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Edward I. Tollerud, Fernando Caracena, Steven E. Koch, Brian D. Jamison, R. Michael Hardesty, Brandi J. McCarty, Christoph Kiemle, Randall S. Collander, Diana L. Bartels, Steven Albers, Brent Shaw, Daniel L. Birkenheuer, and W. Alan Brewer

1. Introduction Previous studies of the low-level jet (LLJ) have helped to establish its role as the major conveyor of low-level moisture from the Gulf of Mexico into the central United States ( Stensrud 1996 ; Higgins et al. 1996 ). Higgins et al. (1997) estimate that the contribution of the LLJ to low-level moisture transport over the central plains is almost 50% above average non-LLJ values. A major factor in the LLJ contribution to central plains precipitation is the relationship between

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

the grass vegetation became the dominant factor in the CO 2 diurnal variability. The majority of the ABL studies concerned with the vertical structure of the turbulent fluxes and entrainment assume a homogeneous surface. However, the land surface can be rather heterogeneous, resulting in horizontal variability in the surface fluxes. The entrainment of heat, moisture, and carbon dioxide could be influenced by the variability of the surface properties as well. Analysis of idealized large

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

1. Introduction Sensitivity of continental precipitation to land surface conditions, including soil moisture, has been established for a wide range of time scales. These time scales range from less than a single diurnal cycle through influences on the timing and location of deep convection initiation (e.g., Lanicci et al. 1987 ; Shaw et al. 1997 ; Ziegler et al. 1997 ; Trier et al. 2004 ; Holt et al. 2006 ; Sutton et al. 2006 ) to seasonal via impacts of persistent soil moisture anomalies

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Roger M. Wakimoto and Hanne V. Murphey

. The airborne Doppler radar flew a box pattern around the dryline with along-boundary legs being ∼90 km long. Accordingly, the variability of the wind field with high spatial resolution was well documented. No moist convection developed within the intensive observation region on this day as noted by Cai et al. (2006) . Detailed wind, temperature, and moisture fields associated with this dryline, however, provide an extensive dataset that has only been available for a few case studies in the

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

vapor variability has been stressed as an important condition for convection. Crook (1996) , Wulfmeyer et al. (2006) , and Stirling and Petch (2004) have shown that the initiation of convection is strongly tied to the accurate estimate of water vapor within the boundary layer (BL). In the latter study, the authors demonstrated that the existence of moisture fluctuations accelerates the initiation of deep convection by 1–3 h, and that convective initiation was most sensitive to BL moisture

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

values, we estimated the difference between T s and 2-m temperature T 0 by subtracting the best-fit straight line to T 0 from the surface sites (average of 1815 and 1845 UTC) from the best-fit quadratic for the aircraft T s for the flight leg centered at 1830 UTC. The aircraft normalized differential vegetation index (NDVI) is from Exotech radiometer data. The soil and vegetation data used here were collected in several different ways. Recorded values of soil moisture at 5 cm at the NCAR

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

convection, both through the creation of upwelling regions favorable for storm formation and through destabilization through enhanced CBL growth (e.g., Anthes 1984 ; Segal et al. 1988 ; Pielke et al. 1991 ; Chen et al. 2001 ; Trier et al. 2004 ). The relationship of the surface vegetation and soil moisture to the surface sensible and latent heat fluxes in the Southern Great Plains (SGP) has been studied extensively using data especially from the SGP Atmospheric Radiation Measurements (ARM) Cloud

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Roger M. Wakimoto and Hanne V. Murphey

June was associated with the weakest kinematic discontinuity observed during the experiment; however, there was a substantial moisture gradient across the boundary as shown by Cai et al. (2006 ; see Fig. 1d ). No storms developed along the dryline on this day. An approximate west–east-oriented boundary along the Oklahoma–Kansas border was produced by outflow from a mesoscale convective system on 12 June ( Fig. 1e ). A dryline intersected the outflow just east of a circulation associated with

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

, hereafter Part I) , we focused on comparisons of observed and simulated surface fluxes, CBL thermodynamics, and CBL depth, and found that The Noah LSM produced an east–west gradient in H and LE consistent with the modeled soil moisture pattern, but not the observed variation associated with land cover, due to shortcomings in the input land-use and land-cover table. While modeled mean LE values and horizontal variation in the CBL depth compared reasonably well with

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

studies showing horizontal maps of the moisture in the CBL from an airborne water vapor lidar. The structure of the paper is as follows. The layout and description of instrumentation are described in section 2 and the general meteorological situation in section 3 . Observations of the evolution of the early morning boundary layer are presented in section 4 , the development of the convective boundary layer in section 5 , and the characteristics of the open cells in section 6 . A summary of the

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