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Francis Codron

1. Introduction Quasi-annular patterns, often called annular modes, dominate atmospheric extratropical low-frequency variability ( Thompson and Wallace 1998 ). For both hemispheres, these modes are characterized by pressure anomalies of one sign over the polar region, surrounded by a band of opposing polarity with peak amplitude in the midlatitudes. They also appear as the favored response to a wide range of climate forcings, such as the observed trend in the Southern Hemisphere ( Thompson and

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I. G. Watterson

analysis of climate simulated by Mk3 for the twenty-second century are given in section 7 . Some discussion and conclusions regarding the annularity of both HLM and LLM are included in the sections. An overall summary is given in section 8 , and an assessment made of the merit of the term “annular mode” applied to both the simulated southern wind patterns. 2. Simulations by Mk3 a. Model The CSIRO Mk3 coupled atmosphere–ocean model is a substantial upgrade to Mk2, fully described by Gordon et al

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John Marshall, David Ferreira, J-M. Campin, and Daniel Enderton

variability giving it a slight, but not insignificant, enhancement of power at decadal time scales. It is not clear whether the coupled mechanism explored here is at work in the present climate, although if it were, the Southern Ocean would be a likely place to study. Finally one might hope that the key features of the aquaplanet climate described here might be somewhat insensitive to model formulation and implementation details. Unfortunately, the only other published result—that of Smith et al. (2006

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Robert X. Black and Brent A. McDaniel

weather ( Thompson and Wallace 2001 ; Baldwin et al. 2003 ). These annular modes occur in both the Northern and Southern Hemispheres [i.e., the Northern Annular Mode (NAM) and the Southern Annular Mode (SAM)] and over a wide range of time scales (weeks to decades). Most recent research examining connections between the stratospheric polar vortex and tropospheric circulation patterns has focused on either subseasonal variability (e.g., Limpasuvan et al. 2004 ; McDaniel and Black 2005 ) or long

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Michael J. Ring and R. Alan Plumb

contain vacillations of the zonal jet like those seen in the atmosphere. Annular modes have also been demonstrated in barotropic models (e.g., Vallis et al. 2004 ), dynamical cores of general circulation models (e.g., Yu and Hartmann 1993 ; Polvani and Kushner 2002 ; Kushner and Polvani 2004 ), aquaplanet GCMs (e.g., Cash et al. 2002 ), and full GCMs with more realistic oceans, topography, or chemistry schemes (e.g., Shindell et al. 1999 ; Kidson and Watterson 1999 ; Fyfe et al. 1999 ). As

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Thomas Jung and Peter B. Rhines

1. Introduction The Pacific and Atlantic maritime storm tracks represent amplification of transient cyclonic systems, shaped and guided by the stationary waves of the winter circulation. The earth’s orography, and the Atlantic and Pacific Ocean heat sources, both strongly influence the stationary waves (e.g., Held et al. 2002 ). Greenland, the largest island in the world, extends one-quarter of the distance between the North Pole and equator, or 2500 km. The solid earth is below sea level in

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O. Martius, C. Schwierz, and H. C. Davies

(anticyclonic) and LC2 (cyclonic). In the final stage of the anticyclonic life cycle (LC1), the form of the upper-level wave changes as it becomes exposed to the anticyclonic shear on the southern edge of the jet. It elongates in the northeast–southwest (NE–SW) direction and narrows in its zonal extent ( THM ), and thereafter it often breaks up into upper-level cutoff vortices ( THM ; Appenzeller et al. 1996 ). During the cyclonic life cycle (LC2), the disturbance remains on the cyclonically sheared side

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Cegeon J. Chan, R. Alan Plumb, and Ivana Cerovecki

, 99 pp . Lorenz , D. J. , and D. L. Hartmann , 2001 : Eddy–zonal flow feedback in the Southern Hemisphere. J. Atmos. Sci. , 58 , 3312 – 3327 . Marshall , J. , A. Adcroft , C. Hill , L. Perelman , and C. Heisey , 1997a : A finite-volume, incompressible Navier Stokes model for studies of the ocean on parallel computers. J. Geophys. Res. , 102 , 5753 – 5766 . Marshall , J. , C. Hill , L. Perelman , and A. Adcroft , 1997b : Hydrostatic, quasi-hydrostatic, and

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P. H. Haynes, D. A. Poet, and E. F. Shuckburgh

encodes the transport effect of the longitudinally varying part of the flow. We may consider this transport effect by following the evolution of a second tracer that is advected by a modified flow obtained by removing the longitudinal mean part from the full flow [a similar study has been conducted using velocity fields from the surface Southern Ocean by Marshall et al. (2006) ]. The effective diffusivity calculated from this second tracer is shown in Fig. 7d . This is strikingly different from the

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Edwin P. Gerber and Geoffrey K. Vallis

damping time scale of anomalies (8.9 days), providing some evidence of a feedback between the eddies and the large-scale flow. They propose a feedback based on changes in the index of refraction associated with shifts in the extratropical jet, which allow the jet to shape the higher frequency eddies. Independently, Kidson and Watterson (1999) and Watterson (2002) consider the behavior of the zonal index in the Southern Hemisphere of an atmospheric GCM coupled to a mixed layer ocean. While they

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