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

mean flows and recognized its persistent characteristics. A peculiar feature found by Yoden and Yamada (1993) is that, in addition to the appearance of the banded structure of zonal mean flows, intense easterly (retrograde) circumpolar jets tend to emerge especially at large rotation rate. The appearance of an easterly circumpolar jet has been confirmed as a robust feature in decaying turbulence, while in forced turbulence, its appearance seems to depend on the forcing scale. When the forcing

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Yuji Kitamura and Keiichi Ishioka

fundamentals for examining large-scale structures of atmospheric motions. Two-dimensional turbulence and its rotational effects have been studied to investigate the nonlinear dynamics in the atmosphere and ocean by many authors. Rhines (1975) first found that a zonal structure spontaneously becomes dominant in 2D turbulence on a β plane. The meridional scale of the zonal jet is characterized by the scale L β = 2 U 0 / β ( U 0 stands for a representative velocity), which is called the Rhines scale

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Shuguang Wang and Fuqing Zhang

1. Introduction Atmospheric jets are known to generate gravity waves. Gravity wave emission in the exit region of jets has been documented in many studies, such as those based on observations (e.g., Uccellini and Koch 1987 ; Koch and Dorian 1988 ; Schneider 1990 ; Hertzog et al. 2001 ; Zhang et al. 2001 ; Plougonven and Teitelbaum 2003 ; Wu and Zhang 2004 ; Koch et al. 2005 ) and on numerical simulations of gravity waves within baroclinic life cycles ( O’Sullivan and Dunkerton 1995

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Mark D. Fruman, Bach Lien Hua, and Richard Schopp

1. Introduction Understanding the formation and evolution of zonally symmetric zonal flows is a central problem in the theory of atmospheric and oceanic circulation. Examples include the equatorial jets on Jupiter ( Vasavada and Showman 2005 ) and the zonal jets in the circulations of all three equatorial oceans ( Ollitrault et al. 2006 ; Richards et al. 2006 ). In the latter case, the jets have a rich latitudinal and vertical structure not easily explained by traditional arguments. The

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Dave Broutman, Stephen D. Eckermann, and James W. Rottman

1. Introduction Mountain waves propagate to great heights in the atmosphere (see the review by Fritts and Alexander 2003 ), at times reaching the mesosphere and lower thermosphere ( Bacmeister 1993 ; Eckermann et al. 2007 ). The propagation can be interrupted by wind jets, which produce evanescent layers that partially reflect and partially transmit the waves (e.g., Nault and Sutherland 2008 , hereafter NaSu ). Above the wind jet, the partially transmitted waves can continue to grow with

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Sukyoung Lee

central assumption of weakly nonlinear theory. However, the assumption of homogeneous turbulence is at odds with the prominence of westerly jets and attendant nonzero time-mean turbulent eddy vorticity fluxes ( Robinson 2006 ); to use the nonlinear stability theorem, Shepherd (1988) assumed that the flow in question is subject to potential vorticity damping, which implies that the top of the atmosphere is subject to the same Ekman damping rate as the bottom of the atmosphere. Although these papers

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Thomas R. Parish and Larry D. Oolman

1. Introduction The summertime Great Plains low-level jet (LLJ) of the central United States is one of the most intensely studied mesoscale features of the past 50 years (e.g., Lettau and Davidson 1957 ; Hoecker 1963 ; Bonner 1968 ). Wind profiles at Great Plains sites during the daytime show weak southerly winds, often less than 5 m s −1 . Speeds increase significantly in the hours after sunset with an LLJ developing at levels 300–800 m above the ground. LLJ wind speeds reach a maximum

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Jie Song, Wen Zhou, Xin Wang, and Chongyin Li

storm track in observations and in ideal model simulations ( Vallis et al. 2004 ). In the zonal direction, a more zonally “annular” (localized) AM is associated with a more zonally uniform (localized) storm track. Recently, some studies have also revealed that the zonal pattern of the AM is strongly influenced by the boundary topography and land–sea contrast ( Cash et al. 2005 ; Körnich et al. 2006 ; Gerber and Vallis 2009 ). In this study, we highlight the importance of the strong subtropical jet

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Xianan Jiang, Ngar-Cheung Lau, Isaac M. Held, and Jeffrey J. Ploshay

1. Introduction During the summer months from April to September, the Great Plains of the United States are characterized by the frequent occurrence of a southerly low-level jet (LLJ). This LLJ is mainly confined in the boundary layer with maximum wind speeds typically at 500–1000 m above the ground. The jet exhibits strong diurnal oscillation, with the strongest wind speed mostly occurring during the night. This Great Plains LLJ has been intensively documented during the past decades (e

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Amanda K. O’Rourke and Geoffrey K. Vallis

1. Introduction The identification of the subtropical and eddy-driven jets as two related, but separate and distinct, features of the midlatitude atmosphere has received increasing research attention over the past decade ( Lee and Kim 2003 ; Kim and Lee 2004 ; Vallis 2006 ). The classical approach to the general circulation of the midlatitude atmosphere is to describe the movement of a single “jet stream” corresponding to the single maximum in zonal-mean zonal wind. However, this single-jet

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