An Ensemble Cumulus Convection Parameterization with Explicit Cloud Treatment

Wagner, Thomas; Graf, Hans‐F.

doi:10.1175/2010jas3485.1

Cited by 44 publications

(60 citation statements)

References 65 publications

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“…Therefore, dilution from the environmental entrainment does not affect the clouds as much. The inverse correlation between λ and cloud size has been used by some parameterizations [13,[39][40][41], and our observations support such use to some extent. The reason for using the reciprocal of cloud size is to make the relationship linear.…”

Section: Relationships Between λ and Cloud Propertiessupporting

confidence: 77%

An Observational Study of Entrainment Rate in Deep Convection

Guo

Zhao

et al. 2015

Atmosphere

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This study estimates entrainment rate and investigates its relationships with cloud properties in 156 deep convective clouds based on in-situ aircraft observations during the TOGA-COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment) field campaign over the western Pacific. To the authors' knowledge, this is the first study on the probability density function of entrainment rate, the relationships between entrainment rate and cloud microphysics, and the effects of dry air sources on the calculated entrainment rate in deep convection from an observational perspective. Results show that the probability density function of entrainment rate can be well fitted by lognormal, gamma or Weibull distribution, with coefficients of determination being 0.82, 0.85 and 0.80, respectively. Entrainment tends to reduce temperature, water vapor content and moist static energy in cloud due to evaporative cooling and dilution. Inspection of the relationships between entrainment rate and microphysical properties reveals a negative correlation between volume-mean radius and entrainment rate, suggesting the potential dominance of homogeneous mechanism in the clouds examined. In addition, entrainment rate and environmental water vapor content show similar tendencies of variation with the OPEN ACCESSAtmosphere 2015, 6 1363 distance of the assumed environmental air to the cloud edges. Their variation tendencies are non-monotonic due to the relatively short distance between adjacent clouds.

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Section: Relationships Between λ and Cloud Propertiessupporting

confidence: 77%

An Observational Study of Entrainment Rate in Deep Convection

Guo

Zhao

et al. 2015

Atmosphere

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“…A first example how this can be done, and still the basis for several existing convection schemes (e.g. Wagner and Graf, 2010), is the seminal work of Arakawa and Schubert (1974). They assumed that the change of the large-scale (in the model context, grid-point) properties is slow in comparison with the response of individual clouds, called quasi-equilibrium.…”

Section: Steady-plume Assumptionmentioning

confidence: 99%

Entrainment and detrainment in cumulus convection: an overview

Rooy

Bechtold

Fröhlich

et al. 2012

Quart J Royal Meteoro Soc

298

256

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Entrainment and detrainment processes have been recognised for a long time as key processes for cumulus convection and have recently witnessed a regrowth of interest mainly due to the capability of large-eddy simulations (LES) to diagnose these processes in more detail. This article has a twofold purpose. Firstly, it provides a historical overview of the past research on these mixing processes, and secondly, it highlights more recent important developments. These include both fundamental process studies using LES aiming to improve our understanding of the mixing process, but also more practical studies targeted toward an improved parametrised representation of entrainment and detrainment in large-scale models. A highlight of the fundamental studies resolves a long-lasting controversy by showing that lateral entrainment is the dominant mixing mechanism in comparison with the cloud-top entrainment in shallow cumulus convection. The more practical studies provide a wide variety of new parametrisations with sometimes conflicting approaches to the way in which the effect of the free tropospheric humidity on the lateral mixing is taken into account. An important new insight that will be highlighted is that, despite the focus in the literature on entrainment, it appears that it is rather the detrainment process that determines the vertical structure of the convection in general and the mass flux especially. Finally, in order to speed up progress and stimulate convergence in future parametrisations, stronger and more systematic use of LES is advocated.

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“…This results in the fractional entrainment at a given height being inversely proportional to the cloud radius (assuming the cloud cross section is roughly circular). This has served as the basis of many parameterizations (Arakawa and Schubert, 1974;Tiedtke, 1989;Kain and Fritsch, 1990;Wagner and Graf, 2010), some of which make the further assumption that variations in the effective radius of the cloud field are negligible and so and δ can be treated as constants (Tiedtke, 1989;Bretherton and Park, 2008). Others parameterize the effective cloud radius as proportional to the height of cloud top (Bretherton et al, 2004), or simply allow to be inversely proportional to height (de Rooy and Siebesma, 2008).…”

Section: J T Dawe and P H Austin: Direct Entrainment Distributionsmentioning

confidence: 99%

Direct entrainment and detrainment rate distributions of individual shallow cumulus clouds in an LES

Dawe

Austin

2013

Atmos. Chem. Phys.

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Probability distribution functions of shallow cumulus cloud core entrainment and detrainment rates are calculated using 4362 individual cumulus clouds isolated from LES (large eddy simulation) using a cloud tracking algorithm. Calculation of the mutual information between fractional entrainment/detrainment and a variety of mean cloud core properties suggests that fractional entrainment rate is best predicted by the mean cloud buoyancy B and the environmental buoyancy lapse rate dθ_ρ/dz at that level, while fractional detrainment is best predicted by the mean vertical velocity w and the critical mixing fraction χ_c. Fractional entrainment and detrainment rates are relatively insensitive to cloud core horizontal area, and the perimeter of horizontal cloud core sections display an a^0.73 dependence. This implies that cloud core mass entrainment flux E is proportional to cloud core cross-sectional area instead of cloud core surface area, as is generally assumed. Empirical best-fit relations for ε(B, dθ_ρ/dz and δ(w, χ_c) are found for both individual shallow cumulus clouds and cloud ensembles. It is found that clouds with high buoyancy in strong stratification experience low entrainment rates, while clouds with high vertical velocities and critical mixing fractions experience low detrainment rates

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An Ensemble Cumulus Convection Parameterization with Explicit Cloud Treatment

Cited by 44 publications

References 65 publications

An Observational Study of Entrainment Rate in Deep Convection

An Observational Study of Entrainment Rate in Deep Convection

Entrainment and detrainment in cumulus convection: an overview

Direct entrainment and detrainment rate distributions of individual shallow cumulus clouds in an LES

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