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Stephen D. Eckermann, Dave Broutman, Jun Ma, James D. Doyle, Pierre-Dominique Pautet, Michael J. Taylor, Katrina Bossert, Bifford P. Williams, David C. Fritts, and Ronald B. Smith

). Fritts et al. (2016) review the planning, execution, and initial results of DEEPWAVE. One of the many scientific objectives of DEEPWAVE was to acquire gravity wave observations to test recent ideas that gravity waves generated by small island terrain in the Southern Ocean significantly influence the large-scale momentum budget of the middle atmosphere in austral winter. This idea first arose when Alexander et al. (2009) analyzed radiances acquired by the Atmospheric Infrared Sounder (AIRS) on the

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Stephen D. Eckermann, Jun Ma, Karl W. Hoppel, David D. Kuhl, Douglas R. Allen, James A. Doyle, Kevin C. Viner, Benjamin C. Ruston, Nancy L. Baker, Steven D. Swadley, Timothy R. Whitcomb, Carolyn A. Reynolds, Liang Xu, N. Kaifler, B. Kaifler, Iain M. Reid, Damian J. Murphy, and Peter T. Love

Wave Experiment (DEEPWAVE): An airborne and ground-based exploration of gravity wave propagation and effects from their sources throughout the lower and middle atmosphere . Bull. Amer. Meteor. Soc. , 97 , 425 – 453 , https://doi.org/10.1175/BAMS-D-14-00269.1 . 10.1175/BAMS-D-14-00269.1 Fritts , D. C. , and Coauthors , 2018 : Large-amplitude mountain waves in the mesosphere accompanying weak cross-mountain flow during DEEPWAVE research flight RF22 . J. Geophys. Res. , in press . 10

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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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Christopher G. Kruse and Ronald B. Smith

Kruse 2017 ). While MW spectra become increasingly narrow after a forcing period, they are shifted to longer scales with larger contributions to and variance. Because of the slow vertical propagation of these longer scales, it can take days for nondissipating MWs to depart the middle atmosphere and allow the ambient flow to recover, especially in cases with weak winds in the middle atmosphere. In cases with MW breaking, can be substantial. For example, in the zero- and negative-shear cases

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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

, such as those that often accompany large radar and/or rocket facilities, have made especially valuable contributions to GW studies. This is because no single instrument can define all of the atmospheric properties and spatial and temporal variability needed to fully quantify the local GW field. Examples of these facilities include the Arctic Lidar Observatory for Middle Atmosphere Research in Norway (69.3°N); the Poker Flat Research Range in Alaska (65.1°N); the Bear Lake Observatory in Utah (42°N

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

1. Introduction During the last decades, internal gravity waves have been studied intensely because of their importance for the circulation and structure of the middle atmosphere ( Fritts and Alexander 2003 ). The most energetic part of the gravity wave spectrum is excited in the troposphere, with prominent source mechanisms being the flow over topography (e.g., Smith et al. 2008 ), convection (e.g., Vadas et al. 2012 ), flow deformation, and vertical shear at upper-level fronts ( Plougonven

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Benjamin Witschas, Stephan Rahm, Andreas Dörnbrack, Johannes Wagner, and Markus Rapp

1. Introduction Internal waves are waves that oscillate within a stratified fluid. If the fluid is considered to be the atmosphere and the restoring force of vertical displaced air parcels is provided by buoyancy, such waves are called internal gravity waves or just gravity waves (GWs). GWs are ubiquitous in the atmosphere and their impact on the vertical transport and exchange of energy and momentum between the troposphere and the middle atmosphere is well known ( Fritts and Alexander 2003

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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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Christopher G. Kruse and Ronald B. Smith

1. Introduction Gravity waves are atmospheric buoyancy oscillations that transport energy and horizontal momentum vertically throughout the atmosphere ( McLandress 1998 ). The vertical propagation and dissipation of gravity waves are important as the carried energy and momentum are deposited wherever these waves break, affecting the mean flow. Gravity waves and their dissipation have long been recognized to be important in middle atmosphere dynamics ( Fritts 1989 ). Important gravity wave

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Christopher G. Kruse, Ronald B. Smith, and Stephen D. Eckermann

stratosphere and middle atmosphere over New Zealand, but does a valve layer exist elsewhere? Zonal-averaged, time-averaged zonal winds and parameterized total (orographic plus nonorographic) zonal GWD within MERRA are shown in Fig. 14a . The averaging period is June and July over the years 2011–15. Between 15° and 50°S and between 15- and 25-km altitude, there is a maximum in zonal GWD associated with a wind minimum above the subtropical jet. This GWD maximum is primarily due to the orographic GWD

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