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Lars Umlauf, Lars Arneborg, Richard Hofmeister, and Hans Burchard

1. Introduction Submarine channels, canyons, and topographic corrugations have long been recognized for their potential importance in modifying the pathway, the dynamics, and the entrainment of dense bottom currents. Submarine channels, for example, have been identified as hot spots of gravity current entrainment at various locations ( Peters et al. 2005 ; Mauritzen et al. 2005 ; Baringer and Price 1997 ), and canyons and other small-scale corrugations are believed to play a key role for the

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Walter M. Hannah

1. Introduction Entrainment has long been recognized as a key process in moist convection ( Simpson 1971 ; Emanuel 1994 ), which limits the height and intensity through the addition of dry ambient air into a moist updraft ( Derbyshire et al. 2004 ; Del Genio 2012 ). However, accurately representing the effects of entrainment in models of moist convection remains difficult. Part of the problem is that it is unclear how to constrain the rate of mass entrainment, as well as how it is affected by

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Claudia Cenedese and Claudia Adduce

( Peters and Johns 2005 ; Peters et al. 2005 ), and the Persian Sea. Dense currents descend the continental slope for long distances before encountering the ocean bottom or interleaving at their level of neutral buoyancy. At the sill/constriction and during the descent, dense currents have been observed to entrain the surrounding ambient fluid. The final properties of their water masses are dictated by the amount and properties of the entrained fluid. Vertical profiles through the dense current have

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David M. Romps

1. Introduction Since the 1970s, bulk-plume equations have been used to diagnose convective entrainment and detrainment rates from observations of the large-scale budgets of deep and shallow convection ( Yanai et al. 1973 ; Esbensen 1978 ). More recently, bulk-plume equations have been used to diagnose the fractional rates of entrainment ϵ and detrainment δ from large-eddy simulations (LES) of shallow convection ( Siebesma and Cuijpers 1995 ; Siebesma et al. 2003 ). But the bulk

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Enoch Jo and Sonia Lasher-Trapp

1. Introduction The effects of entrainment upon the precipitation production of a supercell storm are yet to be established; such understanding is of major importance to improving precipitation forecasts to mitigate losses of life and property from short-term severe weather events ( Doswell et al. 1996 ). Over longer periods, a better understanding of entrainment also has the potential to improve estimates of cloud cover, cloud radiative forcings, and storm longevity in large

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Daniel Lecoanet and Nadir Jeevanjee

1. Introduction The rate at which cumulus clouds mix with their environment, or entrain, has long been known to be central to their dynamics ( Simpson 1983a ; Cotton 1975 ; Simpson et al. 1965 ; Stommel 1947 ). This led to a large number of studies, particularly in the early days, focused on the entrainment and dynamics of discrete, transient, convecting “thermals,” believed to be the fundamental unit of convection [see the review by Yano (2014) , as well as references given below]. With

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Anthony D. Del Genio and Jingbo Wu

2002 ; Janowiak et al. 2007 ). This has important practical ramifications, as errors in the diurnal cycle of convection produce an erroneous surface water balance and an overestimate of shortwave cloud forcing. A likely candidate for the diurnal cycle problem in GCMs is the turbulent entrainment of environmental air assumed by the models’ cumulus parameterizations. Large-eddy simulation (LES) models have been used to show that implied entrainment rates in shallow convection are considerably larger

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Sonia Lasher-Trapp, Enoch Jo, Luke R. Allen, Bryan N. Engelsen, and Robert J. Trapp

1. Introduction The American Meteorology Society’s (2020) Glossary of Meteorology defines entrainment as “the mixing of environmental air into a preexisting organized air current so that the environmental air becomes part of the current.” In an active cumulus cloud, the “preexisting organized air current” is the cloud updraft that originates below its base. Overturning eddies at upper levels at the cloud edges mix in drier “environmental air” that results in evaporation and sublimation of

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Alessandra S. Lanotte and Irene M. Mazzitelli

monoxide or, for example, that of the humidity field under neutral conditions. In the atmospheric boundary layer, in addition to the physics of turbulent transport, both surface and entrainment physics are crucial to scalar mixing. Scalar fields are commonly emitted close to the ground and are dispersed by turbulence within the mixed layer. The capping inversion acts as a lid to the rise of thermals and to diffusion of scalars in the free atmosphere. On the other hand, entrainment is the mechanism

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Christopher S. Bretherton and Sungsu Park

undilute cloudy updrafts rising from the boundary layer ( Rennó and Ingersoll 1996 ; Emanuel and Bister 1996 ; Craig 1999 ). In this paper, we construct a new bulk trade-cumulus boundary layer model that suggests insights into these issues. It is a refinement of Albrecht et al.’s (1979) model (hereafter called Albrecht’s model), which corrects internal inconsistencies in that model. It is based on an entraining–detraining bulk plume model for the ensemble mixing dynamics of cumulus convection

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