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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-882
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
02 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Detection of a climatological short break in the Polar Night Jet in early winter and its relation to cooling over Siberia
Yuta Ando1, Koji Yamazaki1,2, Yoshihiro Tachibana1, Masayo Ogi3, and Jinro Ukita4 1Weather and Climate Dynamics Division, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan
2Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
3Centre for Earth Observation Science, University of Manitoba, 530 Wallace Building, Winnipeg MB R3T 2N2, Canada
4Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, Niigata 950-2181, Japan
Abstract. 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 monotonically from October through late December. Remarkably, the climatological PNJ temporarily stops increasing during late November. We examined this short break in terms of the atmospheric dynamical balance and 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 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.

Citation: Ando, Y., Yamazaki, K., Tachibana, Y., Ogi, M., and Ukita, J.: Detection of a climatological short break in the Polar Night Jet in early winter and its relation to cooling over Siberia, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-882, in review, 2017.
Yuta Ando et al.
Yuta Ando et al.
Yuta Ando et al.

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We found the climatological strong stratospheric westerly circumpolar wind stops increasing temporarily during November, when the upward propagation of large-scale atmospheric waves from the troposphere increases. The propagation of atmospheric waves, which is the strongest over Siberia, is related to strengthening of the low pressure. Longitudinally asymmetric forcing by land–sea heating contrasts caused by their different heat capacities might cause the strengthening of the low pressure.
We found the climatological strong stratospheric westerly circumpolar wind stops increasing...
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