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Aditi Sheshadri, R. Alan Plumb, and Edwin P. Gerber

of Northern Hemisphere stratospheric final warming events . J. Atmos. Sci. , 64 , 2932 – 2946 , doi: 10.1175/JAS3981.1 . Black , R. X. , and B. A. McDaniel , 2007b : Interannual variability in the Southern Hemisphere circulation organized by stratospheric final warming events . J. Atmos. Sci. , 64 , 2968 – 2974 , doi: 10.1175/JAS3979.1 . Black , R. X. , B. A. McDaniel , and W. A. Robinson , 2006 : Stratosphere–troposphere coupling during spring onset . J. Climate , 19

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Chen Wei, Oliver Bühler, and Esteban G. Tabak

; therefore, the wave structure in the troposphere cannot be approximated well using upward-propagating waves alone. Conversely, solving for the wave field using the simplified approach in the presence of back-reflection at the tropopause leads to unphysical incoming internal waves in the upper atmosphere, which clearly do no satisfy the radiation condition there. The key factor is to enforce the proper radiation condition in the upper atmosphere as well as the kinematic and dynamic boundary conditions at

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Joowan Kim and Seok-Woo Son

1. Introduction In the tropics, the thermal boundary between the stratosphere and troposphere is well defined by the coldest level, the so-called cold-point tropopause (CPT). Thermal characteristics of the CPT have been extensively examined as they play a crucial role in stratosphere–troposphere coupling and exchange ( Holton et al. 1995 ). For instance, transport of water vapor from the troposphere to the stratosphere is to a great extent controlled by temperature at the CPT. Because the air

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Isla R. Simpson, Michael Blackburn, and Joanna D. Haigh

coordinate. Triangular truncation at wavenumber 42 is used and there are 15 levels between the surface and σ = 0.0185. Unlike some sGCMs used to investigate stratosphere–troposphere coupling, the model intentionally does not include a fully resolved stratosphere and does not exhibit a stratospheric polar vortex. The mean state is maintained by Newtonian relaxation of temperature toward a zonally symmetric equilibrium state. In the original configuration used in HBD05 and SBH09 , this relaxation

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Francesco d’Ovidio, Emily Shuckburgh, and Bernard Legras

1. Introduction It is now well established that the distribution of tracers in the upper troposphere and the lower stratosphere (UTLS) strongly depends on the transport and mixing properties of the flow. It is also well established that the dominant isentropic motion induces a chaotic type of tracer advection, giving rise to strongly inhomogeneous stirring (and thus, in the presence of diffusion, inhomogeneous mixing). 1 This segregates tracers into distinct well-mixed reservoirs separated by

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C. Schnadt Poberaj, J. Staehelin, and D. Brunner

propagate into the middle atmosphere ( Charney and Drazin 1961 ). c. Coupling to tropospheric dynamics In the troposphere, there is a rich spectrum of extratropical waves at the synoptic and planetary scale. In the SH, the absence of mountain chains locking the phase of planetary waves implies that atmospheric variability is mostly accounted for by transient (traveling) waves ( James 1994 ), and that stationary wave amplitudes are much smaller than their northern counterparts ( van Loon and Jenne 1972

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Murry L. Salby and Patrick F. Callaghan

1. Introduction In the tropical stratosphere, the circulation is dominated by the quasi-biennial oscillation (QBO) of equatorial wind. In the tropical troposphere, it is characterized by the Hadley circulation, which is forced by convection and the release of latent heat. Historically, these two circulations have been regarded as independent. In the classical theory of the QBO, the stratospheric circulation depends upon the tropospheric circulation only indirectly, through vertically

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Peter Hitchcock, Theodore G. Shepherd, Masakazu Taguchi, Shigeo Yoden, and Shunsuke Noguchi

1. Introduction The lower polar stratosphere has been identified as a key region for the two-way coupling between the stratosphere and the troposphere. Circulation anomalies in the stratospheric polar vortices in both hemispheres have been shown to influence the extratropical tropospheric jets, whether they are caused by, for instance, ozone depletion in the Southern Hemisphere ( Thompson and Solomon 2002 ; Son et al. 2008 ) or sudden warmings in the Northern Hemisphere ( Baldwin and Dunkerton

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Masakazu Taguchi

) demonstrate enhanced seasonal forecast skill for the tropospheric circulation in the Northern Hemisphere following onset of SSWs. Regarding the Southern Hemisphere spring (when stratospheric variability is large), Roff et al. (2011) obtain better forecast skill in the troposphere several weeks after the initialization in a higher-vertical-resolution model than in a lower-resolution model. Comparing five seasonal forecasting models, Maycock et al. (2011) show that although the models underestimate the

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Peter Hitchcock and Peter H. Haynes

, and a result analogous to (8) holds for other nudging geometries. Within the context of experiments studying stratosphere–troposphere coupling, we are most interested in the winds induced throughout the atmosphere by stratospheric wave driving, as a result of the nonlocality of B . One central issue to be addressed in this paper is the nature of the differences between the winds induced by the stratospheric wave driving (defined by some appropriate projection operator) in the reference

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