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Yasuko Hio and Shigeo Yoden

1. Introduction This paper considers nonlinear dynamics of an idealized winter polar vortex in the Southern Hemisphere (SH) stratosphere with a barotropic model on a spherical domain. The SH polar vortex is stronger and less disturbed compared to that of the Northern Hemisphere. In other words, the zonal-mean zonal flow is stronger and planetary waves are weaker in the SH due to weaker forcing of the planetary waves in the troposphere. As a result, a major stratospheric sudden warming event had

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Yoshi-Yuki Hayashi, Seiya Nishizawa, Shin-ichi Takehiro, Michio Yamada, Keiichi Ishioka, and Shigeo Yoden

simulation. We had to wait about 15 yr, until a certain level of completion was achieved in the development of global atmospheric models along with a great improvement of computer resource availability, to be able to tackle the problem of two-dimensional turbulence on a sphere. The bright side to this blank period was that images of Rossby wave propagation on a sphere had been accumulated, as exemplified in such works as Grose and Hoskins (1979) and Hoskins and Karoly (1981) , with some remarks by

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M. L. R. Liberato, J. M. Castanheira, L. de la Torre, C. C. DaCamara, and L. Gimeno

point of view of the energy associated with the forcing waves. The main goal of this work is therefore to perform a diagnostic study of the total (i.e., kinetic + available potential) energy associated with the planetary waves that force the vortex dynamics. The analysis is based on a three-dimensional (3D) normal mode decomposition of the atmospheric global circulation, which is partitioned into planetary Rossby waves and inertio–gravity waves, both types of waves possessing barotropic and

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Peter L. Read, Yasuhiro H. Yamazaki, Stephen R. Lewis, Paul D. Williams, Robin Wordsworth, Kuniko Miki-Yamazaki, Joël Sommeria, and Henri Didelle

2003 ). This has led to the notional concept of a rotating fluid that is stirred on small scales and within which kinetic energy (KE) cascades to larger scales via nonlinear interactions. The formation of jetlike structures occurs through the effects of anisotropies introduced by the presence of a “planetary vorticity gradient,” because of which eddies of a large enough scale are constrained to propagate zonally in a dispersive manner reminiscent of Rossby waves. This results eventually in an

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D. G. Dritschel and M. E. McIntyre

1. Introduction Chaotic flows in stratified, rotating fluid systems like planetary atmospheres and oceans are often called “turbulent.” However, in such systems there is no such thing as turbulence without waves, a point well brought out in the celebrated paper of Rhines (1975) . One way to appreciate the point is to note that such systems always have background gradients of potential vorticity (PV) and then consider the implications for the momentum and angular momentum budgets. As will be

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P. B. Rhines

all lateral scales and is a potent source of circulation structures, from planetary-scale motions to much finer scales. The literature concentrates particularly on hemisphere-filling stationary waves on the one hand (e.g., Held et al. 2002 ), and lee waves and turbulent wakes on the other. Potential vorticity conservation provides, as in many areas of synoptic dynamics, a logical framework with which to proceed. In this paper we present experiments, mostly from our geophysical fluid dynamics (GFD

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Robert X. Black and Brent A. McDaniel

winter terminates with a relatively rapid breakdown of the polar vortex known as the stratospheric final warming (SFW), marking the final transition from westerlies to easterlies in the extratropical stratosphere. There is considerable interannual variability in the timing of SFW events ( Waugh and Rong 2002 ) since they are sensitive to the preexisting stratospheric flow structure and variations in the upward propagation of tropospheric planetary waves ( Waugh et al. 1999 ). SFW events are more

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Shin Takehiro, Michio Yamada, and Yoshi-Yuki Hayashi

1. Introduction Banded structures and associated zonal flows of planetary atmospheres, typically observed in Jovian planets, are one of the prominent planetary-scale fluid dynamical phenomena and have attracted the interests of many researchers. Some of the studies have sought their generation and maintenance mechanism in deep convective motion (e.g., Busse 1983 ; Heimpel et al. 2005 ), while others have extensively discussed the dynamical properties of two-dimensional fluid motions in a

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Yuji Kitamura and Keiichi Ishioka

and in which the order between the linear and nonlinear terms is comparable. His pioneering study has motivated studies of rotating 2D turbulence as a problem of pattern formation. Vallis and Maltrud (1993) showed that the wave-turbulence boundary in wavenumber space has the smallest meridional wavenumber at the k x = 0 axis ( k x represents a zonal wavenumber) because of the anisotropy of the frequency of Rossby waves. They also elucidated the mechanism for the predominance of zonally

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

States at the eastern flanks of the planetary ridges. These results confirm observations from earlier studies that note a preference for cyclonically breaking waves in flow configurations where the jet is shifted to the south and the opposite for anticyclonically breaking waves ( Hartmann 1995 ; Akahori and Yoden 1997 ). The results also agree well with the idealized findings of Orlanski (2003) . The cyclonic streamers are located preferentially in areas where the surface baroclinicity is strong

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