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The downward influence of stratospheric sudden warmings

dc.creatorHitchcock, Adam Peter
dc.creatorSimpson, Isla R
dc.date.accessioned2018-11-24T23:17:50Z
dc.date.available2014-07-14T16:12:23Z
dc.date.available2018-11-24T23:17:50Z
dc.date.issued2014-07-14
dc.identifierhttps://www.repository.cam.ac.uk/handle/1810/245496
dc.identifier.urihttp://repository.aust.edu.ng/xmlui/handle/123456789/3177
dc.description.abstractThe coupling between the stratosphere and the troposphere following two major stratospheric sudden warmings is studied in the Canadian Middle Atmosphere Model using a nudging technique by which the zonal mean evolution of the reference sudden warmings are artificially induced in an ∼100 member ensemble spun off from a control simulation. Both reference warmings are taken from a freely-running integration of the model. One event is a displacement, the other a split, and both are followed by extended recoveries in the lower stratosphere. The methodology permits a statistically robust study of their influence on the troposphere below. The nudged ensembles exhibit a tropospheric annular-mode response closely analogous to that seen in observations, confirming the downward influence of sudden warmings on the troposphere in a comprehensive model. This tropospheric response coincides more closely with the lower stratospheric annular mode anomalies than with the mid-stratospheric wind reversal. In addition to the expected synoptic scale eddy feedback, the planetary-scale eddies also reinforce the tropospheric wind changes, apparently responding directly to the stratospheric anomalies. Furthermore, despite the zonal symmetry of the stratospheric perturbation, a highly zonally asymmetric near surface response is produced, corresponding to a strongly negative phase of the North Atlantic Oscillation with a much weaker response over the Pacific basin which matches composites of sudden warmings from the ERA-Interim reanalysis. The Coupled Model Intercomparison Project phase 5 models exhibit a similar response, though in most models its magnitude is under-represented.
dc.languageen
dc.publisherJournal of the Atmospheric Sciences
dc.rightsDSpace@Cambridge license
dc.titleThe downward influence of stratospheric sudden warmings
dc.typeArticle


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