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Ronald B. Smith, Bryan K. Woods, Jorgen Jensen, William A. Cooper, James D. Doyle, Qingfang Jiang, and Vanda Grubišić

properties of the tropopause may influence mountain waves propagating into the stratosphere. The sharp lapse rate and wind shear change at the tropopause may cause partial reflection and discontinuous aspects of wave structure. According to linear theory, the only wave properties that are likely to be continuous across the tropopause are the momentum flux (MF) and possibly the energy flux (EF; Eliassen and Palm 1961 , hereafter EP61 ). Once the waves have entered the stratosphere, the greater static

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Ronald B. Smith and Christopher G. Kruse

, hereinafter S16 ) provides an improved dataset for gravity wave spectral studies over mountains. All the standard physical variables (e.g., u , υ , w , p , and T ) were measured independently and redundantly. The Southern Alps of New Zealand are surrounded by ocean and are therefore compact. Spectral and physical analyses are easier if the disturbance is compact. The Southern Alps have rapid tectonic uplift and erosion rates ( Williams 1991 ) and one of the most rugged terrains in the world. Small

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James D. Doyle and Carolyn A. Reynolds

1. Introduction As stably stratified air flows over a topographic obstacle, gravity waves are generated and propagate away from the mountain. Vertically propagating mountain waves may amplify, overturn, and break, due to factors such as the decrease of atmospheric density with altitude, nonlinearity, and vertical gradients of the ambient winds and stability, all of which influence the wave amplitude. Wave breaking is thought to be a threshold phenomenon occurring when the wave grows beyond a

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Vanda Grubišić and Brian J. Billings

1. Introduction There are several mountain ranges worldwide that are well-known for generation of large-amplitude mountain waves. These include the Alps, the Andes, or the New Zealand Alps. In the United States, the most thoroughly documented range is the Colorado Front Range (e.g., Lilly and Zipser 1972 ; Clark et al. 2000 ). Another, the Sierra Nevada in California ( Fig. 1 ) has been until recently less well known among scientists, but it is equally well known among amateur and

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David M. Gaffin

elevations where stronger winds normally occur. It was ultimately determined that the cause of the high winds in the foothills was due to mountain waves that accelerated the winds in the foothills. While mountain-wave events that have produced extremely high winds have been well documented near the Rocky Mountains of the western United States (i.e., Blier 1998 ; Colle and Mass 1998a , b ; Colman and Dierking 1992 ; Durran 1990 ), these events remain largely undocumented near the southern Appalachians

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Qingfang Jiang and James D. Doyle

1. Introduction Moist processes have been largely ignored in the majority of mountain-wave studies, partially because of the complexity associated with moisture and microphysical processes. Studies of the interaction between moist airflow and mesoscale topography can be broadly classified into two categories. The first category includes quasi-analytical studies with highly simplified representations of moist processes. For example, a set of two-dimensional steady-state linear wave solutions

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Bryan K. Woods and Ronald B. Smith

1. Introduction While balloon soundings and remote sensing have contributed to mountain-wave observation, the most detailed observations derive from horizontal flight legs of research aircraft. Aircraft mountain-wave projects have been carried out in many regions of the world including the Alps, the Pyrenees, the Rockies, and the Sierra Nevada. The three major innovations in measurement technology in aid of these measurements were 1) gliders with a recording variometer, 2) aircraft with

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Thomas S. Lund, David C. Fritts, Kam Wan, Brian Laughman, and Han-Li Liu

1. Introduction Mountain waves (MWs) have been the subject of numerous observational, modeling, and theoretical studies over the previous 100 years ( Smith 2018 ). Examples of important physical effects include downslope winds, turbulence at flight altitudes, and transport and deposition of energy and momentum that have major roles in weather, climate, and atmospheric composition and structure. An extensive literature has addressed their dynamics and implications extending into the middle

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Maria-Vittoria Guarino, Miguel A. C. Teixeira, Teddie L. Keller, and Robert D. Sharman

1. Introduction Mountain waves, also known as orographic gravity waves, result from stably stratified airflow over orography. These waves can break at different altitudes and influence the atmosphere both locally, by generating, for example, aviation-scale turbulence ( Lilly 1978 ), and globally, by decelerating the general atmospheric circulation ( Lilly and Kennedy 1973 ). Several studies have investigated the role of mountain-wave activity in a wide range of atmospheric processes taking

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Stephen A. Cohn, Vanda Grubiššićć, and William O. J. Brown

lee waves and are associated with strong turbulence, wind shear, and variable and gusting surface winds (e.g., Grubiššićć and Billings 2007 ). Besides being a challenging fluid dynamics problem, they affect human activities as a hazard to both commercial and general aviation. They can also affect air quality by lofting and transporting aerosols and contaminants from the earth’’s surface ( Raloff 2001 ). This paper investigates characteristics of mountain waves, rotors, and rotor internal

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