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Margaret A. LeMone, Mukul Tewari, Fei Chen, Joseph G. Alfieri, and Dev Niyogi

; Chen and Dudhia 2001b ; Ek et al. 2003 ) for both warm and cold seasons. Chen et al. (2001a) demonstrated that replacing a “bucket model” with the Noah LSM improved 24–48-h precipitation forecasts in the National Centers for Environmental Prediction (NCEP) Eta Model as much as doubling the model horizontal resolution. Today, Noah is used in operational NWP models at NCEP and the U.S. Air Force Weather Agency. In the first two papers of this series, we used data for the moist grasslands and

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John R. Mecikalski, Kristopher M. Bedka, Simon J. Paech, and Leslie A. Litten

( Table 2 ), and possess environments in which moisture for CI was not a factor limiting cumulus growth and rainfall. The 6 and 12 July, and 28 August 2004 CI events were also selected as the synoptic-scale forcing was relatively weak, storm motions were relatively slow (≤15 m s −1 ), and both cloud and storm motions were generally uniform along one velocity vector regardless of cloud size (i.e., cumuli in both pre- to post-CI state). Weak vertical shear and the lack of a deep dry layer within the

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Robert J. Conzemius and Evgeni Fedorovich

, the buoyancy flux increases, allowing the CBL growth to maintain a nearly constant rate. Near the end of the simulation, as surface buoyancy flux diminishes, the shear becomes strong and the stratification becomes weaker, allowing the CBL to continue growing steadily. All of these changes in forcing for CBL development cause its growth to deviate substantially from the t 1/2 relationship described for shear-free CBLs growing in constant stratification ( Fedorovich et al. 2004a ). See Fedorovich

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

the evolution of an observed BL with mesoscale variability using a collection of 1D models. The BL models are initialized with heterogeneous atmospheric fields provided by a mesoscale model and with surface fluxes calculated by a soil–vegetation–atmosphere transfer (SVAT) model. This framework allows separating the effect of heterogeneity of surface forcing and early-morning atmospheric conditions, permitting a direct comparison of their respective impacts on the development and maintenance of

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

observations of sensible and latent heat fluxes at one surface station (station 7) along the aircraft track. Argonne National Laboratory operated another surface flux site close to the track, a grass site at Smileyberg, Kansas, which measured CO 2 fluxes ( Coulter et al. 2006 ). These measurements from station 7 and the Smileyberg site are used for comparison with the surface fluxes in the analysis of the single-value method and as an input surface forcing in the numerical experiments ( Fig. 2 ). b. Large

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John H. Marsham, Stanley B. Trier, Tammy M. Weckwerth, and James W. Wilson

impacts of low-level stability on the strength of surface cold pools and their associated winds. 5. Summary and discussion Nocturnal convection is difficult to forecast accurately. Compared with surface-based convection, orography, and other easily detected forcing features such as boundary layer convergence lines play a less prominent role in initiating elevated convection. Elevated initiation is instead often controlled by elevated features such as low-level jets and waves, with

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

anomalies specific to the 1993 warm season could not account for the precipitation anomaly, but, similar to Beljaars et al. (1996) , they concluded that heavier precipitation was promoted by wetter soil upstream. In contrast, Paegle et al. (1996) found a negative feedback between precipitation and upstream soil wetness for July 1993. They concluded that drier soil upstream resulted in stronger PBL forcing of the nocturnal low-level jet (LLJ), which led to enhanced convergence and water vapor

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

IHOP_2002 aircraft and surface data. Mon. Wea. Rev. , 136 , 964 – 972 . Sun , W-Y. , and Y. Ogura , 1979 : Boundary-layer forcing as a possible trigger to a squall-line formation. J. Atmos. Sci. , 36 , 235 – 254 . Taylor , C. M. , D. J. Parker , and

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Roger M. Wakimoto and Hanne V. Murphey

1. Introduction There has been an increased emphasis placed on understanding the initiation of deep convection during the summer months when large-scale forcing is weak or absent (e.g., Wilson et al. 1998 ). Indeed, Olsen et al. (1995) have shown a dramatic drop in the ability to forecast convection during the summer when major precipitation events occur. The main reason for this difference in skill is that winter season precipitation events are predominately associated with

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Steven E. Koch, Wayne Feltz, Frédéric Fabry, Mariusz Pagowski, Bart Geerts, Kristopher M. Bedka, David O. Miller, and James W. Wilson

.7 km versus 3.0 km), which made it possible to simulate multiple solitary waves with horizontal wavelengths smaller than 10 km; 2) the current study places a much greater emphasis on verifying the numerical prediction of solitary wave characteristics (horizontal wavelength, wave amplitude, phase speed, and structure) using a large number of remote sensing systems and aircraft data; and 3) the forcing mechanism for the bores in the present case was precipitation, not a sea breeze or topography

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