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Roger M. Wakimoto and Hanne V. Murphey

along the boundary that experienced enhanced convergence owing to the surface flow. The results presented in this study suggest that it is not necessary for two boundaries to collide in order for thunderstorms to develop. Solenoidally generated horizontal circulations can produce conditions favorable for convection initiation even if the boundaries remain separate. The datasets collected on convergence boundaries during IHOP_2002 were the most comprehensive to date. In spite of the success of the

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Monica Górska, Jordi Vilà-Guerau de Arellano, Margaret A. LeMone, and Chiel C. van Heerwaarden

boundary layer developed as a typical well-mixed boundary layer, which grew steadily from 600 m at 1000 central standard time (CST) to 1100 m at 1400 CST. The meteorological conditions were characterized by clear skies and a steady southeast wind of 4 m s −1 . The aircraft (University of Wyoming King Air) flew above a site vegetated with mostly grass and with more winter wheat in the west—with soil moisture increasing eastward. Thus, some horizontal variability in the turbulent fluxes could be expected

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S. B. Trier, F. Chen, K. W. Manning, M. A. LeMone, and C. A. Davis

boundary conditions are obtained from National Centers for Environmental Prediction (NCEP) Environmental Data Assimilation System (EDAS) analyses. b. Simulations The importance of both land surface–atmosphere feedback processes and the initial land surface conditions on the daytime PBL evolution and precipitation during the 12-day period are determined from an analysis of four different simulations ( Table 1 ). The simulations employ LSMs of varying sophistication and initial land surface conditions of

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Robin L. Tanamachi, Wayne F. Feltz, and Ming Xue

boundary layer soundings at nearby airports as well as upper-air information at nonsynoptic times. Both the 9- and 3-km runs were initialized at 0600 UTC 12 June 2002, approximately 1 h prior to RDE A. The 9-km forecast was first run for 18 h (to 0000 UTC 13 June 2002), using the 6-h Eta forecasts from the 0000 UTC cycle as the boundary conditions. The 3-km run was initialized from the interpolated 9-km ADAS analysis and forced at the lateral boundaries by the 9-km ARPS forecasts. The 3-km forecast was

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Margaret A. LeMone, Fei Chen, Mukul Tewari, Jimy Dudhia, Bart Geerts, Qun Miao, Richard L. Coulter, and Robert L. Grossman

starting at 1200 UTC was conducted for the 4 days the aircraft flew ( Table 1 ), with the initial and boundary conditions from the National Centers for Environmental Prediction (NCEP) 6-hourly Eta Data Assimilation System (EDAS) on a 40-km grid. The physical parameterizations used include a bulk microphysics scheme based on Lin et al. (1983) , the Dudhia (1989) shortwave radiation scheme, the Rapid Radiative Transfer Model (RRTM) longwave parameterization scheme ( Mlawer et al. 1997 ), the

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F. Couvreux, F. Guichard, P. H. Austin, and F. Chen

, as lower boundary conditions, the surface fluxes, provided by HRLDAS and initial atmospheric profiles provided by MM5. This model predicts the development of the convective boundary layer from the early-morning profiles using time-varying surface fluxes. As noted in section 1 , mesoscale variability is not sensitive to horizontal structure below the 4-km convective length scale L Rau , which also matches the 4-km horizontal resolution of HRLDAS. Model columns are treated independently on the 1D

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Robert J. Conzemius and Evgeni Fedorovich

). Although the technical requirements of prescribing lateral boundary conditions for heterogeneous CBLs of this type made these goals too ambitious for the available computer power and LES numerical code, we hope to lay some groundwork and present some considerations for simulating heterogeneous CBLs of this type in the future. With this overall goal in mind, we aimed to adequately simulate the structure of the relatively shallow and homogeneous CBL east of the dryline, hoping to reproduce CBL turbulence

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Lindsay J. Bennett, Tammy M. Weckwerth, Alan M. Blyth, Bart Geerts, Qun Miao, and Yvette P. Richardson

structure of the boundary layer over land during synoptic-scale high pressure conditions has a well-defined diurnal evolution and has been described in terms of the vertical profile of virtual potential temperature θ υ ( Stull 1988 ) ( Fig. 1 ). During the early morning, the stable nocturnal boundary layer (NBL), characterized by an increase of θ υ with height, occupies the lowest few hundred meters and is overlaid by a neutrally stratified residual layer ( Fig. 1a ). Shortly after sunrise thermals

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Diane Strassberg, Margaret A. LeMone, Thomas T. Warner, and Joseph G. Alfieri

1. Introduction Numerous studies show that daytime fair-weather surface wind speeds predicted by numerical weather prediction (NWP) models tend to be slower than observed wind speeds. Applying five different planetary boundary layer (PBL) schemes in the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) to simulate the diurnal cycle of wind and temperature under weakly forced fair-weather conditions, Zhang and Zheng (2004

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Margaret A. LeMone, Fei Chen, Mukul Tewari, Jimy Dudhia, Bart Geerts, Qun Miao, Richard L. Coulter, and Robert L. Grossman

1 km AGL (lowest level 28 m AGL) in order to have finer resolution in the CBL. The horizontal grid spacing (number of points) of the three outer domains are 9 km (237 × 201), 3 km (280 × 229), and 1 km (391 × 289), respectively. Initial and boundary conditions are from the National Centers for Environmental Prediction (NCEP) 6-hourly Eta Data Assimilation System (EDAS) on a 40-km grid. In the control ARW-WRF simulation, the Noah LSM is initialized by volumetric soil moisture and temperature

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