The switching between zonal and blocked mid-latitude atmospheric circulation: a dynamical system perspective

Atmospheric mid-latitude circulation is dominated by a zonal, westerly flow. Such a flow is generally symmetric, but it can be occasionally broken up by blocking anticyclones. The subsequent asymmetric flow can persist for several days. In this paper, we apply new mathematical tools based on the com...

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Veröffentlicht in:Climate dynamics Jg. 47; H. 5-6; S. 1587 - 1599
Hauptverfasser: Faranda, Davide, Masato, Giacomo, Moloney, Nicholas, Sato, Yuzuru, Daviaud, Francois, Dubrulle, Bérengère, Yiou, Pascal
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2016
Springer
Springer Nature B.V
Springer Verlag
Schlagworte:
Analysis
Anticyclones
Arctic region
Atmospheric circulation
Atmospheric models
basins
Brackish
Chaotic Dynamics
climate
Climate cycles
Climatology
Cyclones
Dynamic meteorology
Dynamical Systems
Earth and Environmental Science
Earth Sciences
Environmental Sciences
Geophysics/Geodesy
Global Changes
Latitude
Marine
Mathematics
mathematics and statistics
Nonlinear Sciences
North Atlantic Oscillation
Oceanography
United States
AN, North Atlantic
PN, Arctic
AN, North Atlantic, North Atlantic Oscillation
Arctic region
Mid-latitude circulation
Extremal index
Blocking index
ISSN:0930-7575, 1432-0894
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Zusammenfassung:Atmospheric mid-latitude circulation is dominated by a zonal, westerly flow. Such a flow is generally symmetric, but it can be occasionally broken up by blocking anticyclones. The subsequent asymmetric flow can persist for several days. In this paper, we apply new mathematical tools based on the computation of an extremal index in order to reexamine the dynamical mechanisms responsible for the transitions between zonal and blocked flows. We discard the claim that mid-latitude circulation features two distinct stable equilibria or chaotic regimes, in favor of a simpler mechanism that is well understood in dynamical systems theory: we identify the blocked flow as an unstable fixed point (or saddle point) of a single basin chaotic attractor, dominated by the westerlies regime. We also analyze the North Atlantic Oscillation and the Arctic Oscillation atmospheric indices, whose behavior is often associated with the transition between the two circulation regimes, and investigate analogies and differences with the bidimensional blocking indices. We find that the Arctic Oscillation index, which can be thought as a proxy for a hemispheric average of the Tibaldi–Molteni blocking index, tracks unstable fixed points. On the other hand, the North Atlantic Oscillation, representative only for local properties of the North Atlantic blocking dynamics, does not show any trace of the presence of unstable fixed points of the dynamics.
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ISSN:0930-7575
1432-0894
DOI:10.1007/s00382-015-2921-6