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

theory ( Monin and Obukhov 1954 ). The stability functions for unstable and neutral conditions are based on Byun (1990) , and those for the free convection and stable case on Deardorff (1972) . ARPS is run in a one-way nesting mode. The outermost simulation domain (9-km grid spacing) is initialized from the National Oceanic and Atmospheric Administration’s (NOAA) 12-km North American Mesoscale (NAM) analysis dataset and is then successively nested down to grids of finer horizontal spacings (see

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Vanda Grubišić and Brian J. Billings

simulations a. Sierra Rotors Project: Field site and instrumentation Owens Valley is a nearly north–south-oriented rift valley located to the lee of the Sierra Nevada in eastern California ( Fig. 1a ). The Sierra Nevada forms the valley’s western boundary. Its eastern boundary is formed by two mountain ranges: the White Mountains to the north and the Inyo Mountains to the south connected at Westgard Pass east of Big Pine ( Fig. 1b ). The width of the valley is approximately 30 km from ridgetop to ridgetop

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Lukas Strauss, Stefano Serafin, and Vanda Grubišić

typical flow scenarios and possible transitions between them. Conclusions are drawn in section 5 . 2. The Terrain-Induced Rotor Experiment a. Geographical context Topographic maps of the Sierra Nevada and Owens Valley are shown in Fig. 2 . The Sierra Nevada stretches approximately 640 km from south-southeast to north-northwest and is about 110 km wide. Some of its peaks reach 4000 m MSL and more, the highest one being Mt. Whitney (4421 m MSL). Gentle westward and steep eastward slopes characterize

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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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Qingfang Jiang, Ming Liu, and James D. Doyle

largely controlled by near-surface meteorological conditions, namely wind speed and stability (therefore, surface friction velocity). In a recent study of the high wind climatology in Owens Valley, Zhong et al. (2008) found that strong winds (defined as hourly mean wind speed above 7 m s −1 ) observed by stations on the valley floor are primarily bidirectional, either up-valley (i.e., south-southeasterly) or, less frequently, down-valley (i.e., north-northwesterly). The well-known westerly downslope

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Bowen Zhou and Fotini Katopodes Chow

ISFF central tower (36.801 52°N, 118.160 02°W). Three one-way-nested domains ( Fig. 1a ) are used to zoom into the region of interest in both horizontal and vertical directions. The ratio of horizontal domain lengths between successive nests is 5 to 1. Simulations are first performed on a 2400-m horizontally spaced grid that covers the entire valley and the mountain ranges. Realistic initial and lateral boundary conditions are obtained from the North American Mesoscale (NAM) reanalysis dataset

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Christian Kühnlein, Andreas Dörnbrack, and Martin Weissmann

(eastern dot), and the position of upstream profiles ( Fig. 2 ) in the Central Valley, CA. (right) Vertical west–east sections along 36.8°N showing potential temperature θ (black lines, K) and horizontal wind magnitude (gray shading, m s −1 ). On 25 March 2006, a trough passed the west coast of North America and at 1800 UTC (1000 local time, which is Pacific standard time) the trough axis was located west of the Sierra Nevada. At the leading edge of the trough, and still in the warm sector before the

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Laurence Armi and Georg J. Mayr

-two-dimensional shape ( Fig. 1 ). The western slope of the Sierra Nevada rises gently to approximately 4 km MSL at its crest from where it drops steeply by almost 3 km into Owens Valley. At the valley floor, Owens Valley is approximately 15 km wide. At its eastern side lies another mountain range made up of the Inyos to the south and the higher Whites to the north, separated by the gap of Westgard Pass (2230 m MSL). The crest-to-crest distance across Owens Valley is almost 30 km. Fig . 1. (top) Overview map with

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Patrick A. Reinecke and Dale R. Durran

processes are represented in the COAMPS simulations, including the parameterization of the boundary layer, radiative transfer, and moist processes (see Hodur 1997 ). To resolve the multiscale aspect of downslope winds and mountain waves, three one-way interacting nests with 27-, 9-, and 3-km horizontal resolution are centered over the Sierra Nevada and Owens Valley ( Fig. 1 ). The outermost 27-km mesh encompasses the western North American continent as well as a large portion of the eastern Pacific

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Patrick A. Reinecke and Dale Durran

mountain-wave activity was forecast operationally during (intensive observing period) IOP-13 in the Terrain-Induced Rotor Experiment (TREX; Grubišić et al. 2008 ). To explicitly resolve the scales of motion associated with mountain waves, three one-way nests with increasing horizontal resolution are used. Figure 12a shows the location and topography on the three nests. The outermost domain has a horizontal resolution of 27 km and covers a large region of the western North American continent and

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