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C. David Whiteman, Sebastian W. Hoch, and Gregory S. Poulos

radiation is thus seen as a proxy measurement of the surface radiating temperature during the period of temperature rise and fall, with the presence of the temperature rise and its subsequent fall indicated by a rise and fall of net radiation. A downward-directed sensible heat flux of 10–30 W m −2 occurred during the cooling period before the temperature rise. The warming episode is marked by the rapid increase in downward turbulent sensible heat flux triggered by an increased wind shear at the top of

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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

not include prognostic soil moisture; the latent heat flux is determined by multiplying potential evaporation with the moisture availability). It should be noted that the low initial value of atmospheric moisture and the very dry soil precluded the formation of any clouds (except for some radiatively insignificant clouds in MM5). b. Models The following models were used in the intercomparison study: the Advanced Regional Prediction System (ARPS; Xue et al. 2000 , 2001 ), the Consortium for Small

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

diurnal cycles in surface sensible heat fluxes. Along-valley and valley–plain temperature differences can be produced by at least three factors: radiative differences, differences in the conversion rate of net radiation to sensible heat flux, and by the valley volume effect ( Whiteman 2000 ). While the first two factors are attributed primarily to differences in land surface properties, they may also be influenced by the thermally induced flows themselves ( De Wekker et al. 1998 ). Much attention has

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Bowen Zhou and Fotini Katopodes Chow

conditions of strong winds and/or large cloud cover, which leads to reduced net radiative surface cooling ( Van de Wiel et al. 2003 ). On clear nights with weak winds, the SBL cools rapidly. Turbulent motions are strongly damped by buoyancy stratification. The SBL goes into a quiescent state, where turbulence is suppressed over prolonged periods greater than the time scale of the dominant eddies ( Nakamura and Mahrt 2005 ). In the intermittently turbulent SBL, energetic mixing events known as turbulent

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James D. Doyle and Dale R. Durran

equations expressed using tensor notation are where c p is the specific heat at constant pressure, R d is the dry gas constant, g is the acceleration due to gravity, ρ is the density, c is the speed of sound, ν is the hyperdiffusion coefficient, and f the Coriolis force. In this study, the Coriolis force is specified as 10 −4 s −1 . The overbar variables correspond to the reference state, which is horizontally homogeneous and in hydrostatic balance. The turbulent subgrid-scale fluxes for

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Vanda Grubišić and Brian J. Billings

(MISS; Cohn et al. 2004 ). Both systems contain a 915-MHz boundary layer radar wind profiler, a Radio Acoustic Soundings System (RASS), radiosonde launch capability, and an automated surface station that measures temperature, relative humidity, pressure, wind speed and direction, rainfall accumulation, and radiative fluxes. MAPR was positioned in the center of the valley near the southern line of AWS ( Fig. 1c ). Since MAPR contains multiple vertically pointing antennae, it can obtain a horizontal

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Laurence Armi and Georg J. Mayr

higher than at the valley station. Wind speeds decrease as gap overflow is undercut by air flowing down the slopes and down Owens Valley. The strong nocturnal radiative cooling in the valley finally provides an air mass that is colder than the synoptically advected air mass flowing through the gap. WOW data from around 2130 LST (0530 UTC) in Fig. 6c again resolve the spatial details of the flow near the surface. In the valley, flow has switched direction to northerly downvalley flow independent of

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

turbulence. A wide variety of in situ and remote sensors (both ground-based and airborne) was deployed in support of T-REX. In addition to the coherent Doppler lidars, other ground-based instrumentation included the NCAR Raman-Shifted Eye-safe Aerosol Lidar (REAL), thermosondes, sodar/RASS, flux towers, the NCAR Integrated Sounding System Multiple Antenna Profiler Radar, and HOBO weather stations (see Grubišić et al. 2004 for a more exhaustive list). Aircraft-based measurements were collected by the

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Patrick A. Reinecke and Dale Durran

well as potential temperature θ and Exner function π are marched forward in time with a split-time-level integration ( Klemp and Wilhelmson 1978 ). A full suite of physical processes are represented in the COAMPS simulations including the parameterization of the boundary layer, radiative transfer, and moist processes (see Hodur 1997 ). As with the linear Boussinesq system presented above, the model variables are staggered on a C grid. The metric terms are computed in an internally consistent

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