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F. Chevallier and G. Kelly

caused by deficiencies of the cloud radiative forcing in the model. The cloud radiative forcing is defined as the difference between the clear-sky brightness temperature and the full-sky brightness temperature. Focusing on Meteosat-7, Table 2 presents some statistics (mean and standard deviations) about the temporal evolution of the spatial correlation between the observed and the simulated images at 1200 UTC over an extended period of time: from 12 October to 31 December 2000. The correlations

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Young-Hwa Byun and Song-You Hong

-range forecast (MRF) model ( Grell 1993 ; Pan and Wu 1995 ; Hong and Pan 1998 ). The subgrid-scale convective processes of the SAS scheme tested in this study comprise three components: 1) the random selection of cloud top, 2) the inclusion of convective momentum transport, and 3) a revised large-scale destabilization effect considering synoptic-scale forcing. The first two components have been operational at NCEP since 2001, and have exhibited good performance for medium-range forecasts ( Global Climate

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C. P. Chang, F. T. Jacobs, and B. B. Edwards

divergence cloud brightness with seasonal mean bright ness removed O'div -K= monthly proportionality constant.When this equivalent divergence is used as forcing of(2), it will be referred to as "brightness forcing" in thediscussion of the experiments in Section 4.540 MON.THLY WEATHER REVIEW VoLu~ 103'12.5 125E(a)150

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John Molinari

. Much information can be gained, however, by examining thelimiting behavior of an approach under strong external forcing. a. Without entrainment Four formulations for the b parameter are tested: 1) b = (J + 1)/21 (Kanamitsu, 1975) 2) b = (I - RH)/(I - RHc); b = 1 for RH < RHc (Anthes, 1977a) 3) b = constant = initial vah,e 4) b --- [(J + I)/1][Qq/(Qq + Qo + J)] (present study).In case 2, the overbar indicates a vertical average overthe cloud layer, and critical relative humidity

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Y. Sud and A. Molod

sensitivity of the simulated July cirt~lation to modifications in the parameterization of dry and moistconvection, evaporation from falling raindrops, and cloud-radiation interaction is examined with the GLA(Goddard Laboratory for Atmospheres) GCM (general drculation model). Inferences are based on several 47day summer integrations using the same prescribed boundary forcings. The Arakawa-sehubert cumulus parameterization, together with a more realistic dry convective mixing calculation that allowed

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Cathy J. Kessinger, David B. Parsons, and James W. Wilson

, three misocyclones, a miso-anticyclone, and horizontal vortex circulations, in addition to heavy rain, hail, and strong winds. These interrelated features produce complex flow patterns within the storm on small spatial and temporal scales. In this paper, we document the four-dimensional structure and evolu tion of these features and discuss forcing mechanisms of the downdrafts. Multiple Doppler analyses are used to examine the kinematic and reflectivity fields below cloud base. Three

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J. Cory Demko and Bart Geerts

cumulus convection can temporarily overwhelm this convergence around the mountain. The diurnal trend of surface MSC is rather bell shaped on the cloud-free day (12 July), but it shows two maxima straddling the period of most active cumulus convection and light precipitation over the mountain on the other day (9 July). And third, MSC in the lower troposphere is forced by a hydrostatic perturbation pressure gradient force toward the mountain. This forcing is solenoidal (i.e., it is due to a warm anomaly

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Hubert Gallée

on its forcing by katabaticwinds. The three-dimensional version of the meso-3,-scale primitive equation model ModUle AtmosphtriqueRtgional is used in which a representation of cloud microphysical processes has been introduced. Idealizedboundary conditions are prescribed. In particular, the ocean is assumed to be completely ice-free or partially icecovered. The former case corresponds to a fall situation that coincides with the climatological maximum ofestimated precipitation at McMurdo Station on

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Lidia Huaman, Courtney Schumacher, and George N. Kiladis

. This paper analyzes the characteristics and extratropical forcing of EPDs in the tropical Pacific during boreal winter (DJF) and spring (MAM), as well as associated variations in the meridional overturning circulation in the east Pacific. We utilize brightness temperature ( T b ) for cloud properties, satellite precipitation for convective intensity, and reanalysis data for dynamical fields. We focus on DJF and MAM due to the strong NH wave activity during these seasons. This article is organized

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Peter J. Pokrandt, Gregory J. Tripoli, and David D. Houghton

disturbance. The primary model run has a nestedfine mesh prescribed to follow the exit region cloudband that evolved into the comma cloud, in order toexamine the synoptic-scale forcings that may haveformed the waves. Comparison between results fromthis and other simulations and satellite observationsleads us to suggest a different mechanism for the generation of these waves related to the formation of a PVanomaly at midlevels. The next section presents a discussion of previous studies of this case

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