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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

1. Introduction Over mountain areas the evolution of the boundary layer is particularly complex as a result of the interaction between boundary layer turbulence and thermally induced mesoscale wind systems, such as the slope and valley winds (e.g., Rotach et al. 2008 ). As the horizontal resolution of operational forecasts progresses to finer resolution, a larger spectrum of thermally induced wind systems can be explicitly resolved. It is therefore useful to document the current state

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Qingfang Jiang and James D. Doyle

fields. Lateral boundary conditions for the outermost grid mesh are derived from Navy Operational Global Analysis and Prediction System (NOGAPS) forecast fields. The computational domain contains four horizontally nested grid meshes of 91 × 91, 131 × 131, 157 × 157, and 256 × 256 grid points, and the corresponding horizontal grid spacings are 27, 9, 3, and 1 km, respectively. There are 55 levels in the vertical on a nonuniform sigma grid with finer spacing in the lower troposphere. The model top is

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Vanda Grubišić and Brian J. Billings

conditions were specified using the Naval Operational Global Atmospheric Prediction System (NOGAPS) forecast fields, which were applied every 6 h throughout all simulations. The simulation consisted of a 12-h spinup run initialized at 1200 UTC 23 March, and three subsequent 24-h runs initialized at 0000 UTC 24, 25, and 26 March. The initial fields for the 24-h runs were created by blending the previous COAMPS forecast with the NOGAPS analysis and available operational upper-air soundings and surface data

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Yanping Li, Ronald B. Smith, and Vanda Grubišić

Valley observations from the Terrain-Induced Rotor Experiment (T-REX) project. In section 4 we propose a novel approach for estimating the valley daily maximum mixed-layer depth using surface pressure and temperature amplitudes. Idealized 2D Weather Research and Forecasting Model (WRF) simulations are described in section 5 , together with a discussion of the physical processes involved in producing surface pressure and temperature variations in mountain valleys. Section 6 gives the results of

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Bowen Zhou and Fotini Katopodes Chow

numerical modeling over complex terrain: Operational applications. Mountain Meteorology: Bridging the Gap between Research and Forecasting, Springer, 591–653.

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Christian Kühnlein, Andreas Dörnbrack, and Martin Weissmann

, whereas the width of the valley is ~15 km. The next section briefly describes the overall meteorological evolution during IOP6. The Doppler lidar observations are presented in section 3 . Conclusions will be provided in section 4 . 2. Synoptic weather situation and upstream profiles The temporal evolution of the meteorological situation during IOP6 is depicted in Fig. 1 by means of 6-hourly European Centre for Medium-Range Weather Forecasts (ECMWF) analyses of geopotential height, wind, and

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James D. Doyle, Vanda Grubišić, William O. J. Brown, Stephan F. J. De Wekker, Andreas Dörnbrack, Qingfang Jiang, Shane D. Mayor, and Martin Weissmann

of the downslope wind speed and wave-breaking characteristics as diagnosed from idealized mesoscale ensemble forecasts (e.g., Doyle and Reynolds 2008 ). 6. Conclusions We have explored the dynamics and internal structure of mountain-wave-induced rotors during T-REX IOP 13 through the use of a suite of ground-based and airborne observing platforms and very high-resolution simulations using a large-eddy simulation version of the nonhydrostatic COAMPS model. The observations and model results

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Thomas Raab and Georg Mayr

would also have to be called rotor. To avoid misconceptions we have decided to use the more general term “horizontal vortex.” The aims of the study are to examine measurements along the surface from a weather station on wheels (WOW) and along vertical profiles on the upstream and downstream side from operational and research radiosondes to describe different settings for windstorms down the Sierra Nevada into Owens Valley (OV) in California during the Sierra Rotors Project (SRP; Grubišić and

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James D. Doyle and Dale R. Durran

low-level rotor, resulted in the loss of an engine on a commercial United Airline Boeing 747–100 at 600-m AGL near Anchorage, Alaska ( Kahn et al. 1997 ). In spite of their clear significance to the meteorology and aviation communities, the dynamics and structure of rotors are poorly understood and forecasted, in part because of infrequent and insufficient observational measurements, and inadequate sophistication and fidelity of numerical weather prediction models. Mountain waves and rotors were

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Ivana Stiperski and Vanda Grubišić

instability of steady mountain waves . J. Fluid Mech. , 568 , 303 – 327 . Louis , J. F. , 1979 : A parametric model of vertical eddy fluxes in the atmosphere . Bound.-Layer Meteor. , 17 , 187 – 202 . Louis , J. F. , M. Tiedtke , and J. F. Geleyn , 1982 : A short history of the operational PBL parameterization at ECMWF . Proc. Workshop on Planetary Boundary Layer Parameterization, Reading, United Kingdom, European Centre for Medium-Range Weather Forecasts, 59–79 . Mayr , G. J. , and A

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