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Stephan F. J. De Wekker and Shane D. Mayor

Abstract

First results are presented from the deployment of the NCAR Raman-Shifted Eye-Safe Aerosol Lidar (REAL) in the Owens Valley of California during the Terrain-Induced Rotor Experiment (T-REX) in March and April 2006. REAL operated in range–height indicator (RHI) and plan position indicator (PPI) scanning modes to observe the vertical and horizontal structures of the aerosol and cloud distribution in a broad valley in the lee of a tall mountain range. The scans produce two-dimensional cross sections that when animated produce time-lapse visualizations of the microscale and mesoscale atmospheric structures and dynamics. The 2-month dataset includes a wide variety of interesting atmospheric phenomena. When the synoptic-scale flow is strong and westerly, the lidar data reveal mountain-induced waves, hydraulic jumps, and rotorlike circulations that lift aerosols to altitudes of more than 2 km above the valley. Shear instabilities occasionally leading to breaking waves were observed in cloud and aerosol layers under high wind conditions. In quiescent conditions, the data show multiple aerosol layers, upslope flows, and drainage flows interacting with valley flows. The results demonstrate that a rapidly scanning, eye-safe, ground-based aerosol lidar can be used to observe important features of clear-air atmospheric flows and can contribute to an improved understanding of mountain-induced meteorological phenomena. The research community is encouraged to use the dataset in support of their observational analysis and modeling efforts.

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Gregory S. Poulos, Junhong Wang, Dean K. Lauritsen, and Harold L. Cole

), signal acquisition is not a concern where the cell signal grid is adequate. However, the retrieval of these sondes can be arduous and incomplete in complex terrain and does not allow for real-time access to data. The ability to access dropsonde data in real time is often a crucial component of scientific flight planning in modern-day field projects, particularly in the case of flight operations in hazardous or rapidly changing weather, such as during the recent Terrain-induced Rotor Experiment (T

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Georg J. Mayr and Laurence Armi

potential temperature step at the top of the colder valley air mass, the height of which changes throughout the day, primarily due to diurnal heating in the valley. Acknowledgments This study would not have been possible without the careful planning and flying of the University of Wyoming King Air operations group. As mission scientist, LA is particularly thankful for their willingness and ability to carry out these turbulent flights close to the eastern sierra slope. We thank Stephen Mobbs and Ralph

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

two-dimensional radial velocity measurements could be retrieved. ASU had previously collaborated with another lidar group during the Joint Urban 2003 Experiment (JU2003) to coscan a plan position indicator (PPI) plane and to retrieve vectors in the PPI plane (see Newsom et al. 2008 ). ASU and DLR anticipated that this could allow rotors and other smaller-scale vortical structures to be identified and characterized on a cross-barrier plane, providing results directly pertaining to the scientific

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

, 2008 : 2008 Owens Valley PM10 Planning Area Demonstration of Attainment State Implementation Plan January, 2008. Great Basin Unified Air Pollution Control District, 401 pp. [Available from Great Basin Unified Air Pollution Control District, 157 Short Street, Bishop, CA 93514.] . Stewart , J. Q. , C. D. Whiteman , W. J. Steenburgh , and X. Bian , 2002 : A climatological study of thermally driven wind systems of the U.S. Intermountain West. Bull. Amer. Meteor. Soc. , 83 , 699 – 708

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Laurence Armi and Georg J. Mayr

troposphere layer makes a transition from subcritical to supercritical flow. The difference is in the existence of a weak cap bounded by a stagnant isolating layer. The 18 February 1970 case ( Fig. 5c ) had no downslope windstorm at Boulder and no response in the supercritical flow in the troposphere layer aloft. Acknowledgments This study would not have been possible without the careful planning and flying of the University of Wyoming King Air operations group. As mission scientist, LA is particularly

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Qingfang Jiang and James D. Doyle

the momentum flux decreased rapidly with increasing altitude, and was substantially smaller in the upper troposphere. The maximum momentum flux convergence occurred just above the mountaintop level, indicating that most of the wave momentum flux was deposited into the lower troposphere through low-level wave breaking or hydraulic jumps. Shown in Figs. 9a,b are plan views of the zonal wind component and wind vectors at the surface valid at 1800 UTC 13 April (i.e., 1000 PST) and 0000 UTC 14 April

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Lukas Strauss, Stefano Serafin, and Vanda Grubišić

over 30 min (ISS2/MISS) and 5 min (MAPR). Finally, several scanning Doppler lidars were deployed. Here, data from the lidar operated by the Deutsche Zentrum für Luft- und Raumfahrt (DLR) ( Kühnlein et al. 2013 ) are used. Vertical-slice range–height indicator scans were performed at azimuthal angles of 50°, 80°, and 170° east of north (referred to as RHI-50, RHI-80, and RHI-170, respectively) to sample cross-valley and along-valley flows. Conical plan position indicator (PPI) scans were carried out

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Susanne Drechsel, Georg J. Mayr, Michel Chong, Martin Weissmann, Andreas Dörnbrack, and Ronald Calhoun

scanned either at fixed elevation and varying azimuth angles [plan position indicator (PPI), approximately 25%], or vice versa [range–height indicator (RHI), approximately 75%]. The range gates of the DLR lidar had a length of 105 m with the center of the first gate at 396 m, the range gates of the ASU lidar had a length of 85 m with the first gate at 441 m. With 100 range gates per beam, the absolute maximum range was 11 or 9 km, respectively, for the DLR and the ASU lidar (for more details see

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Laurence Armi and Georg J. Mayr

scientific friend Joachim Kuettner (1909–2011) who brought the two of us together and provided the organizational spark for T-REX. He also served as a role model for LA’s soaring and research flights. This study would not have been possible without the careful planning and flying of the University of Wyoming King Air operations group. As mission scientist, LA is particularly thankful for their willingness and ability to carry out these turbulent flights close to the eastern Sierra Nevada slope. We thank

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