The spring transition of the North Pacific jet and its relation to deep stratosphere-to-troposphere mass transport over western North America
<p>Stratosphere-to-troposphere mass transport to the planetary boundary layer (STT-PBL) peaks over the western United States during boreal spring, when deep stratospheric intrusions are most frequent. The tropopause-level jet structure modulates the frequency and character of intrusions, altho...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/2781/2021/acp-21-2781-2021.pdf |
| Summary: | <p>Stratosphere-to-troposphere mass transport to the planetary
boundary layer (STT-PBL) peaks over the western United States during boreal
spring, when deep stratospheric intrusions are most frequent. The
tropopause-level jet structure modulates the frequency and character of
intrusions, although the precise relationship between STT-PBL and jet
variability has not been extensively investigated. In this study, we
demonstrate how the North Pacific jet transition from winter to summer leads
to the observed peak in STT-PBL. We show that the transition enhances
STT-PBL through an increase in storm track activity which produces
highly amplified Rossby waves and more frequent deep stratospheric
intrusions over western North America. This dynamic transition coincides
with the gradually deepening PBL, further facilitating STT-PBL in spring. We
find that La Niña conditions in late winter are associated with an
earlier jet transition and enhanced STT-PBL due to deeper and more frequent
tropopause folds. An opposite response is found during El Niño
conditions. El Niño–Southern
Oscillation (ENSO) conditions also influence STT-PBL in late spring or early
summer, during which time La Niña conditions are associated with larger
and more frequent tropopause folds than both El Niño and ENSO-neutral
conditions. These results suggest that knowledge of ENSO state and the North Pacific jet structure in late winter could be leveraged for predicting the
strength of STT-PBL in the following months.</p> |
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| ISSN: | 1680-7316 1680-7324 |