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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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Christopher G. Kruse and Ronald B. Smith

—that they move their energy through a fluid via pressure–velocity correlations. In unsheared flow, the group velocity describes the movement of the wave packet relative to the fluid. The vertical heat flux, , is another useful diagnostic. It can identify regions of thermal convection or regions where shear-induced turbulence in a stably stratified fluid is mixing heat downward . Small-amplitude gravity waves transport no heat . Other potentially useful quadratic quantities such as pseudomomentum

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Qingfang Jiang, James D. Doyle, Stephen D. Eckermann, and Bifford P. Williams

underlying terrain, and their sources are still not well understood. Possibilities include small-island terrain such as the South Georgia Island (e.g., Alexander et al. 2009 ; Alexander and Grimsdell 2013 ; Vosper 2015 ) and the Auckland Islands ( Eckermann et al. 2016 ), synoptic-scale instabilities associated with baroclinic storm systems ( Hendricks et al. 2014 ), and long downstream propagation of waves from terrain sources such as the Southern Andes ( Preusse et al. 2002 ; Shutts and Vosper 2011

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

waves launched by mountainous islands near 60°S (e.g., Alexander and Grimsdell 2013 ), neglected meridional propagation or focusing of GWs into the stratospheric polar vortex jet (e.g., Sato et al. 2009 ), or underrepresented nonorographic GWs and drag resulting from jet and frontal imbalances near 60°S (e.g., Jewtoukoff et al. 2015 ) in climate simulations. It is less clear if too little planetary wave drag is part of the cold-pole problem. However, Sigmond and Scinocca (2010) found that

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

troposphere, and Kiemle et al. (2007) made use of airborne DWL data in combination with water vapor measurements of a differential absorption lidar in order to estimate the latent heat flux in the boundary layer. Recently, Chouza et al. (2016) showed that vertical wind speed can be retrieved from airborne DWL measurements with a mean systematic uncertainty of 0.05 m s −1 and that the data are valuable for characterizing island-induced GWs. They also revealed that adequate corrections of horizontal

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Ronald B. Smith, Alison D. Nugent, Christopher G. Kruse, David C. Fritts, James D. Doyle, Steven D. Eckermann, Michael J. Taylor, Andreas Dörnbrack, M. Uddstrom, William Cooper, Pavel Romashkin, Jorgen Jensen, and Stuart Beaton

expressions, the symbols g , C p , θ , Ω, and ϕ are gravity, specific heat capacity, potential temperature, Earth rotation rate, and latitude, respectively. Gravity waves play a significant role in atmospheric dynamics by dispersing mesoscale horizontal potential temperature gradients, aiding geostrophic adjustment, and transporting energy and momentum from source to sink regions ( Eliassen and Palm 1960 ; Bretherton 1969 ; Holton 1982 ; Fritts and Nastrom 1992 ; Alexander et al. 2010 ). The

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Ronald B. Smith and Christopher G. Kruse

positive for these legs, indicating upward wave propagation. These EFz values were 5.0, 3.5, 3.6, 5.4, 5.3, 5.1, and 6.7 W m −2 for the seven 12.1-km legs and 3.1 and 1.7 W m −2 for the two 13.8-km legs. The reduction of EFz aloft is probably caused by nondissipative wave energy absorption in the negative shear above the jet stream core. Fig . 7. The South Island of New Zealand with the DEEPWAVE cross-mountain flight legs indicated. The box is the domain of variance integration for WRF Model output

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