Repository logo
 

The downward influence of stratospheric sudden warmings


Type

Article

Change log

Authors

Hitchcock, P 
Simpson, IR 

Abstract

jats:titleAbstract</jats:title> jats:pThe 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 is 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.</jats:p> jats:pThe 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 midstratospheric 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.</jats:p> jats:pFurthermore, 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 that matches composites of sudden warmings from the Interim ECMWF Re-Analysis (ERA-Interim). Phase 5 of the Coupled Model Intercomparison Project models exhibit a similar response, though in most models the response’s magnitude is underrepresented.</jats:p>

Description

Keywords

37 Earth Sciences, 3708 Oceanography, 3701 Atmospheric Sciences

Journal Title

Journal of the Atmospheric Sciences

Conference Name

Journal ISSN

0022-4928
1520-0469

Volume Title

Publisher

American Meteorological Society

Rights

DSpace@Cambridge license
Sponsorship
European Research Council (267760)
PH acknowledges support from ERC project no 267760 - ACCI and an NSERC Postdoctoral Fellowship. IRS was supported by a Lamont-Doherty Earth Observatory postdoctoral fellowship and NSF award AGS-1317469. T