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Mozhgan Amiramjadi, Ali R. Mohebalhojeh, Mohammad Mirzaei, Christoph Zülicke, and Riwal Plougonven

are orography, convection, and coupled jet and front systems (e.g., Plougonven and Zhang 2014 ), which are mainly located in the troposphere. Based on their sources, the IGWs are thus classified into “orographic” and “nonorographic” (e.g., Kim et al. 2003 ) and dealt with separately in IGW parameterization schemes as they have distinct characteristics and impacts ( McLandress et al. 2013 ). Through their sources, the nonorographic IGWs are connected to the large-scale flow which is dominantly

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Sonja Gisinger, Andreas Dörnbrack, Vivien Matthias, James D. Doyle, Stephen D. Eckermann, Benedikt Ehard, Lars Hoffmann, Bernd Kaifler, Christopher G. Kruse, and Markus Rapp

tropospheric jet streams generate vertically propagating gravity waves in the troposphere and lower stratosphere ( Smith 1979 ; Gill 1982 ; Baines 1995 ; Fritts and Alexander 2003 ; Nappo 2012 ; Sutherland 2010 ; Plougonven and Zhang 2014 ). Through their far-field interactions, gravity waves constitute an important coupling mechanism in Earth’s atmosphere. The associated redistribution of momentum and energy controls the global middle-atmospheric circulation ( Dunkerton 1978 ; Lindzen 1981 ). To

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David C. Fritts, Ronald B. Smith, Michael J. Taylor, James D. Doyle, Stephen D. Eckermann, Andreas Dörnbrack, Markus Rapp, Bifford P. Williams, P.-Dominique Pautet, Katrina Bossert, Neal R. Criddle, Carolyn A. Reynolds, P. Alex Reinecke, Michael Uddstrom, Michael J. Revell, Richard Turner, Bernd Kaifler, Johannes S. Wagner, Tyler Mixa, Christopher G. Kruse, Alison D. Nugent, Campbell D. Watson, Sonja Gisinger, Steven M. Smith, Ruth S. Lieberman, Brian Laughman, James J. Moore, William O. Brown, Julie A. Haggerty, Alison Rockwell, Gregory J. Stossmeister, Steven F. Williams, Gonzalo Hernandez, Damian J. Murphy, Andrew R. Klekociuk, Iain M. Reid, and Jun Ma

= flight level, SI = South Island, CW = convective waves, FWs = frontal waves, SO = Southern Ocean. IOPs are shown in the context of the large-scale ECMWF horizontal winds from 0 to 80 km in Fig. 4 (top). The dominant feature is the polar night jet with a maximum wind often exceeding 100 m s −1 at ∼50–60 km that is presumably modulated in strength by PWs on time scales of ∼5–10 days. The poleward jet associated with frontal systems exhibits episodic maxima of ∼30–50 m s −1 at ∼8–12 km on similar

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Mahnoosh Haghighatnasab, Mohammad Mirzaei, Ali R. Mohebalhojeh, Christoph Zülicke, and Riwal Plougonven

Alexander 2003 ) over long distances and interacting with other phenomena through, for example, triggering convection. Previous observational and numerical studies have shown several sources for IGWs as orography, convection, shear instability, jet streams, and fronts (e.g., Uccellini and Koch 1987 ; Eckermann and Vincent 1993 ; O’Sullivan and Dunkerton 1995 ; Guest et al. 2000 ; Plougonven and Snyder 2007 ). The IGWs affect the atmospheric general circulation through breaking and dissipation by

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Mohammad Mirzaei, Ali R. Mohebalhojeh, Christoph Zülicke, and Riwal Plougonven

wave polarization relations. Previously, the HDA has been applied by Zülicke and Peters (2008) and Mirzaei et al. (2014) for the validation of a bulk parameterization of IGWs generated by jets, fronts, and convection. As its name suggests, the HDA’s working rests on certain assumptions on the wave field like the presence of a locally dominant wavenumber and sufficient separation with the large-scale balanced flow. By construction, the HDA performs well in regions of space filled by the coherent

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Martina Bramberger, Andreas Dörnbrack, Henrike Wilms, Steffen Gemsa, Kevin Raynor, and Robert Sharman

-air turbulence (CAT). Well-known generation processes of turbulence affecting aircraft at cruising altitudes comprise thunderstorms, strong wind shears related to upper-level fronts and jet streams, unbalanced flow, and breaking mountain waves (e.g., Vinnichenko et al. 1980 ; Lester 1993 ; Wolff and Sharman 2008 ; Lane et al. 2012 ; Sharman et al. 2012b ). Considering the generation process, turbulence directly related to breaking mountain waves is referred to as mountain wave turbulence (MWT) ( Sharman

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Gergely Bölöni, Bruno Ribstein, Jewgenija Muraschko, Christine Sgoff, Junhong Wei, and Ulrich Achatz

resulting in a constant buoyancy frequency . This implies a reference density profile where is the density scale height. Some of the test cases involve a prescribed background jet as an initial mean flow with a half-cosine wave shape: where is the maximal magnitude of the jet initialized at height , and is the width (i.e., vertical extent) of the half-cosine shape. In these cases, the wave-induced mean flow is diagnosed as : that is, the initial mean wind is subtracted from the total mean wind

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Tanja C. Portele, Andreas Dörnbrack, Johannes S. Wagner, Sonja Gisinger, Benedikt Ehard, Pierre-Dominique Pautet, and Markus Rapp

-based lidar observations in the lee of New Zealand’s Alps during DEEPWAVE revealed enhanced gravity wave activity in the stratosphere and mesosphere, which lasted about 1–3 days and alternated with quiescent periods ( Kaifler et al. 2015 ). The gravity wave forcing due to passing weather systems, the appearance of tropopause jets, and the middle atmosphere wave response were all observed with a similar frequency and duration of 2–4 days ( Fritts et al. 2016 ; Gisinger et al. 2017 ). The episodic nature

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Claudia Christine Stephan, Cornelia Strube, Daniel Klocke, Manfred Ern, Lars Hoffmann, Peter Preusse, and Hauke Schmidt

on troposphere–stratosphere exchanges of water vapor, ozone, and other gases ( Baldwin et al. 2001 ), as well as remote effects on global circulation. Deep convective systems are a major source for GWs in the tropics and the summer midlatitudes ( Pfister et al. 1993 ; McLandress et al. 2000 ; Preusse et al. 2001 ; Hoffmann and Alexander 2010 ; Choi et al. 2012 ). Other important tropospheric GW sources are regions of imbalanced flow near jets (e.g., O’Sullivan and Dunkerton 1995 ; Zhang

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Benedikt Ehard, Peggy Achtert, Andreas Dörnbrack, Sonja Gisinger, Jörg Gumbel, Mikhail Khaplanov, Markus Rapp, and Johannes Wagner

was often aligned with the evolving polar night jet. This flow constellation is known to excite mountain waves and to facilitate their vertical propagation into the lower and middle stratosphere (e.g., Dörnbrack et al. 2001 ). Figure 2 presents the temporal evolution of temperature and wind above Esrange for the period from 21 November to 15 December 2013. The atmospheric parameters are taken from 6-hourly operational analyses of the IFS. The vertical temperature distribution shows a cold

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