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Abstract In response to rising , chemistry‐climate models (CCMs) project that extratropical stratospheric ozone will increase, except around 10 and 17 km. We call the muted increases or reductions at these altitudes the “double dip.” The double dip results from surface warming (not stratospheric cooling). Using an idealized photochemical‐transport model, surface warming is found to produce the double dip via tropospheric expansion, which converts ozone‐rich stratospheric air into ozone‐poor tropospheric air. The lower dip results from expansion of the extratropical troposphere, as previously understood. The upper dip results from expansion of the tropical troposphere, low‐ozone anomalies from which are then transported into the extratropics. Large seasonality in the double dip in CCMs can be explained, at least in part, by seasonality in the stratospheric overturning circulation. The remote effects of the tropical tropopause on extratropical ozone complicate the use of (local) tropopause‐following coordinates to remove the effects of global warming.
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The Evolutions and Large‐Scale Mechanisms of Summer Stratospheric Ozone Intrusion Across Global Hotspots
Abstract Stratospheric ozone intrusions can have a significant impact on regional near‐surface ozone levels. Especially in summer, intrusions can contribute to extreme ozone events because of preexisting high ozone levels near the surface and cause serious health issues. Considering the increasing trend of surface ozone level, an understanding of stratospheric ozone intrusion is necessary. From a 19‐year Whole Atmosphere Community Climate Model, version 6 simulation and a stratospheric origin ozone tracer, we identify the global hotspots of stratospheric intrusions based on extreme tracer concentrations near the surface: North America, Africa, the Mediterranean, and the Middle East. We investigate the common underlying large‐scale mechanisms of the stratospheric intrusions over the identified hotspots from the lower stratosphere to the lower troposphere. From the trajectory analysis, we find that the upper‐level jet drives isentropic mixing near the jet axis and initiates stratospheric ozone intrusion. Subsequently, climatological descent at the lower troposphere brings the ozone down to the surface, which explains the spatial preference of summertime stratospheric intrusion events.
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- Award ID(s):
- 1802248
- PAR ID:
- 10503682
- Publisher / Repository:
- AGU
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 129
- Issue:
- 4
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2023JD039877
