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James D. Doyle, Saša Gaberšek, Qingfang Jiang, Ligia Bernardet, John M. Brown, Andreas Dörnbrack, Elmar Filaus, Vanda Grubišić, Daniel J. Kirshbaum, Oswald Knoth, Steven Koch, Juerg Schmidli, Ivana Stiperski, Simon Vosper, and Shiyuan Zhong

near the surface to a constant of 200 m, which extends from an altitude of 800 m to at least 26 km (134 or more vertical levels). The fine vertical grid increment in the lowest 800 m of the model is used to better resolve the near-surface processes, particularly for the simulations performed with surface friction. The attributes of the 11 numerical models that are used in this intercomparison study are summarized in Table 1 . The numerical model suite includes: the Advanced Regional Prediction

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Juerg Schmidli, Gregory S. Poulos, Megan H. Daniels, and Fotini K. Chow

surface–atmosphere exchanges over mountainous regions are closely linked to slope and valley flows; and the effects of these flows on mesoscale fluxes need to be parameterized in numerical weather prediction and climate models (e.g., Noppel and Fiedler 2002 ; Weigel et al. 2007 ; Rotach and Zardi 2007 ). Three major mechanisms that can produce within-valley winds are thermal forcing, pressure-driven channeling, and downward momentum transport ( Whiteman and Doran 1993 ). Thermal forcing refers to

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Shiyuan Zhong, Ju Li, C. David Whiteman, Xindi Bian, and Wenqing Yao

provided substantial details on the spatial and temporal structure of waves/rotors. However, they were limited by their short duration and were therefore unable to provide enough information on the seasonal variation in windstorm frequency to gain a more complete understanding of high wind events. In this study, we combine long-term climate data from a line of weather stations along the axis of the Owens Valley with data from the North American Regional Reanalysis (NARR) to understand the general

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Juerg Schmidli, Brian Billings, Fotini K. Chow, Stephan F. J. de Wekker, James Doyle, Vanda Grubišić, Teddy Holt, Qiangfang Jiang, Katherine A. Lundquist, Peter Sheridan, Simon Vosper, C. David Whiteman, Andrzej A. Wyszogrodzki, and Günther Zängl

eliminate lateral boundary effects, which were found to significantly influence simulation results in previous model intercomparison studies ( Doyle et al. 2000 ; Thunis et al. 2003 ). This intercomparison project was conducted as part of the Terrain-Induced Rotor Experiment (T-REX), which took place in Owens Valley, California, in March–April 2006 ( Grubisic et al. 2008 ). The field campaign was complemented by several modeling efforts. 2. Experimental design a. Setup The intercomparison is based on

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Patrick A. Reinecke and Dale Durran

is that k̃ = k̃ 1 . Finally, Ñ and f̃ are associated with the averaging operators in (1) – (4) and are defined by respectively. Note the similarity between the semidiscrete dispersion relationship in (9) and the continuous dispersion relationship: In the limit of good horizontal and vertical resolution k̃ p → k , k̃ p → k , l̃ → l , Ñ → N , and f̃ → f , implying that ω → ω c . b. Flow over topography To investigate the effects of numerical errors in the discretized

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Bowen Zhou and Fotini Katopodes Chow

-propagating gravity waves ( Sun et al. 2004 ), turbulence and mean shear interactions ( Nakamura and Mahrt 2005 ), and slope and valley flow transitions ( WHP09 ). Note that except for the last reference, all mechanisms are derived from the Cooperative Atmospheric-Surface Exchange Study -1999 (CASES-99) over nearly flat terrain. In reality, SBL flows are usually affected by the complex land surface. Large-scale topographic features such as mountains and valleys have pronounced effects in stratified flows ( Baines

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James D. Doyle, Qingfang Jiang, Ronald B. Smith, and Vanda Grubišić

flow response is governed by ĥ and the mountain Rossby number, Ro = U / fL , where f is the Coriolis parameter and L is the mountain half-width (e.g., Gill 1982 ; Pierrehumbert and Wyman 1985 ; Thorsteinsson 1988 ). For large Ro (>10), rotational effects are weak and the response is primarily governed by vertically propagating gravity waves ( Gill 1982 ). Inertia–gravity waves dominate when Ro ∼ 1, which are characterized by quasi-horizontal energy propagation and relatively small

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Vanda Grubišić and Brian J. Billings

. In addition to the baseline run, we have conducted additional experiments in order to investigate sensitivity of our numerical results to the effects of radiational heating as well as downstream topography. In the sensitivity run for radiation, the radiation scheme was applied every 15 min, compared to every 60 min in the baseline run. In the sensitivity run for downstream topography, the White and Mountains were replaced in all model domains with flat terrain, matching the height of the lowest

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Michael Hill, Ron Calhoun, H. J. S. Fernando, Andreas Wieser, Andreas Dörnbrack, Martin Weissmann, Georg Mayr, and Robert Newsom

effects of strong winds on aircraft in the area near Colorado Springs in 1997. Darby and Poulos (2006) compared lidar measurements from MCAT with numerical models (horizontal wind components; theoretical versus measured results) during periods of lee wave and rotor interaction. However, it has been difficult to characterize rotors in sufficient detail to relate descriptions of intense, instantaneous turbulence (encountered by aircraft) with mean results from low-resolution numerical models. As

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Stefano Serafin, Lukas Strauss, and Vanda Grubišić

through 900-MHz spread-spectrum wireless radios. Fig . 2. View of station 3, looking toward the west and showing the gently sloping alluvial fan and the steep eastern sierra slopes. The photograph is by G. McCurdy (Western Regional Climate Center). In this study, we use 5 yr of 30-s data from the time interval between 29 February 2004 and 28 February 2009. Data availability during this period is generally very good, but it deteriorates in 2009–13. Before 2009, the fraction of missing data remains

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