From the middle stratosphere to the surface, using nitrous oxide to constrain the stratosphere-troposphere exchange of ozone
Stratosphere-troposphere exchange (STE) is an important source of tropospheric ozone, affecting all of atmospheric chemistry, climate, and air quality. Observations and the theory of tracer correlations provide only coarse (±20 %) global-mean constraints. For fluxes resolved by latitude and month we...
| Main Authors: | , |
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| Format: | Text |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/acp-2021-635 https://acp.copernicus.org/preprints/acp-2021-635/ |
| Summary: | Stratosphere-troposphere exchange (STE) is an important source of tropospheric ozone, affecting all of atmospheric chemistry, climate, and air quality. Observations and the theory of tracer correlations provide only coarse (±20 %) global-mean constraints. For fluxes resolved by latitude and month we rely on global chemistry-transport models (CTMs), and unfortunately, these 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. In this work, we use modeled tracers (N 2 O, CFCl 3 ) 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 2 O on annual and quasi-biennial cycles can be matched by the models. The STE flux of N 2 O-depleted air in our CTM 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 2 O and O 3 in the lowermost stratosphere provide a seasonal, hemispheric scaling of the N 2 O flux to that of O 3 . For N 2 O and CFCl 3 , we model greater southern hemispheric STE fluxes, a result supported by some metrics, but counter to prevailing theory of wave-driven stratospheric circulation. The STE flux of O 3 , however, is predominantly northern hemispheric, but observational constraints show that this is only caused by the Antarctic ozone hole. Here we show that metrics founded on observations can better constrain the STE O 3 flux which will help guide future model assessments. |
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