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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

conservation of total energy following the 3D flow); is the velocity vector, ω is the pressure vertical velocity, and α is the specific volume. In (3) , the first two terms on the right-hand side represent baroclinic and barotropic conversion, respectively. The third term on the right-hand side also represents an energy transfer between the mean flow and the eddies, but averages out to zero in the time mean. Following Orlanski and Sheldon (1993) , the energy flux can be written as follows: where

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Robert Wood

are major differences in the seasonal phase between the western and the eastern sides of the midlatitude North Atlantic and Pacific Ocean, with a wintertime peak over the western sides and summertime peaks over the eastern sides ( Weaver and Ramanathan 1997 ). This probably reflects the greater importance of surface sensible heat flux (e.g., during wintertime cold-air outbreaks) for stratocumulus on the western side. Over the tropical oceans, there does not appear to be a systematic favored month

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Markus Gross, Hui Wan, Philip J. Rasch, Peter M. Caldwell, David L. Williamson, Daniel Klocke, Christiane Jablonowski, Diana R. Thatcher, Nigel Wood, Mike Cullen, Bob Beare, Martin Willett, Florian Lemarié, Eric Blayo, Sylvie Malardel, Piet Termonia, Almut Gassmann, Peter H. Lauritzen, Hans Johansen, Colin M. Zarzycki, Koichi Sakaguchi, and Ruby Leung

from radiative heating profiles is considered in the calculation of entrainment at the top of the cloudy boundary layer in the turbulence schemes by Lock et al. (2000) and Bretherton and Park (2009) , which improves the radiation–turbulence coupling from the perspective of time stepping. Some modern parameterizations are designed to handle multiple atmospheric processes in a unified way. Examples include the eddy diffusivity–mass flux (EDMF) scheme of Siebesma et al. (2007) and the Cloud

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J. R. Garratt

coefficient--in practice considerableflexibility is retained for adjusting the magnitude ofthe stress term to achieve balance, mainly due to thelack of reliable mean monthly surface and geostrophicwinds over the entire globe (particularly over remoteocean areas) and uncertainty in thermal wind.2. Relations and definitions In the constant flux layer of the atmosphere adjacentto a horizontally homogeneous surface, the local surfacestress may be written in terms of the surface windV(z)'at height z (Taylor

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T. N. Krishnamurti

to this effect because the oceanic responseto solar radiation has a lag of one to two months, whilethe observed cooling starts almost immediately afterthe onset of strong winds. 2) Southward flux of heat by ocean currents is contributed by clockwise oceanic eddies over the westernArabian Sea. This was estimated by Diiing and Leetmaa (1980); the related cooling of the northern ArabianSea by equatorward transport appears to be quite small. 3) Coastal upwelling and downstream shedding ofcold

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Robert A. Houze Jr.

transport dominated as the depression approached tropical storm stage. Zipser and Gautier (1978) further noted that the mesoscale convergence feeding the massive convective updraft present in the MCS they investigated was sufficient to account for the intensification of the synoptic-scale depression vortex in which the MCS was located. A sharp increase of upward mass flux with height occurred throughout the lower portion of the updraft in the pre-Ophelia convection (see the isolines of the vertical

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Tammy M. Weckwerth and David B. Parsons

Horizontal convective rolls are a common form of boundary layer convection manifested as counterrotating vortices about the horizontally oriented axis. Clouds often form atop the updraft branches of rolls (e.g., Kuettner 1959 , 1971 ; LeMone and Pennell 1976 ; Christian and Wakimoto 1989 ). Rolls and cloud streets can extend hundreds of kilometers and last several hours. The conditions necessary for roll development and maintenance are surface-layer heat flux, some minimal low-level wind shear, and

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Julia H. Keller, Christian M. Grams, Michael Riemer, Heather M. Archambault, Lance Bosart, James D. Doyle, Jenni L. Evans, Thomas J. Galarneau Jr., Kyle Griffin, Patrick A. Harr, Naoko Kitabatake, Ron McTaggart-Cowan, Florian Pantillon, Julian F. Quinting, Carolyn A. Reynolds, Elizabeth A. Ritchie, Ryan D. Torn, and Fuqing Zhang

moves poleward and starts to interact with the midlatitude flow ( Fig. 1a ). This results in the formation of a jet streak ( Fig. 1b ) and a poleward deflection of the jet near the transitioning cyclone in conjunction with the development of a ridge–trough couplet ( Fig. 1b ). At the same time, a region of enhanced moisture flux—a so-called atmospheric river ( Zhu and Newell 1998 )—forms ahead of the downstream trough. The ridge–trough couplet continues to amplify, a new cyclone develops farther

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John Molinari and Michael Dudek

. A model that allowedcondensation only upon grid-scale saturation wouldfail to reproduce this heat source. (iii) Large vertical fluxes of heat, moisture, andother quantities by cumulus convection occur on scalesunresolvable by hydrostatic model grids. A model thatdid not implicitly include such subgrid-scale sourceterms could not accurately predict grid-scale evolutionwhen convection was active. The sum of net condensation heating (or moistening) in the column [(ii) above] and convective

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Dayton G. Vincent

westerlyjet in question; it is centered at about 25-S, 170-W, andhas a maximum strength in excess of 30 m s-L Theremaining panels depict contributions to the acceleration of the zonal wind by the two most important termsin the localized E-P flux equations of Trenberth(1986). These are the Coriolis force due to the diabatically driven divergent meridional wind (fv*) and theE-P flux divergence (V .E,), which is a measure of thenet mean forcing by eddies on the time mean flow. Itis seen that the tropical

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