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Jongil Han and Hua-Lu Pan

the updraft and thus enhancing mass exchange between the cloud and environment. However, initial tests have indicated that the empirical parameterization for the convection-induced pressure gradient force has a negligible effect on the hurricane intensity forecast. In this study, we test the parameterization of cloud pressure gradients proposed by Wu and Yanai (1994) and Gregory et al. (1997) . In the parameterization the pressure gradient force is assumed to be proportional to the product of

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Lígia R. Bernardet and William R. Cotton

boundary layer in derecho maintenance. The outline of this paper is as follows. In section 2 a review of the observations is presented. A description of the configuration of the numerical model used in this study is presented in section 3 . The evolution of the simulation is presented in section 4 , with emphasis on both the mesoscale environment and the cloud-scale results. Section 5 describes the techniques used to analyze the simulation results: a pressure perturbation decomposition and a

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Daniel T. Dawson II, Brett Roberts, and Ming Xue

PPGF is specified in this case by the constraint of geostrophic balance. A standard method in most idealized cloud models is to define the model base state using the geostrophic initial environment as defined here. Then, ( U , V ) = ( U g , V g ) and from (3) the environmental horizontal winds remain steady in time, as desired. Otherwise, it is easy to see from (3) that this is mathematically equivalent to applying the Coriolis force only to the perturbation winds relative to this initial

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, intense updraft to bring the low-level moistair into the cloud, nnd a vertical wind shear which steers the cumulonimbus cell with a velocity which is considerablydifferent from that of t,he low-level winds. The Magnus effect involving the steering current and the spiraling up-draft is considered to be the force which directs the hook-echo circulation at low levels toward the sorlt,hawtcrncdgc of t,he major thunderstorm cell. A kinematic diagram with the absolute tangential speed and the radius of

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T. D. Keenan and R. E. Carbone

. Fig . 5. Selected sample satellite-derived Hovmöller diagrams for (a) midlatitude band 30°–40°S, (b) subtropical band 20°–30°S, and (c) tropical band 10°–20°S. Percentage of high cloud ( P HC ) is shown to the right with warmer colors indicating higher frequency. Cross sections of maximum surface elevation within each band are also shown below the top Hovmöller diagrams. Shaded ellipse areas denote major “forcing zones.” See text for discussion relating to shaded areas and features. Fig . 5

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Mark Smalley, Kay Sušelj, Matthew Lebsock, and Joao Teixeira

sensitivity ( Boucher et al. 2013 ). Because subtropical MBL clouds are characterized by a subtle balance between several physical processes that include large-scale dynamics, convective- and turbulent-scale mixing, radiation, microphysics, and aerosols ( Wood 2012 ), their representation in GCMs requires an accurate description and coupling of these processes. The transition between subtropical stratocumulus to cumulus cloud regimes is particularly difficult, as it is governed by small changes of forcing

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Frederick Sanders

of smallor negative stability in the northwestern portions of the major cloud mass. Strong (moist or dry) symmetricstability was indicated, however, in the inner portions of the developing cyclonic circulation. The small stability initially accompanying the frontogenetical forcing was consistent with recent analytic andnumerical models showing a vigorous and concentrated frontal updraft. Details of the structure shown by theDoppler data, and in particular the prominence of the bandedness at

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James T. Moore and Pamela D. Blakley

frontogenetical forcing. Conditional symmetric instability was also diagnosed in the region of the updraft of the direct thermal circulation. This "slantwise convection", diagnosed where surfaces of constant geostrophic angular momentumslope less than surfaces of equivalent potential temperature, is believed to have both increased the intensity ofthe updraft and decreased the scale length of the phenomena. The conditional symmetric instability may havehelped to create pulselike eruptions of elevated cloud

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Yang Yang and Yi-Leng Chen

contrast with the longest duration of anabatic/upslope flow along the Kona leeside coastline ( Yang and Chen 2003 ; Chen and Nash 1994 ). Furthermore, in addition to feedback effects of latent heat release ( Chen and Feng 2001 ), the variations of orographic cloud cover and the amount of water vapor in the atmosphere due to different terrain/mountain heights could affect the thermal forcing from the surface and feed back to the island-scale airflow and weather. Therefore, without careful consideration

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Donald C. Norquist

Force GlobalWeather Central (AFGWC) cloud analysis procedure(formerly called 3DNEPH, now RTNEPH) as described by Fye (1978). Henderson-Sellers and Hughes(1985) have found a generally good agreement in total'cloud amounts to exist between these cloud analysesand other published cloud climatologies. Because ofthe high spatial resolution of these cloud analyses(46.325 km in horizontal, 15 layers through 100 mbin the vertical), a procedure of converting the percentcloud cover information to relative

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