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John R. Albers and Thomas Birner

, our analysis will show that split and displacement SSWs indeed have very distinct prewarming evolutions. However, in contrast to Charlton and Polvani (2007) and Bancala et al. (2012) , who focused on planetary waves in the region below 30 km (10 hPa), we extend our analysis upward to 55 km (0.5 hPa) and analyze the combined effects of both planetary waves and gravity waves on vortex preconditioning and the resonant excitation theory of SSWs. In doing so, we focus particular attention on split

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Kevin M. Grise and David W. J. Thompson

climate, including the surface westerlies and the horizontal distribution of temperature. In the tropics, baroclinic instability is inhibited by weak rotation and small horizontal temperature gradients. Here, quasi-stationary equatorial planetary waves forced by the latent heat release from deep convection play a key role in the large-scale atmospheric circulation. Equatorial planetary waves are readily observed in the climatological-mean tropical circulation and are dominated by 1) an equatorially

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Kaoru Sato and Masahiro Nomoto

possible cause of the instability is planetary wave (PW) forcing (PWF) (e.g., Baldwin and Holton 1988 ; Geer et al. 2013 ). More recently, the role of gravity wave (GW) forcing (GWF) 1 in the formation of the unstable condition is also a subject of focus (e.g., McLandress and McFarlane 1993 ; Norton and Thuburn 1996 ; Watanabe et al. 2009 ; Ern et al. 2011 ). It is well known that GWF in the upper mesosphere is important as a driving force of the residual mean circulation from the summer

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Judith Berner and Grant Branstator

1. Introduction a. Background Nonlinearities in the internal dynamics of the atmosphere have the potential to influence the behavior of planetary waves in key respects. For example they can produce highly predictable states, and they can affect the way planetary waves react to external forcing ( Palmer 1999) . Although effects of nonlinearity are obvious in highly truncated models, as for example in the formation of multiple equilibria in Charney and DeVore’s (1979) model of planetary waves

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Oliver Watt-Meyer and Paul J. Kushner

, including a detailed comparison with previous approaches and an overview of the climatological wavenumber–frequency spectra in the extratropics. To investigate planetary wave interference effects, we will compare the structure of the standing waves and the climatological wave field. Last, we will compute the vertical and time-lagged coherences of the standing and traveling waves at selected Northern Hemisphere extratropical locations using correlation-coherence analysis ( Randel 1987 ). Section 4 will

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Chunhua Shi, Ting Xu, Dong Guo, and Zaitao Pan

1. Introduction A stratospheric sudden warming (SSW) is a typical manifestation of troposphere–stratosphere interaction in winter (e.g., Charney and Drazin 1961 ; Charlton and Polvani 2007 ). Since the first dynamical model of SSW was established by Matsuno (1971) , subsequent studies have suggested that the process of SSW is closely related to the upward propagation of planetary waves (PWs), especially waves 1 and 2, from the troposphere to the stratosphere (e.g., Nishii et al. 2011

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Gwendal Rivière, Loïc Robert, and Francis Codron

upper levels ( Rivière 2009 ). On the contrary, the planetary, low-frequency waves act to hasten the short-term decay of the zonal wind anomalies during the first week following their peak ( Feldstein and Lee 1998 ; Watterson 2002 ). By analyzing observational datasets, Lorenz and Hartmann (2003) showed that the jet acts as a waveguide for these waves; so they propagate into the jet and remove momentum from it. This general behavior of planetary waves is well reproduced in simple models ( O

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Tiffany A. Shaw

is eddy dominated, whereas during winter the flow is closer to angular momentum conserving. In a zonal-mean framework, the monsoon–anticyclone system can be considered as a planetary-scale Rossby wave driven by land–ocean (east–west) heating asymmetries [following Gill (1980) ] with associated planetary-scale wave transport. Lorenz (1969, 1984) made a clear distinction between the “ideal Hadley circulation,” which is zonally symmetric and the “modified Hadley circulation,” which includes east

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Cory Baggett and Sukyoung Lee

their ability to transport heat poleward. We find that the poleward sensible heat transport is 1.17 PW throughout the entire column—a value in good agreement with previous studies ( Peixoto and Oort 1992 ; Trenberth and Stepaniak 2003 ). Partitioning the transport between tropospheric (below 300 hPa) and stratospheric contributions, we find transports of 0.46 and 0.71 PW, respectively. Insomuch as there are mechanisms that excite transient planetary-scale waves that act to amplify through

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Lantao Sun, Walter A. Robinson, and Gang Chen

warming do not return to westerly until the final cooling takes place during the fall. The date on which the polar vortex breaks up, the so-called final warming onset time, varies from year to year. The interannual variability in the timing of the final warmings depends on the strength of planetary wave forcing ( Farrara and Mechoso 1986 ), and it can have a large impact on the chemical depletion of stratospheric ozone ( Salby and Callaghan 2007 ). A late final warming is often associated with more

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