Adaptive detrainment in a convective parametrization

Derbyshire, S. H.; Maidens, Anna; Milton, Sean; Stratton, Rachel; Willett, Martin

doi:10.1002/qj.875

Cited by 95 publications

(93 citation statements)

References 27 publications

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“…In line with the arguments mentioned in this subsection, an adaptive detrainment parametrization has been proposed very recently by Derbyshire et al (2011). LES results in their study (their Figures 5 and 6) confirm that δ varies much more strongly with environmental RH than ε.…”

Section: Parametrising the Shape Of The Shallow Mass Flux Profilesupporting

confidence: 81%

“…Figure 9 shows the entrainment profiles with (26) for the different RH regimes in Derbyshire et al (2004). LES results presented by Derbyshire et al (2011) (Figure 5) for the same RH regimes also reveal increasing ε values with decreasing RH in the lower part of the cloud layer. Fractional detrainment rates are parametrised differently, namely as the sum of a vertically constant turbulent detrainment and a term that is proportional to the decrease in updraught kinetic energy when the buoyancy is negative (Bechtold et al, 2008).…”

Section: Rh-dependent Entrainmentmentioning

confidence: 74%

“…Numerous LES studies support this by revealing order-of-magnitude larger variations from case to case and hour to hour in δ than in ε (e.g. Figure 8; Jonker et al, 2006;Derbyshire et al, 2011). Nevertheless, its implication for parametrising convection is almost never used or even discussed.…”

Section: Parametrising the Shape Of The Shallow Mass Flux Profilementioning

confidence: 99%

See 2 more Smart Citations

Entrainment and detrainment in cumulus convection: an overview

Rooy

Bechtold

Fröhlich

et al. 2012

Quart J Royal Meteoro Soc

304

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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Section: Parametrising the Shape Of The Shallow Mass Flux Profilesupporting

confidence: 81%

Section: Rh-dependent Entrainmentmentioning

confidence: 74%

See 1 more Smart Citation

Entrainment and detrainment in cumulus convection: an overview

Rooy

Bechtold

Fröhlich

et al. 2012

Quart J Royal Meteoro Soc

304

256

View full text Add to dashboard Cite

show abstract

“…This may simply be an alternative way of inhibiting the convection in low-RH environments, (where our CRM results achieve this through higher detrainment rates), but it does suggest that caution should be applied about the universality of the relationship we find between entrainment and RH, and that studies of convection in different environments particularly over the sea would merit further investigation. The detrainment dependence on RH measured here is found to be about four times stronger than is currently used in the UM, and there is evidence from Derbyshire et al(2011) that this is also the case for deep convection at equilibrium. We have not investigated the buoyancy of the detrained air to determine whether the term we call 'mixing detrainment' is detraining with the average plume buoyancy.…”

Section: Discussionsupporting

confidence: 46%

“…Forced detrainment is applied when the plume buoyancy excess starts to decrease with height, and follows Derbyshire et al(2011). It is given by…”

Section: Unified Model Mass Flux Schemementioning

confidence: 99%

Entrainment processes in the diurnal cycle of deep convection over land

Stirling

Stratton

2011

Quart J Royal Meteoro Soc

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In this article we show that entrainment during the developing stages of deep convection over land is much higher than convection at equilibrium. A series of idealised cloud-resolving model simulations are performed for a range of environmental conditions, and these show that the interaction with the environment via the entrainment and detrainment rates gradually decreases as the day progresses, reverting to the values found at equilibrium. The entrainment and detrainment rates are themselves found to depend on the environmental humidity and stability, and are also strongly linked to cloud size, suggesting that the representation of the horizontal growth of clouds in convective parametrizations is important for the representation of the diurnal cycle. We propose a simple new entrainment and detrainment formulation to take account of these findings, and show that this

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Near‐cloud aerosols in monsoon environment and its impact on radiative forcing

et al. 2015

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In order to understand the near-cloud aerosol properties and their impact on radiative forcing, we utilized in situ aircraft measurements of aerosol particles and cloud droplets during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment carried out over the Indian subcontinent in the monsoon season. From the measurement of aerosol size distribution of diameter range from 0.1 to 50 μm, we reported that aerosol concentrations could be enhanced by 81% and the effective diameter (d eff , μm) by a factor of 2 near the cloud edges when compared with regions far from the cloud. These enhanced aerosol concentrations are a function of the relative humidity (RH) in the cloud-free zone, attributed to mixing and entrainment processes in the cloud edges. It is also found that for warm clouds, RH increases exponentially in the near-cloud regions. In addition, d eff was increased linearly with RH. Through model simulations, we found that aerosol optical depth decreases with distance from the cloud edge. Further, aerosols in cloud edges were found to increase the reflected flux by 20% compared to cloud-free regions, thus brightening the near-cloud areas.

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Adaptive detrainment in a convective parametrization

Cited by 95 publications

References 27 publications

Entrainment and detrainment in cumulus convection: an overview

Entrainment and detrainment in cumulus convection: an overview

Entrainment processes in the diurnal cycle of deep convection over land

Near‐cloud aerosols in monsoon environment and its impact on radiative forcing

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