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George S. Young and Todd D. Sikora

northwest of the Gulf Stream North Wall yields a bulk surface sensible heat flux of 0 W m −2 while the inferred value over the Gulf Stream was 120 W m −2 . Thus, the thermodynamic forcing was similar to that in the previously discussed mesoscale band cases. The synoptic setting was likewise similar with cold advection occurring in the northerly and northwesterly boundary layer flow west of a cold front (not shown). Yet, despite these similarities, the 20 March case lacked mesoscale- β cloud bands. The

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Bruce B. Ross

diabatic heating on the development of convective systems have beeninvestigated using a simplified numerical model to simulate the squall line and the convective system precedingit that occurred over Texas and Oklahoma on 10-11 April 1979. A simulation run without including latentheat showed both systems to be initiated and maintained by convergence produced by larger-seale forcing. Thefirst cloud system formed downwind of the convergence zone that was produced by the confluence ofai~treamsalong a do

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Xiangqian Wu and William L. Smith

reduction is inadequate, possibly because of the inability of the current cloud scheme todeal with convective activity. The optimization procedure is both stable and sensitive. The largest impact of the optimized cloud diagnosisis on the forecast of surface temperature. The impact on the forecast of other model variables is insignificant.This is partly due to the model's highly simplified treatment of cloud and to the short time of model integrationcompared to the time scale of radiative forcing

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Alfred J. Garrett

, a convective boundary layer,solar and longwave radiation, a soil layer and a parameterized forest layer. The model simulated the growthof the convective boundary layer and convective clouds on days when solar heating was primarily responsiblefor the convection, and meso- or synoptic-scale forcing was weak. The simulations agreed more closely withobservations, and were generally more realistic when the parameterized forest layer and interactions betweenclouds and radiation fluxes were included

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Georgios Matheou and João Teixeira

1. Introduction Stratocumulus clouds (Sc) have a large impact on Earth’s radiative balance because they cover about one-quarter of Earth’s surface and strongly reflect incoming solar radiation while having a small effect on outgoing longwave radiation (e.g., Hartmann et al. 1992 ; Bretherton 1997 ; Stevens 2005 ; Wood 2012 ). Sc is one of the most studied cloud systems ( Stevens 2005 ) with several observational campaigns (e.g., Lenschow et al. 1988 ; Stevens et al. 2003a ; Malinowski et

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Bjorn Stevens, Chin-Hoh Moeng, Andrew S. Ackerman, Christopher S. Bretherton, Andreas Chlond, Stephan de Roode, James Edwards, Jean-Christophe Golaz, Hongli Jiang, Marat Khairoutdinov, Michael P. Kirkpatrick, David C. Lewellen, Adrian Lock, Frank Müller, David E. Stevens, Eoin Whelan, and Ping Zhu

et al. 2001 ) have raised serious questions about the ability of LES to realistically represent cloud-topped PBLs capped by a strong temperature inversion. In a study by Moeng et al. (1996) , 12 large-eddy simulation codes were run for identical initial conditions and forcings loosely based on a cloud layer observed during the First International Satellite Cloud Climatology Project (ISCCP) regional field study ( Albrecht et al. 1988 ). An evaluation of the simulations revealed marked differences

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Richard Rotunno and Joseph B. Klemp

by horizontal buoyancy gradient, creates low pressure on the updraft flanks at midlevels, thereby forcing vertical motion on the flanks. These are, essentially, nonlinear effects. Wil helmson and Klemp (1978) attributed storm splitting to an accumulation of rainwater on the axis of the initial updraft. However, recomputing the cloud model simulation shown in Fig. 2a with rain pro cesses turned off, splitting did occur, although it took much longer to develop and the split storms moved apart much

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Fang-Ching Chien and Ying-Hwa Kuo

fine enough to reproduce rope clouds of <5 km width. The simulation also reproduced the cloud-free area behind the front off the east coast near Hualien. Clouds were suppressed because westerly flow passed through the gap between the two major peaks of the CMR and resulted in subsidence near this region. As cold air surged southward along the east coast, the increasing westward Coriolis force induced a landward acceleration. The cold air gradually piled up against the mountains, resulting in a

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Robert A. Weisman

regions during warm season lee-trough episodes in the southern Appalachians areexamined in this study. A composite of cloud-to-ground lightning data during 1985 lee trough cases indicatesthat the time of maximum activity is the late afernoon. A stratification of cases by the strength of the largescale forcing indicauxt that both the strength and location of afternoon convection depended on synoptic- andsubsynoptic.scale process. Days with strong or moderate cyclonic forcing produced the most lightning

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Patrick A. Haines and Wen-Yih Sun

-dimensional equationfor the azimuthal vorticity over the cloud radius is described. The equations are reduced to one dimension inthe vertical direction by assuming that the streamfunction is oscillatory and a function of r only allowing thismodel to incorporate the nonhydrostatic pressure gradient force. It also includes an empirical buoyancy correctionto account for vertical wind shear; the correction is based on application of the Klemp-Wilhelmson convectivecloud model to a variety of buoyancy and wind

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