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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

. REFERENCES Alexander , M. J. , and L. Pfister , 1995 : Gravity wave momentum flux in the lower stratosphere over convection . Geophys. Res. Lett. , 22 , 2029 – 2032 , doi: 10.1029/95GL01984 . Alexander , M. J. , and A. W. Grimsdell , 2013 : Seasonal cycle of orographic gravity wave occurrence above small islands in the Southern Hemisphere: Implications for effects on the general circulation . J. Geophys. Res. Atmos. , 118 , 11 589 – 11 599 , doi: 10.1002/2013JD020526 . Alexander , M. J

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Ronald B. Smith and Christopher G. Kruse

smoothing and (b) smoothed with L = 10 km. The effect of smoothing is to spread out the terrain onto the sea, decreasing the mountain peaks and filling in the valleys. The terrain volume in (2) is unchanged by smoothing. Other effects of Gaussian smoothing are given in Table 1 . Generally, smoothing has little impact on the terrain orientation ( and ). The smoothing decreases the large-scale anisotropy as the smoothing kernel [ (14) or (16) ] is isotropic. With very strong smoothing, the

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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

. J. , and A. W. Grimsdell , 2013 : Seasonal cycle of orographic gravity wave occurrence above small islands in the Southern Hemisphere: Implications for effects on the general circulation . J. Geophys. Res. Atmos. , 118 , 11 589 – 11 599 , doi: 10.1002/2013JD020526 . Alexander , M. J. , S. D. Eckermann , D. Broutman , and J. Ma , 2009 : Momentum flux estimates for South Georgia Island mountain waves in the stratosphere observed via satellite . Geophys. Res. Lett. , 36 , L

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Ronald B. Smith and Christopher G. Kruse

stagnating the flow, by overturning the flow, or by shear instability. The volume mode will increase its u -power dominance even further when we consider nonhydrostatic effects in the next section. Similar to (15) , the variance of vertical velocity from (3) and (A4) has volume and roughness components: With and , the ratio of the second to the first term in the curly braces in (16) is , so the roughness mode dominates the w power ( Fig. 2d ). To illustrate the relationship between

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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

trend of the seasonal warming in the stratosphere from June to August that is less pronounced in the MLS data. The differences in the vertical profiles might occur as a result of the much lower temporal and horizontal resolution of MLS compared to ERA-Interim. Small-scale effects like GWs are likely not well represented in the MLS measurements since the temporal resolution is 1 day at one place. The zonal wind profiles show the characteristic properties with a tropopause jet of U MAX ≈ 30 m s −1

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

these deep ( z ≊ 0–45 km) simulations. Using the smoother 5-arc-min DEM largely removed the spurious Π anomalies. Unfortunately, this reduced the model terrain heights and removed an important part of the terrain spectrum. However, stratospheric momentum fluxes and zonal GWD were nearly unaffected. REFERENCES Alexander , M. J. , and A. W. Grimsdell , 2013 : Seasonal cycle of orographic gravity wave occurrence above small islands in the Southern Hemisphere: Implications for effects on the

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

A. W. Grimsdell , 2013 : Seasonal cycle of orographic gravity wave occurrence above small islands in the Southern Hemisphere: Implications for effects on the general circulation . J. Geophys. Res. Atmos. , 118 , 11 589 – 11 599 , https://doi.org/10.1002/2013JD020526 . 10.1002/2013JD020526 Alexander , M. J. , S. D. Eckermann , D. Broutman , and J. Ma , 2009 : Momentum flux estimates for South Georgia Island mountain waves in the stratosphere observed via satellite . Geophys

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

calculating the wavelet coefficients. The cone of influence (COI) is the region of the wavelet spectrum where edge effects become important. Outside the COI, the spectral amplitude could be reduced because of the zero padding ( Torrence and Compo 1998 ). The absolute values of the individual spectra are averaged over a given time period to retrieve the mean spectrum for an observational period. Dominant vertical wavelengths are derived by examining the local maxima in the global mean wavelet spectrum

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

June and are kept constant throughout each simulation, covering 48 h. In the 2D WRF Model, open boundary conditions are used in flow direction. Note that horizontal winds are projected to a wind direction of 300° ( ), which is the direction of the Mt-A-2b transect ( Fig. 1 ). All idealized simulations are run without moisture and radiation effects. From both the WRF and the in situ flight-level data, vertical energy and momentum fluxes are calculated according to the method of Smith et al. (2008

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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

profiles were averaged over the years 2005–12 for v1.07 SABER, 2005–14 for v2.0 SABER and v2 and v3 MLS, and 2005–15 for v2.0 SABER and v4 MLS. Global-mean biases are plotted in Fig. 5 , showing a reproducible mean bias profile over all MLS and SABER retrieval versions. Consistent with previous studies (e.g., Schwartz et al. 2008 ), we found little seasonal or latitudinal variation in this bias. Note in particular from Fig. 5 the large increases in coincidence data with v2.0 SABER, due to higher

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