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Yutian Wu and Olivier Pauluis

1. Introduction The question of what determines the extratropical tropopause height is of fundamental importance to the general circulation of the atmosphere. It is generally believed that the height of the tropopause is controlled by both the radiative constraint from the stratosphere and the dynamical constraint stemming from the dry baroclinic instability in the tropospheric midlatitudes ( Held 1982 ). Recent studies have also indicated the importance of the stratospheric large

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

1. Introduction Tropopause-level jet streams are accompanied by a steplike decrease in the height of the tropopause itself, and there is an accompanying strong lateral gradient of the potential vorticity (PV) across the step. Also, on isentropic surfaces that traverse the step from the troposphere to the stratosphere, this PV gradient, ∼10 PV units (PVU; where 1 PVU = 1 × 10 −6 m 2 s −1 K kg −1 ) in 1000 km ( Davies and Rossa 1998 ; Schwierz et al. 2004 ), takes the form of a narrow and

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Steven M. Cavallo and Gregory J. Hakim

1. Introduction Tropopause polar vortices (TPVs) are a commonly observed feature of the Arctic that exist on daily to monthly time scales. Although both cyclones and anticyclones are observed, we focus here on cyclonic TPVs because these features may excite surface cyclones and, through their cloud fields, affect the Arctic radiation budget. Although numerous and long lived, little is known with regard to factors that control their intensity. These upper-level disturbances are defined by closed

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Pablo Zurita-Gotor and Geoffrey K. Vallis

1. Introduction Although the tropopause is one of the most important features of the atmospheric circulation, our understanding of the processes that control its height remains incomplete. Indeed, there is no unique definition of the tropopause. Conceptually, the tropopause may be thought of as the transition region separating the dynamically active troposphere, a layer in which mixing by the air motion takes place on time scales of days, and a stratosphere that is much more quiescent in

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Jung-Hee Ryu, Sukyoung Lee, and Seok-Woo Son

1. Introduction The established view is that the height of the time- mean tropical tropopause is controlled by deep convection up to a height of ≈12–13 km ( Riehl and Malkus 1958 ), and that radiative balance explains the continued decrease in temperature up to the cold-point tropopause at ≈17 km. In contrast, the temporal variability of the tropical tropopause height, and related variables such as tropopause temperature, are known to be associated with fluctuations in upwelling induced by

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Thomas Birner

1. Introduction The height of the tropopause is often considered to be set primarily by the combined effects of a dynamically active troposphere and a stratosphere in near-radiative equilibrium (e.g., Manabe and Strickler 1964 ; Held 1982 ; Thuburn and Craig 1997 ; Schneider 2007 ). Held (1982) introduced the concept of separating dynamical and radiative constraints to determine tropopause height. In one form of this concept, one assumes a given surface temperature and (constant

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Jacob Haqq-Misra, Sukyoung Lee, and Dargan M. W. Frierson

1. Introduction The boundary between the troposphere and stratosphere is known as the tropopause and has been empirically characterized in a number of ways that include an abrupt change of atmospheric lapse rate, an increase in static stability, a rapid change in potential vorticity, and a difference in chemical composition. Prominent atmospheric circulations, such as the Hadley circulation, as well as most weather systems are confined to the troposphere, and air parcels in the troposphere that

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R. Plougonven and J. Vanneste

1. Introduction Tropopause motion plays a crucial part in the dynamics of the atmosphere. Important features of the tropospheric and lower-stratospheric circulation at midlatitude can indeed be well described by considering only balanced motion at the tropopause, near the ground, and their interactions ( Hoskins et al. 1985 ). Furthermore, the role of the tropopause as a barrier to transport makes it crucial for the distribution of atmospheric tracers such as water vapor or ozone. The simplest

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Pengfei Xia, Yingying Shan, Shirong Ye, and Weiping Jiang

1. Introduction The tropopause is a transitional layer in the atmosphere that connects the troposphere and the stratosphere. It is a fundamental structure of the atmosphere that affects the exchange of materials and energy between the troposphere and the stratosphere ( Hoinka 1997 ). As such, the tropopause is the key transition layer between the upper troposphere and the lower stratosphere, and its characteristics are linked to stratosphere–troposphere exchange (STE), and climate

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Seok-Woo Son, Sukyoung Lee, and Steven B. Feldstein

1. Introduction The tropopause is a transition region between the troposphere and the stratosphere, where dynamic and thermodynamic properties rapidly change. Across the tropopause, there is an exchange of mass, moisture, and chemical constituents. Since slight changes in the exchanged amount of moisture and chemical constituents may result in significant changes in the global climate, precise knowledge of the spatial and temporal structure of the tropopause is beneficial ( Holton et al. 1995

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