Seminar
How Stationary Waves Influence the Northern Annular Mode Response to Surface Forcing
Paul Kushner, Department of Physics, University of Toronto
Wednesday, June 1, 2011, 3:30 pm Mountain Time
DSRC 2A305
Abstract
In this seminar, I will discuss the dynamics of the Northern Annular Mode (NAM) response to surface forcing in the tropics and extratropics. In observations and GCMs, a large portion of wintertime tropospheric NAM variability is tied to variability in the amount of wave activity that propagates into the Arctic stratosphere. A large portion of this wave activity variability can in turn be diagnosed in terms of constructive and destructive interference of planetary wave anomalies with the stationary (climatological) planetary wave field. My collaborators and I have extensively explored this interference effect in general circulation models forced by prescribed perturbations at the ocean and land surface. When this interference effect dominates, for a given phase and amplitude of the wave response to surface forcing, the zonal mean NAM response can be predicted. Two case studies will be presented, involving the connection between boreal autumn snow cover extent over Eurasia and the wintertime NAM, as well as the connection between tropical sea surface temperature forcing and the NAM. For recent papers on this topic, see publications with Chris Fletcher and Karen Smith at Prof. Kushner's website.
Bio:
Ph.D. University of Toronto, 1995
Visiting Scientist and Research Scientist at NOAA/GFDL, 1995-2003
Professor at Toronto since 2004
Sabbatical at NCAR Mesa Lab 2011
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