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

, and = 200 Wm −2 (0.1645 K m s −1 ), these three length scales equal L Rau = 4 km, L wm = 45 km, and L Rau2 = 90 km. Accordingly, 4 km is the finest resolution analyzed here. Atmospheric conditions compete with surface heterogeneity to influence mesoscale water vapor variability. Findell and Eltahir (2003) underlined the importance of the state of the atmosphere in determining the potential influence of the land surface on convective triggering. Alapaty et al. (1997) used a 1D soil

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

1. Introduction Previous studies of the diurnal variability of carbon dioxide (CO 2 ) focus mainly on surface processes such as photosynthesis and respiration ( Verma et al. 1989 ; Kim and Verma 1990 ; Lloyd and Taylor 1994 ), rather than on the CO 2 exchange between the atmospheric boundary layer (ABL) and the free atmosphere during daytime. This last process is driven by energy generated within the boundary layer, primarily by buoyancy, and shear at the ABL top. Vilà-Guerau de Arellano et

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Robert J. Conzemius and Evgeni Fedorovich

, the simulated evolution of the entrainment process was rather indicative of how it occurs in the atmosphere. During the early stages of the simulation, shear enhancement of entrainment was fairly large. During the middle stages, shear had little influence on entrainment, but by the end, the effects of shear were becoming important again. This cycle of shear effects somehow mirrors the change in surface buoyancy flux, which allows the relative effect of shear to be more protuberant early and late

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

and Radiation Test bed (CART; Stokes and Schwartz 1994 ) and the four First International Satellite Land Surface Climatology Project (ISLSCP) Flux Experiment (FIFE; Sellers et al. 1992 ), and SGP-97 (more information is available online at http://hydrolab.arsusda.gov/sgp97/ ). In the mid-1990s, a group of scientists organized the Cooperative Atmosphere-Surface Exchange Study (CASES; LeMone et al. 2000 , Yates et al. 2001 ) to focus on land surface interaction in the Walnut River basin in

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

period of oscillation between 0545 to 0800 CST estimated from the vertical velocity data is approximately 19 min, which equates to an average frequency of 8.6 × 10 −4 Hz. The Scorer parameter ( Lin 2007 ) was calculated using the frequency information and sounding data and the analysis showed that the atmosphere was conducive to gravity wave propagation. 5. Evolution of the convective boundary layer The continued development of the CBL after it had eroded the NBL was observed simultaneously by

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

transition of the 10.7- μ m IR T B from above to below freezing, is key for maximizing PODs, TSs, and HSSs. The reasoning for this was discussed above. 3) Cloud-top temperature (IF3) are valuable for increasing TS and HSS skills. 4) The 6.5–10.7- μ m IR T B difference is more important than the 15-min trend in this field, as well as cloud-top cooling rates, for monitoring in-cloud updrafts toward the occurrence of CI. This channel difference is highest for deep cumulus extending into middle

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

data from the International H 2 O Project (IHOP_2002; Weckwerth et al. 2004 ; LeMone et al. 2007a ) and the 1997 Cooperative Atmosphere–Surface Exchange Study (CASES-97; LeMone et al. 2000 ). Here we focus on the more sparsely vegetated IHOP_2002 western track, located in the Oklahoma Panhandle. IHOP_2002 was organized to improve prediction of warm-season precipitation; the surface and boundary layer component looked at how surface processes affect the planetary boundary layer (PBL) and

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