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Chris J. Walcek

.S. Air Force 3DNEPH satellite, aircraft, 'and surface-based analysis are compared with related standard meteorological observations over the easternUnited States. Cloud cover and related observations are interpolated onto the identical three-dimensional gridconsisting of 15 tropospheric levels at various horizontal resolutions ranging from (80 kin)2 to (800 km)2 forfive local noon periods during a springtime midlatitude cyclone. During the period analyzed, cloud cover maximizes near 900 mb at 35

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M. Segal, R. W. Arritt, J. Shen, C. Anderson, and M. Leuthold

simulations studying the interaction of lake breezes (LB) and background flows (e.g., Physick 1976 ; Gross and Estoque 1981; Segal and Pielke 1985 ; Arritt 1989 ) have indirectly examined various characteristics pertinent to the cloud clearing but have not addressed this situation in detail. In this note, preliminary general evaluations of the forcing of the cloud clearing for flat terrain situations are provided including conceptual elaborations, numerical model results, and observations. 2

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David R. Bachiochi and T. N. Krishnamurti

( Fig. 8 ), but may also be relevant to the North American monsoon. Figure 8 suggested a decrease in North American monsoon rains with the inclusion of PBL stratus. Since much of the monsoon rain is related to mechanical forcing by the Rocky Mountains and related ranges in the United States and Mexico, a higher-resolution model would likely give different results. Figure 11 suggests a similar improvement to the meridional wind due to the enhanced low clouds off the South American coast. This plot

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Scot T. Heckman and William R. Cotton

satellite imagery, lidar, and aircraft measurements taken during the FIREcirrus intensive field observation. Cloud-top generation zones and layering were simulated. Sensitivity simulationswere run to determine long- and shortwave radiative forcing. Also, a simulation was run with no condensateto examine cloud feedbacks on the environment. Longwave radiation appeared to be instrumental in developingweak convective-like activity, thereby increasing the cloud's optical depth.1. Introduction Cirrus

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Donald C. Norquist

1. Introduction Predictions of the cloud cover (CC) over large-scale grid areas (on the order of 100 km on a side) have long been of interest to the U.S. Air Force. Intercontinental flights common in military mobilizations and exercises and a need for mission planning for ground surveillance activities are just two of the reasons for such an interest. The air force has made a significant investment in the analysis and prediction of large-scale cloudiness. Past air force focus has primarily been

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Christopher J. Nowotarski and Paul M. Markowski

clouds. Large low-level (0–1 km) hodograph differences were observed between the near-storm and far-field environments of all supercells in the study. Despite low-level shear increases near the storm, Parker found that 0–6-km shear was relatively uniform [in contrast to simulations by Weisman et al. (1998) where shear increased over a deep layer in close proximity to supercells]. Interestingly, though nontornadic storms tended to have less favorable far-field environments, and low-level winds were

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Wayne M. Angevine, Joseph Olson, Jaymes Kenyon, William I. Gustafson Jr., Satoshi Endo, Kay Suselj, and David D. Turner

driven by forcing data prepared for the DOE LES ARM Symbiotic Simulation and Observation (LASSO) project, and compared with large-eddy simulations (LES) produced by LASSO that are driven by those same forcing data. From the wide variety of large-scale forcing combinations and LES runs available, we chose a small subset that nonetheless covers a broad range of cloud properties within the shallow cumulus range. We find good correspondence between the SCM and LES, particularly for cloud cover, liquid

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Vickal V. Kumar, Alain Protat, Peter T. May, Christian Jakob, Guillaume Penide, Sushil Kumar, and Laura Davies

land is consistent with the picture that convection in the DW regime is embedded in the large-scale forcing by the monsoon trough. In contrast, convection in the ME regimes seems to be primarily dependent on conditioning of the atmosphere by land and sea-breeze processes. For example, the majority of convective cloud activity occurs above the oceanic region in the early morning period, with peak heights at 14 km. In contrast, during the afternoon and evening periods, the convective cloud occurrence

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C-Y. J. Kao, Y. H. Hang, J. M. Reisner, and W. S. Smith

1. Introduction The numerical difficulties with unresolved cloud boundaries in a finite-differencing Eulerian framework have long been recognized. Grabowski (1989) showed that spurious oscillations of the thermodynamic and cloud variables can occur near cloud boundaries even if the monotonicity of these variables is strictly preserved during the advection. This is due to the nonlinear feedback between advected variables and their representation for forcings (i.e., condensation

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produce cloud droplets, conversion of cloud droplets to raindrops, glaciation, sublimation of water vapor, meltingof ice crystals, evaporation of cloud droplets, evaporation of raindrops, evaporation of ice crystals, and evaporation ofmelting ice crystals. The conversion and glaciation processes are paramet.erized and the drag force is assumed to beprovided by the weight of hydrometeors.The result of time integration of the model shows that, with the inclusion of the microphysical processes

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