Atmospheric GCM response to extratropical SST anomalies: Synthesis and evaluation

Publication Type  Journal Article
Year of Publication  2002
Authors  Kushnir, Y.; Robinson, W. A.; Blade, I.; Hall, N. M. J.; Peng, S.; Sutton, R.
Journal Title  Journal of Climate
Volume  15
Issue  16
Pages  2233-2256
Journal Date  Aug 15
ISBN Number  0894-8755
Accession Number  ISI:000177529400007
Key Words  sea-surface temperature; north-atlantic oscillation; low-frequency variability; decadal climate variability; general-circulation models; level pressure anomalies; heat-flux anomalies; pacific-ocean; interannual variability; interdecadal variability

The advances in our understanding of extratropical atmosphere-ocean interaction over the past decade and a half are examined, focusing on the atmospheric response to sea surface temperature anomalies. The main goal of the paper is to assess what was learned from general circulation model (GCM) experiments over the recent two decades or so. Observational evidence regarding the nature of the interaction and dynamical theory of atmospheric anomalies forced by surface thermal anomalies is reviewed. Three types of GCM experiments used to address this problem are then examined: models with fixed climatological conditions and idealized, stationary SST anomalies; models with seasonally evolving climatology forced with realistic. time-varying SST anomalies; and models coupled to an interactive ocean. From representative recent studies, it is argued that the extratropical atmosphere does respond to changes in underlying SST although the response is small compared to internal (unforced) variability. Two types of interactions govern the response. One is an eddy-mediated process, in which a baroclinic response to thermal forcing induces and combines with changes in the position or strength of the storm tracks. This process can lead to an equivalent barotropic response that feeds back positively on the ocean mixed layer temperature. The other is a linear, thermodynamic interaction in which an equivalent-barotropic low-frequency atmospheric anomaly forces a change in SST and then experiences reduced surface thermal damping due to the SST adjustment. Both processes contribute to an increase in variance and persistence of low-frequency atmospheric anomalies and, in fact, may act together in the natural system.


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URL  <Go to ISI>://000177529400007