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contributor authorFerreira, David
contributor authorFrankignoul, Claude
date accessioned2017-06-09T17:00:26Z
date available2017-06-09T17:00:26Z
date copyright2005/04/01
date issued2005
identifier issn0894-8755
identifier otherams-77794.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4220391
description abstractTo study the transient atmospheric response to midlatitude SST anomalies, a three-layer quasigeostrophic (QG) model coupled to a slab oceanic mixed layer in the North Atlantic is used. As diagnosed from a coupled run in perpetual winter conditions, the first two modes of SST variability are linked to the model North Atlantic Oscillation (NAO) and eastern Atlantic pattern (EAP), respectively, the dominant atmospheric modes in the Atlantic sector. The two SST anomaly patterns are then prescribed as fixed anomalous boundary conditions for the model atmosphere, and its transient responses are established from a large ensemble of simulations. In both cases, the tendency of the air?sea heat fluxes to damp the SST anomalies results in an anomalous diabatic heating of the atmosphere that, in turn, forces a baroclinic response, as predicted by linear theory. This initial response rapidly modifies the transient eddy activity and thus the convergence of eddy momentum and heat fluxes. The latter transforms the baroclinic response into a growing barotropic one that resembles the atmospheric mode that had created the SST anomaly in the coupled run and is thus associated with a positive feedback. The total adjustment time is as long as 3?4 months for the NAO-like response and 1?2 months for the EAP-like one. The positive feedback, in both cases, is dependent on the polarity of the SST anomaly, but is stronger in the NAO case, thereby contributing to its predominance at low frequency in the coupled system. However, the feedback is too weak to lead to an instability of the atmospheric modes and primarily results in an increase of their amplitude and persistence and a weakening of the heat flux damping of the SST anomaly.
publisherAmerican Meteorological Society
titleThe Transient Atmospheric Response to Midlatitude SST Anomalies
typeJournal Paper
journal volume18
journal issue7
journal titleJournal of Climate
identifier doi10.1175/JCLI-3313.1
journal fristpage1049
journal lastpage1067
treeJournal of Climate:;2005:;volume( 018 ):;issue: 007
contenttypeFulltext


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