N<sub>2</sub>O</span>, a long-lived tracer with a tropospheric source, as a proxy for stratospheric circulation in the multiple linear regression model used to calculate stratospheric trace gas trends. This is done in an effort to isolate trends due to circulation changes from trends due to the chemical effects of ozone-depleting substances. Measurements from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) and the Optical Spectrograph and InfraRed Imager System (OSIRIS) are considered, along with model results from the Whole Atmosphere Community Climate Model (WACCM). Trends in <span class="inline-formula">HCl</span>, <span class="inline-formula">O<sub>3</sub></span>, and <span class="inline-formula">NO<sub><i>y</i></sub></span> for 2004–2018 are examined. Using the <span class="inline-formula">N<sub>2</sub>O</span> regression proxy, we show that observed <span class="inline-formula">HCl</span> increases in the Northern Hemisphere are due to changes in the stratospheric circulation. We also show that negative <span class="inline-formula">O<sub>3</sub></span> trends above 30 hPa in the Northern Hemisphere can be explained by a change in the circulation but that negative ozone trends at lower levels cannot. Trends in stratospheric <span class="inline-formula">NO<sub><i>y</i></sub></span> are found to be largely consistent with trends in <span class="inline-formula">N<sub>2</sub>O</span>.</p> |
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| ISSN: | 1680-7316 1680-7324 |