From the middle stratosphere to the surface, using nitrous oxide to constrain the stratosphere–troposphere exchange of ozone
<p>Stratosphere–troposphere exchange (STE) is an important source of tropospheric ozone, affecting all of atmospheric chemistry, climate, and air quality. The study of impacts needs STE fluxes to be resolved by latitude and month, and for this, we rely on global chemistry models, whose results...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/2079/2022/acp-22-2079-2022.pdf |
| Summary: | <p>Stratosphere–troposphere exchange (STE) is an important source of
tropospheric ozone, affecting all of atmospheric chemistry, climate, and air quality. The study of impacts needs STE fluxes to be resolved by latitude and month, and for this, we rely on global chemistry models, whose results diverge greatly. Overall, we lack guidance from model–measurement metrics that inform us about processes and patterns related to the STE flux of ozone (O<span class="inline-formula"><sub>3</sub></span>). In this work, we use modeled tracers (N<span class="inline-formula"><sub>2</sub></span>O and CFCl<span class="inline-formula"><sub>3</sub></span>), whose distributions and budgets can be constrained by satellite and surface
observations, allowing us to follow stratospheric signals across the
tropopause. The satellite-derived photochemical loss of N<span class="inline-formula"><sub>2</sub></span>O on annual
and quasi-biennial cycles can be matched by the models. The STE flux of
N<span class="inline-formula"><sub>2</sub></span>O-depleted air in our chemistry transport model drives surface
variability that closely matches observed fluctuations on both annual and
quasi-biennial cycles, confirming the modeled flux. The observed tracer
correlations between N<span class="inline-formula"><sub>2</sub></span>O and O<span class="inline-formula"><sub>3</sub></span> in the lowermost stratosphere
provide a hemispheric scaling of the N<span class="inline-formula"><sub>2</sub></span>O STE flux to that of
O<span class="inline-formula"><sub>3</sub></span>. For N<span class="inline-formula"><sub>2</sub></span>O and CFCl<span class="inline-formula"><sub>3</sub></span>, we model greater southern hemispheric
STE fluxes, a result supported by some metrics, but counter to the prevailing theory of wave-driven stratospheric circulation. The STE flux of O<span class="inline-formula"><sub>3</sub></span>, however, is predominantly northern hemispheric, but evidence shows that this is caused by the Antarctic ozone hole reducing southern hemispheric O<span class="inline-formula"><sub>3</sub></span> STE by 14 %. Our best estimate of the current STE O<span class="inline-formula"><sub>3</sub></span> flux based on a range of constraints is 400 Tg(O<span class="inline-formula"><sub>3</sub></span>) yr<span class="inline-formula"><sup>−1</sup></span>, with a <span class="inline-formula">1<i>σ</i></span> uncertainty of <span class="inline-formula">±</span>15 % and with a NH : SH ratio ranging from <span class="inline-formula">50:50</span> to <span class="inline-formula">60:40</span>. We identify a range of observational metrics that can better constrain the modeled STE O<span class="inline-formula"><sub>3</sub></span> flux in future assessments.</p> |
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| ISSN: | 1680-7316 1680-7324 |