Synoptic eddy feedback and air–sea interaction in the North Atlantic region |
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Authors: | Lin-Lin Pan |
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Institution: | (1) International Pacific Research Center, University of Hawaii at Manoa, Honolulu, HI, USA;(2) Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA |
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Abstract: | This paper explores the role of synoptic eddy feedback in the air-sea interaction in the North Atlantic region, particularly
the interaction between the North Atlantic Oscillation (NAO) and the North Atlantic sea surface temperature anomalies (SSTA)
tripole. A linearized five-layer primitive equation atmospheric model with synoptic eddy and low-frequency flow (SELF) interaction
is coupled with a linearized oceanic mixed-layer model to investigate this issue. In this model, the “climatological” storm
track/activity (or synoptic eddy activity) is characterized in terms of spatial structures, variances, decay time scales and
propagation speeds through the complex empirical orthogonal function (CEOF) analysis on the observed data, which provides
a unique tool to investigate the role of synoptic eddy feedback in the North Atlantic air–sea coupling. Model experiments
show that the NAO-like atmospheric circulation anomalies can produce tripole-like SSTA in the North Atlantic Ocean, and the
tripole-like SSTA can excite a NAO-like dipole with an equivalent barotropic structure in the atmospheric circulation, which
suggests a positive feedback between the NAO and the SSTA tripole. This positive feedback makes the NAO/SSTA tripole-like
mode be the leading mode of the coupled dynamical system. The synoptic eddy feedback plays an essential role in the origin
of the NAO/SSTA tripole-like leading mode and the equivalent barotropic structure in the atmosphere. Without synoptic eddy
feedback, the atmosphere has a baroclinic structure in the response field to the tripole-like SSTA forcing, and the leading
mode of the dynamic system does not resemble NAO/SSTA tripole pattern. |
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