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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

DVAR) DA algorithm. Hogan et al. (2014) provide a detailed description of the key model and DA components. In common with other operational DA systems, the current operational NAVGEM has a rigid upper boundary at 0.04 hPa ( z ~ 70 km: Hogan et al. 2014 ). For the DEEPWAVE reanalysis, the forecast model was reconfigured from 60 to 74 levels (L74) with a new upper boundary at 6 × 10 −5 hPa ( z ~ 115 km), then augmented with a range of additional physical parameterizations needed to model the

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Ronald B. Smith and Christopher G. Kruse

the wave field sees this finescale terrain. Even if it did, those short-wavelength waves would be nonhydrostatic and carry little momentum flux ( Smith and Kruse 2017 ). 4. The WRF wave drag dataset for New Zealand a. Data quality The observational basis for the current study is a continuous full-physics WRF Model simulation of airflow over New Zealand, done for the DEEPWAVE project from June through August 2014. The mesoscale simulation was carried out with 6-km resolution with boundary

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

higher than 1 hPa were found to become unstable. Currently, we do not know why this is the case but will investigate this issue in the future. The initial and boundary conditions for the WRF Model are supplied by ECMWF operational analysis on 137 model levels with a temporal resolution of 6 h. Further details about the model setup can be found in the appendix . The complete WRF output is available every 60 and 30 min for the outer and inner domain, respectively. In addition, the momentary basic

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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

structured around a global, three-time-level (3TL), semi-implicit, semi-Lagrangian (SISL) dynamical core. In the vertical, the model uses the NEWHYB2 hybrid σ – p coordinate of Eckermann (2009) . For operational NWP at the Fleet Numerical Meteorology and Oceanography Center (FNMOC), 60 vertical layers (L60) are currently adopted with a rigid upper boundary at p top = 0.04 hPa (see Fig. 1 of Eckermann et al. 2014 ). As shown in Fig. 3b , in extending NAVGEM through the MLT, we mirrored those

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Christopher G. Kruse and Ronald B. Smith

. 1. Examples of (a) full pressure ( p ), (b) deplaned pressure ( ), (c) low-passed deplaned pressure ( ), and (d) high-passed deplaned pressure or perturbation pressure ( ) from a realistic 2-km WRF simulation. A cutoff length scale of L = 400 km was used. These analyses are valid at 1800 UTC 24 Jun 2014 at 4-km MSL. While edge artifact amplitude is reduced via deplaning, edge artifacts are not eliminated (e.g., Fig. 1d ). Edge artifacts decay away from the boundaries with a decay length scale

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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

current state of knowledge of gravity waves fluxes around the world is nicely reviewed by Geller at al. (2013) . They emphasize that satellites and global models are unable to resolve the short wavelength components of the gravity wave spectrum. In addition, wave parameterization schemes are oversimplified and differ from model to model. As a result, there are significant differences and uncertainties in regional wave momentum flux (MF) estimates. In the Southern Hemisphere winter, for example, the

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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

dynamics, and their significant dependence on GW sources and the environments through which they propagate, pose major challenges for their parameterizations in global weather and climate models. Scientific interests and societal needs have motivated many previous studies of GWs from the stable boundary layer and troposphere, through the stratosphere and mesosphere, and into the thermosphere. Among the more important of these are the following: GWs pose hazards to people and property; examples include

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

little to nearly half of tropopause-level tropical upwelling among model members. Surprisingly, despite variable GWD contributions, the circulation strength was found to be relatively constant, implying changes in planetary wave driving compensate variations in GW forcing (e.g., Cohen et al. 2013 ) and that the mean transport circulation alone may not strongly constrain GWD parameterizations. A current common problem in chemistry–climate models is that the Southern Hemisphere pole is too cold in the

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Stephen D. Eckermann, James D. Doyle, P. Alex Reinecke, Carolyn A. Reynolds, Ronald B. Smith, David C. Fritts, and Andreas Dörnbrack

is seeded by subwavelength instabilities that form at unstable wave phases ( Andreassen et al. 1998 ). Current weather and climate models typically run at horizontal gridpoint resolutions of ~10–100 km, approaching a so-called gray zone (e.g., Vosper et al. 2016 ) where long-wavelength gravity waves are resolved explicitly, but the net drag effects of smaller-scale waves on the resolved flow require parameterization ( Kim et al. 2003 ). Despite decades of research, vigorous debate persists about

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Christopher G. Kruse and Ronald B. Smith

use of periodic lateral boundary conditions, 2D flow, and no planetary vorticity . These idealizations limit the ambient flow response to MWD to deceleration, preventing MWD from being balanced by a pressure gradient or Coriolis force in a barrier jet–like response. The total (nondissipative plus dissipative) MW momentum deposition and ambient flow decelerations are trivially diagnosed in the MW–ambient flow coupled WRF solutions, as the model numerics time integrate the total momentum deposition

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