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Stratospheric sudden warmings in an idealized GCM

Author(s): Jucker, Martin; Fueglistaler, Stephan; Vallis, Geoffrey K

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Abstract: An idealized general circulation model (GCM) with an analytically described Newtonian cooling term is employed to study the occurrence rate of sudden stratospheric warmings (SSWs) over a wide range of parameters. In particular, the sensitivity of the SSW occurrence rates to orographic forcing and both relaxation temperature and damping rate is evaluated. The stronger the orographic forcing and the weaker the radiative forcing (in both temperature and damping rate), the higher the SSW frequency. The separate effects of the damping rates at low and high latitudes are somewhat more complex. Generally, lower damping rates result in higher SSW frequency. However, if the low‐ and high‐latitude damping rates are not the same, SSW frequency tends to be most sensitive to a fractional change in the lower of the two damping rates. In addition, the effect of the damping rates on the stratospheric residual circulation is investigated. It is found that higher high‐latitude damping rate results in deeper but narrower circulation, whereas higher low‐latitude damping rates cause strengthening of the stream function in the tropical midstratosphere to upper stratosphere. Finally, the relation between easily measured and compared climatological fields and the SSW occurrence rate is determined. The average stratospheric polar zonal mean zonal wind shows a strong anticorrelation with the SSW frequency. In the troposphere, there is a high correlation between the meridional temperature gradient and SSW frequency, suggesting that the strength of synoptic activity in the troposphere may be an important influence on SSW occurrence.
Publication Date: 30-Aug-2014
Electronic Publication Date: 6-Oct-2014
Citation: Jucker, Martin, Stephan Fueglistaler, and Geoffrey K. Vallis. "Stratospheric sudden warmings in an idealized GCM." Journal of Geophysical Research: Atmospheres 119, no. 19 (2014): 11054-11064. doi:10.1002/2014JD022170.
DOI: doi:10.1002/2014JD022170
ISSN: 2169-897X
EISSN: 2169-8996
Pages: 11054-11064
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Geophysical Research: Atmospheres
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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