Journal
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Volume 124, Issue 23, Pages 12568-12586Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019JD030966
Keywords
Quasi-biennial oscillation; Polar vortex; Stratosphere
Categories
Funding
- National Key Research and Development Program of China [2018YFC1506003]
- National Natural Science Foundation of China [41630421, 41705022]
- College of Atmospheric Sciences, Lanzhou University
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Using potential vorticity to define Northern Hemisphere (NH) stratospheric polar vortex strength and position, the influence of the QBO on the polar vortex in winter is analyzed. The results show that the weakened/enhanced NH polar vortex in the lower stratosphere during easterly/westerly QBO (E/WQBO) phases is more noticeable in January and February than in November and December. Furthermore, the NH polar vortex shows a shift toward the Eurasian continent and away from North America in winter during EQBO phases compared with that during WQBO phases, with a greater shift in January and February than in November and December. The weaker QBO impact on the zonal mean zonal wind and temperature in February found in previous studies may be related to the cancelling effects of opposite-signed anomalies over Eurasia and North America induced by the polar vortex shift associated with the QBO. During EQBO phases the upper stratospheric easterly anomalies in early winter increase the frequency of negative refractive index in the middle and high latitudes in late winter. Less planetary wave 1 propagates upward into the upper stratosphere and more wave 1 accumulates in the lower stratosphere, leading to the weakening and shift of the polar vortex in late winter. In addition, the poleward displacement of the subtropical jet during EQBO phases causes more poleward propagation of synoptic-scale waves in the lower stratosphere, and thus more Rossby wave breaking events over Eurasia in late winter than during WQBO phases, further weakening and shifting the polar vortex in EQBO phases.
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