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Owen A. Kelley, John Stout, Michael Summers, and Edward J. Zipser

1. Introduction Over the tropical ocean, convective storm cells transport surface air to the upper troposphere in the upward leg of the planetary-scale Hadley circulation ( Riehl and Malkus 1958 ; Riehl and Simpson 1979 ). These convective cells are observed to have only modest updrafts in the low and midtroposphere ( Zipser and LeMone 1980 ; Jorgensen and LeMone 1989 ; Lucas et al. 1994 ; Wei et al. 1998 ). The modest updrafts make it seem difficult for oceanic cells to transport

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Matthew D. Parker

near a squall line’s outflow boundary, showing that the two most important processes were baroclinic generation of horizontal vorticity by the cold pool and flux of horizontal vorticity associated with the environmental wind profile. They postulated that a squall line’s optimal state would correspond to a perfectly upright updraft region, which reduced the problem to a balance between the cold pool’s strength (quantified by C , its vertically integrated buoyancy) and the environmental shear

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Hugh Morrison, John M. Peters, Adam C. Varble, Walter M. Hannah, and Scott E. Giangrande

. Dry plumes and thermals differ markedly from one another in their overall structure and entrainment characteristics (notably, about a factor-of-2-greater fractional entrainment for thermals; Morton et al. 1956 ; Scorer 1957 ), but neither describes moist cumulus convection particularly well. Latent heating associated with condensation in a conditionally unstable environment is a source of positive buoyancy aloft within moist updrafts. This contrasts with the decrease of buoyancy with height from

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Christopher S. Bretherton and Sungsu Park

the typical mass flux, cloud fraction, buoyancy, and updraft velocity of shallow cumuli. This is a key target for parameterizations and can help us understand the response of a shallow-cumulus-topped boundary layer to large-scale forcings such as sea surface temperature (SST), wind speed, and free-tropospheric conditions. A resolution of these issues for shallow convection might also be relevant to deep (heavily precipitating) convection. This is particularly true in light of LES studies showing

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John M. Peters

motion w within convective updrafts remains an elusive goal. Perhaps the simplest conceptual explanation for cumulus updrafts is that the air within them rises because it experiences an upward buoyancy force by virtue of the air within the updraft being warmer and less dense than its surroundings. In the atmospheric sciences, the buoyancy force B is formally expressed as the ratio of the density of a parcel of air to the density of its surrounding environment: , where g is gravity, is the

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Jannick Fischer and Johannes M. L. Dahl

; Roberts et al. 2016 , 2020 ; Boyer and Dahl 2020 ). However, some recent studies have focused on the second process, the intensification of the low-level 1 updraft by an upward-directed vertical perturbation pressure gradient force (VPPGF). This force tends to be dominated by the nonlinear dynamic VPPGF ( Markowski and Richardson 2014 ), which is proportional to the strength of the mesocyclone via ζ 2 , where ζ is vertical vorticity, which results from upward tilting of ambient horizontal

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John M. Peters, Hugh Morrison, Adam C. Varble, Walter M. Hannah, and Scott E. Giangrande

domain sizes (e.g., Khairoutdinov et al. 2009 ; Sherwood et al. 2013 ; Romps and Charn 2015 ; Hernandez-Deckers and Sherwood 2016 ). These LESs, combined with high-resolution cloud radar and photogrammetric studies of cumulus convection (e.g., Damiani et al. 2006 ; Damiani and Vali 2007 ; Romps and Oktem 2015 ), have indicated the widespread occurrence of thermal-like structures within cumulus updrafts. This has arguably resolved part of the plume versus thermal debate, given evidence that

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Andrew J. Heymsfield, Aaron Bansemer, Gerald Heymsfield, and Alexandre O. Fierro

they generate (see Rossow and Schiffer 1999 ). The following outlines some dominant microphysical processes operating in vigorous tropical oceanic and continentally perturbed oceanic deep convective cloud systems with peak updrafts exceeding 10 m s −1 (see our Fig. 1 and also Stith et al. 2004 ). Individual parcels of those updrafts can be transported from the boundary layer to near the tropopause ( Fig. 1a , curves 4 and 5), although most parcels of an intense convective core only reach

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Hugh Morrison

the realism of representing moist updrafts in convection schemes using the standard entraining-plume model [e.g., see the review of de Rooy et al. (2013) ]. These criticisms have often centered on the heterogeneous structure of real cloudy updrafts, in contrast to the horizontally homogeneous updraft properties typically assumed in plume-based schemes. For example, (1) does not directly address the role of detrainment near cloud edge that can occur from mixing of environmental air and cloudy

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Zachary Lebo

al. 2012 ; Seigel et al. 2013 ; Lebo and Morrison 2014 ) and observations (e.g., Rosenfeld and Woodley 2000 ; Berg et al. 2008 ; Koren et al. 2008 , 2010 ; Li et al. 2011 ; Yuan et al. 2011 ; Heiblum et al. 2012 ). These prior works have provided generally inconsistent results regarding the influence of changes in aerosol loading on precipitation and updraft velocities. Many modeling studies have found the effect of increased aerosols on updraft vigor to be small (e.g., Van den Heever

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