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dc.contributor.authorHatfield, Luke A.
dc.contributor.authorScott, Richard K.
dc.identifier.citationHatfield , L A & Scott , R K 2019 , ' Internal interannual variability of the winter polar vortex in a simple model of the seasonally evolving stratosphere ' , Quarterly Journal of the Royal Meteorological Society , vol. Early View .
dc.identifier.otherPURE: 259545971
dc.identifier.otherPURE UUID: 226b701a-7996-4625-a523-74f625c638e6
dc.identifier.otherRIS: urn:32613D5D4B288AFB5FB253492F74C8F9
dc.identifier.otherORCID: /0000-0001-5624-5128/work/60427157
dc.identifier.otherScopus: 85070664084
dc.identifier.otherWOS: 000480084000001
dc.description.abstractWe investigate persistent low-frequency variability of the stratospheric winter polar vortex in a rotating spherical shallow-water model under the action of topographic wave-forcing and radiative cooling to a simple time-varying equilibrium state representative of the seasonal cycle in solar heating. A range of modes of variability is obtained, dependent on wave forcing amplitude and characterized by the distribution of quiescent and disturbed winters, defined as winters in which the vortex is either close to radiative equilibrium, with low planetary wave amplitude, or else strongly disturbed from equilibrium by the wave forcing. At low forcing amplitude the vortex is typically quiescent every year, while at higher amplitude it is typically disturbed; in both cases there is little year-to-year variation of the vortex state. For a range of intermediate forcing amplitudes, however, the vortex transitions between quiescent and disturbed states from one winter to the next with a persistent and well-defined pattern of variability. To investigate the extent to which the low-frequency variability found here may be explained in terms of a low-latitude flywheel mechanism, we conduct additional experiments varying a linear drag on the zonal mean flow in the tropics and find that sufficiently strong drag can completely suppress the variability. The robustness of the variability is demonstrated by further experiments using a modified radiative equilibrium profile, associated with a tropical westerly flow: similar variability is obtained but the modified profile is less effective at constraining the tropical flow from a persistent easterly acceleration.
dc.relation.ispartofQuarterly Journal of the Royal Meteorological Societyen
dc.rights© 2019, Royal Meteorological Society. This work has been made available online in accordance with the publisher's policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at
dc.subjectLow-frequency variabilityen
dc.subjectPolar vortexen
dc.subjectSeasonal cycleen
dc.subjectShallow-water modelen
dc.subjectQA Mathematicsen
dc.subjectQC Physicsen
dc.titleInternal interannual variability of the winter polar vortex in a simple model of the seasonally evolving stratosphereen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews.Applied Mathematicsen
dc.description.statusPeer revieweden

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