Detection of a climatological short break in the polar night jet in early winter and its relation to cooling over Siberia
<p>The polar night jet (PNJ) is a strong stratospheric westerly circumpolar wind at around 65° N in winter, and the strength of the climatological PNJ is widely recognized to increase from October through late December. Remarkably, the climatological PNJ temporarily stops increas...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/12639/2018/acp-18-12639-2018.pdf |
| Summary: | <p>The polar night jet (PNJ) is a strong stratospheric westerly circumpolar wind
at around 65° N in winter, and the strength of the climatological
PNJ is widely recognized to increase from October through late December.
Remarkably, the climatological PNJ temporarily stops increasing during late
November. We examined this <q>short break</q> in terms of the atmospheric dynamical
balance and the climatological seasonal march. We found that it results from
an increase in the upward propagation of climatological planetary waves from
the troposphere to the stratosphere in late November, which coincides with a
maximum of the climatological Eliassen–Palm (EP) flux convergence in the lower
stratosphere. The upward propagation of planetary waves at 100 hPa, which is
strongest over Siberia, is related to the climatological strengthening of the
tropospheric trough over Siberia. We suggest that longitudinally asymmetric
forcing by land–sea heating contrasts caused by their different heat
capacities can account for the strengthening of the trough.</p> |
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| ISSN: | 1680-7316 1680-7324 |