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Gabriel Wolf and Volkmar Wirth

: complex demodulation (e.g., Lee and Held 1993 ; Chang and Yu 1999 ) and the Hilbert transform ( Zimin et al. 2003 ). Commonly it is assumed that the perturbation has the form of an almost-plane wave, that is, C ( λ ) = cos( sλ ) and, hence, where s = s c is the wavenumber of the carrier wave. However, observed atmospheric Rossby wave packets deviate from the almost-plane wave paradigm to a certain extent. Troughs tend to be narrower than ridges, something well known to the experienced

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

rotation and the sphericity of Earth [for an introductory-level text on Rossby waves see Rhines (2002) ]. Rossby waves are in distinct contrast to other types of waves such as gravity waves or sound waves, which rely on gravity or the compressibility of air, respectively, for their basic restoring mechanism. The atmospheric general circulation cannot be understood without reference to Rossby waves because they transfer energy, moisture, and momentum across large distances. This can generate

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Andrea Schneidereit, Silke Schubert, Pavel Vargin, Frank Lunkeit, Xiuhua Zhu, Dieter H. W. Peters, and Klaus Fraedrich

train. As this wave train is apparent throughout the troposphere ( Orsolini and Nikulin 2006 ), the large-scale flow seems to play an important role in European heat waves. Model simulations indicate that the anomalous circulation during the summer of 2010 over eastern Europe can be ascribed primarily to natural internal atmospheric variability rather than to climate change or ocean boundary conditions like sea surface temperature or sea ice extent ( Dole et al. 2011 ), reflecting changes in the

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Lisa-Ann Quandt, Julia H. Keller, Olivia Martius, and Sarah C. Jones

1. Introduction As atmospheric blocking may cause high-impact weather like heat waves and flooding (e.g., Matsueda 2009 ), there is a special interest in its predictability and the physical processes that limit forecast quality. Blocking is a large-scale flow pattern that decelerates arriving eddies, as well as the background flow, and forces them to follow a more meridional direction (e.g., Rex 1950 ; Arakawa 1952 ; Sumner 1954 ). Atmospheric blocking is persistent and self-sustaining (e

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Franziska Teubler and Michael Riemer

1. Introduction Rossby waves are a fundamental ingredient of atmospheric dynamics. For synoptic-scale Rossby waves, the strong gradient of potential vorticity (PV) associated with the midlatitude jet effectively constitutes the waveguide ( Platzman 1949 ; Schwierz et al. 2004 ; Martius et al. 2010 ). A local perturbation of this waveguide may lead to the formation of distinct wave packets (e.g., Simmons and Hoskins 1979 ; Hakim 2003 ; Riemer et al. 2008 ). The significance of such Rossby

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Yannick Barton, Paraskevi Giannakaki, Harald von Waldow, Clément Chevalier, Stephan Pfahl, and Olivia Martius

IVT values. Fig . 6. Hovmöller plots of the meridional wind along the dynamical tropopause on the 325-K isentropic surface (shading, m s −1 ) for (a) 0000 UTC 12 Sep–1800 UTC 24 Oct 1993, (b) 0000 UTC 3 Nov–1800 UTC 6 Dec 2002, (c) 0000 UTC 10 Aug–1800 UTC 19 Aug 1965, and (d) 0000 UTC 10 Sep–1800 UTC 24 Oct 2000. Positive (negative) values indicate poleward (equatorward) flow. Stippling indicates atmospheric blocking averaged between 40° and 70° latitude. Green dashed lines show wave trains. The

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Gabriel Wolf and Volkmar Wirth

. Geophys. Res. Lett. , 41 , 2979 – 2987 , doi: 10.1002/2014GL059282 . 10.1002/2014GL059282 Grazzini , F. , and G. van der Grijn , 2002 : Central European floods during summer 2002. ECMWF Newsletter , No. 96, ECMWF, Reading, United Kingdom, 18–28. Grazzini , F. , and F. Vitart , 2015 : Atmospheric predictability and Rossby wave packets . Quart. J. Roy. Meteor. Soc. , 141 , 2793 – 2802 , doi: 10.1002/qj.2564 . 10.1002/qj.2564 Hoskins , B. J. , 1975 : The geostrophic momentum

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Andrea Schneidereit, Dieter H. W. Peters, Christian M. Grams, Julian F. Quinting, Julia H. Keller, Gabriel Wolf, Franziska Teubler, Michael Riemer, and Olivia Martius

( Tripathi et al. 2015 ). Matsuno (1971) developed a dynamical model of the stratospheric sudden warming phenomena in which tropospheric forced planetary wave packets propagate upward into the stratosphere. The deposition of their easterly angular momentum [Eliassen–Palm flux (EP flux) convergence] leads to a weakening and breakdown of the polar night jet. Several processes influence the occurrence of MSSW events in the Northern Hemisphere: the quasi-biennial oscillation (QBO) and the solar cycle (e

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Olivia Martius and Heini Wernli

1. Introduction Upper-level westerly jet streams are ubiquitous and important features of the subtropical atmospheric flow. On relatively short time scales (up to a few days) these jets serve as waveguides for synoptic-scale Rossby waves, which in turn can trigger high impact weather events (e.g., Martius et al. 2008 ; Feldstein and Dayan 2008 ). With regard to the transport of chemical constituents, the subtropical jets can act as local barriers for meridional exchange (e.g., Shuckburgh et

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Julia H. Keller, Sarah C. Jones, and Patrick A. Harr

and Lackmann 1995 ; Riemer et al. 2008 ; Scheck et al. 2011a ) the development of a midlatitude Rossby wave train. Hence, the impact of a transitioning TC on the midlatitude flow is not limited to the immediate vicinity of the cyclone itself. The triggered Rossby wave train may propagate far downstream, eventually enhancing the potential for downstream cyclogenesis on the opposite side of the ocean basin ( Agustí-Panareda et al. 2004 ; Harr and Dea 2009 ; Riemer and Jones 2010 ). The potential

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