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Damien Irving and Ian Simmonds

1. Introduction The relationship between mid- to upper-tropospheric planetary wave activity and regional climate variability in the Northern Hemisphere (NH) has received a great deal of attention in recent times, as researchers try to better understand the links between the Arctic amplification and midlatitude weather (e.g., Cohen et al. 2014 ; Screen and Simmonds 2014 ). While the meridional temperature gradient has not undergone such dramatic changes in the Southern Hemisphere (SH), this

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Dehai Luo, Tingting Gong, and Yina Diao

(2006a , hereafter AM06a ) noted that the planetary wave breaking (PWB) that occurs in the subtropical Atlantic may amplify the positive NAO. On the other hand, it has been demonstrated in observational studies that the NAO phenomenon is characterized by a meridional displacement of the upper-tropospheric jet where positive and negative phases correspond, respectively, to the northward and southward movements of a westerly jet ( B04 ; F04 ; Riviere and Orlanski 2007 ), thus concluding that wave

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A. Hannachi

1. Background and motivation The dynamics of low-frequency variability have been, and still are, the focus of many research studies. This continuous interest is driven by the need to understand the dynamics of tropospheric planetary waves and other synoptic patterns such as blocking for predictability. The issue of climate change has also brought the question related to the existence of preferred flow regimes up front in science media ( Palmer 1999 ; Corti et al. 1999 ; Hsu and Zwiers 2001

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Tiffany A. Shaw and Judith Perlwitz

1. Introduction During Northern Hemisphere (NH) winter, the stratosphere deviates significantly from radiative equilibrium because of the interaction of the stratospheric zonal-mean flow and planetary-scale waves, which propagate upward from the troposphere. The convergence of Eliassen–Palm (EP) flux by planetary-scale waves drives the equator-to-pole residual circulation that produces upwelling in the tropics and downwelling in high latitudes ( Dunkerton et al. 1981 ; McIntyre and Palmer 1983

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Christopher C. Chapman, Bernadette M. Sloyan, Terence J. O’Kane, and Matthew A. Chamberlain

). Since the time scales are considerably longer in the ocean than in the atmosphere, oceanic teleconnections can provide a mechanism for interseasonal and interannual predictions. Of particular interest are long baroclinic planetary waves (LPWs), which have the following characteristics ( Killworth et al. 1997 ; Killworth and Blundell 1999 ; Maharaj et al. 2007 ): wavelengths that are long relative to the local deformation radius R D ; periods that are long relative to the inertial period f −1 of

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Lawrence Coy, Stephen Eckermann, and Karl Hoppel

1. Introduction Sudden stratospheric warmings (SSWs) are a major component of the stratospheric circulation. Over the course of a few days the wintertime westerly stratospheric polar vortex is disrupted and the midstratospheric temperatures in the polar night increase rapidly by as much as 60 K (see Andrews et al. 1987 ). These dramatic changes are produced when strong planetary-scale Rossby wave forcing in the troposphere leads to Rossby wave breaking and dissipation in the stratosphere (see

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Sukyoung Lee, Steven Feldstein, David Pollard, and Tim White

reflectivity due to a reduction in the number of cloud condensation nuclei ( Kump and Pollard 2008 ). In this study, we propose and then test the mechanism that enhanced and localized tropical convection can also trigger high-latitude warming through the excitation of poleward-propagating planetary-scale Rossby waves, which transport heat poleward and induce sinking motions. Our proposed mechanism is based on the premise that under the high CO 2 loading conditions, tropical convection was more intense and

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Paul J. Roebber

; Anderson 1995 ; Luo and Chen 2006 ; Woollings et al. 2008 ; and many others). Additional research (e.g., Colucci 1987 , 2001 ) suggests that blocking onset may depend on the phasing between features on the planetary and synoptic scales. Colucci and Alberta (1996) further investigate the relationship between cyclogenesis and blocking and find some association between cyclone developments of various intensities and block onset but that the relationship is not sufficient to develop an empirical

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Junjun Liu and Tapio Schneider

that absolute vorticity is not mixed across the equator but separately by the Rossby wave lobes on either side of the equator. Fig . 10. Latitudinal absolute vorticity profiles. The blue line shows the planetary vorticity f = 2Ωsin ϕ ; the dashed magenta line shows the end state of homogenized absolute vorticity in each hemisphere; and the solid magenta line shows the absolute vorticity at 2 bar in the simulation with an intrinsic heat flux of 35.0 W m −2 , Δ s = 0.4, and no drag in the

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Elmar R. Reiter and Daniel Westhoff

732 JOURNAL OF THE ATMOSPHERIC SCIENCES VOLUME38 -A Planetary-Wave Climatology ELMAR R. REITER AND DANIEL WESTHOFFDepartment of Atmospheric Science, Colorado State University, Fort Collins 80523(Manuscript received 30 September 1980, in final form 23 December 1980)ABSTRACT Ultralong and long planetary waves are analyzed at the 500 mb level in terms of their amplitudes, phasesand

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