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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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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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Xi Chen
,
Luolin Wu
,
Xiaoyang Chen
,
Yan Zhang
,
Jianping Guo
,
Sarah Safieddine
,
Fuxiang Huang
, and
Xuemei Wang

, minima in O 3 ( Park et al. 2007 ), and high values of SO 2 and aerosols ( Yu et al. 2017 ; Vernier et al. 2011 , 2015 ; Lamarque et al. 2012 ) within the anticyclone in the upper troposphere and lower stratosphere (UTLS) throughout summer. This is a result of the combined effects of deep convection and anticyclone caused by the Asian monsoon ( Ploeger et al. 2017 ). Pollutants can be transported from the boundary layer to the upper troposphere within 30 min, or even less, due to strong updrafts

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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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Charles Chemel
,
Maria R. Russo
,
John A. Pyle
,
Ranjeet S. Sokhi
, and
Cornelius Schiller

1. Introduction The characteristics of the upper-troposphere/lower-stratosphere (UT/LS) region are intrinsically determined by those of both spheres. The balance of processes that regulate its dynamical, radiative, and chemical characteristics is at the heart of the debate on UT/LS exchanges. In particular, the quantification of the respective role of convective overturning in the troposphere and radiative and/or diabatic overturning in the stratosphere in determining the entry of atmospheric

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Peter Hitchcock
and
Theodore G. Shepherd

1. Introduction The Arctic polar vortex is one of the most variable components of the zonal-mean circulation of the atmosphere on intraseasonal to interannual time scales. The radiatively generated vortex is disrupted intermittently and irregularly by planetary-scale Rossby waves produced by the troposphere below. In the most spectacular cases, these bursts result in major stratospheric sudden warmings, during which the zonal-mean westerly winds reverse. For up to 3 months following roughly

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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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Rei Ueyama
,
Edwin P. Gerber
,
John M. Wallace
, and
Dargan M. W. Frierson

45°N. These parameter settings have been shown to produce realistic troposphere–stratosphere coupling ( Gerber and Polvani 2009 ) and a realistic BDC ( Gerber 2012 ). The reader is referred to these papers for a more detailed description of the model. The 6-hourly global European Centre for Medium-Range Weather Forecasts Interim Re-Analysis (ERA-Interim; Dee et al. 2011 ) data are analyzed for the 32-yr period from 1 January 1979 to 31 December 2010. The data are gridded at 1.5° latitude by 1

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