Influence of the Subcloud Layer on the Development of a Deep Convective Ensemble

Böing, Steven J.; Jonker, Harm J. J.; Siebesma, A. Pier; Grabowski, Wojciech W.

doi:10.1175/jas-d-11-0317.1

Cited by 124 publications

(173 citation statements)

References 53 publications

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“…Most importantly, precipitation triggers downdraughts that promote the formation of cold pools. The mesoscale organisation associated with the cold pools supports deep convection and accelerates the transition from shallow to deep convection (Böing et al, 2012). Attempts are being made to include this process by adding explicit relations to tighten ε and δ to precipitation or its evaporation (section 4.3; Hohenegger and Bretherton, 2011;Mapes and Neale, 2011).…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Entrainment and detrainment in cumulus convection: an overview

Rooy

Bechtold

Fröhlich

et al. 2012

Quart J Royal Meteoro Soc

284

252

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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: Conclusion and Discussionmentioning

confidence: 99%

Entrainment and detrainment in cumulus convection: an overview

Rooy

Bechtold

Fröhlich

et al. 2012

Quart J Royal Meteoro Soc

284

252

View full text Add to dashboard Cite

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“…In HET-XL the diagnosed entrainment is about 30% smaller compared to HOM. The observed variations in terms of entrainment rate are quite large (see Böing et al 2012). Such large differences in the entrainment would speak for their inclusion in a convective parameterization.…”

Section: Mechanisms Generating the Cloud Size Distributionmentioning

confidence: 96%

The Influence of Land Surface Heterogeneities on Cloud Size Development

Rieck

Hohenegger

Heerwaarden

2014

Monthly Weather Review

120

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This study analyzes the effects of land surface heterogeneities at various horizontal scales on the transition from shallow to deep convection and on the cloud size distribution. An idealized case of midlatitude summertime convection is simulated by means of large-eddy simulations coupled to an interactive land surface. The transition is accelerated over heterogeneous surfaces. The simulation with an intermediate patch size of 12.8 km exhibits the fastest transition with a transition time two-thirds that over a homogeneous surface. A similar timing is observed for the precipitation onset whereas the total accumulated rainfall tends to increase with patch size. The cloud size distribution can be approximated by a power law with a scale break. The exponent of the power law is independent of the heterogeneity scale, implying a similar cloud cover between the simulations. In contrast, the scale break varies with patch size. The size of the largest clouds does not scale with the boundary layer height, although their maximum size scales with the patch size. Finally, the idea that larger clouds grow faster, known from homogeneous surface conditions, is not fully valid over heterogeneous surfaces. These various aspects can be understood from the complex interplay between the characteristics of the triggered mesoscale circulations and a cloud development acting in response to the diurnal cycle in surface heating. The results also call for adequate representation of such effects in convective parameterizations.

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“…Cooling by evaporation of precipitation below convective clouds results in cold pools, which are characterized by a near-surface horizontal flow of relatively cold and dry air. A few studies (e.g., Grabowski et al 2006;Khairoutdinov and Randall 2006;Böing et al 2012;Bao and Zhang 2013;Schlemmer and Hohenegger 2014) investigated how precipitation-driven cold pools aid the transition from shallow to deep convection. Vertical lifting and moisture accumulation at the leading edge of the cold pool play an important role.…”

Section: October 2016 P a N O S E T T I E T A Lmentioning

confidence: 99%

Idealized Large-Eddy and Convection-Resolving Simulations of Moist Convection over Mountainous Terrain

Panosetti

Böing

Schlemmer

et al. 2016

Journal of the Atmospheric Sciences

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On summertime fair-weather days, thermally driven wind systems play an important role in determining the initiation of convection and the occurrence of localized precipitation episodes over mountainous terrain. This study compares the mechanisms of convection initiation and precipitation development within a thermally driven flow over an idealized double-ridge system in large-eddy (LESs) and convection-resolving (CRM) simulations. First, LES at a horizontal grid spacing of 200 m is employed to analyze the developing circulations and associated clouds and precipitation. Second, CRM simulations at horizontal grid length of 1 km are conducted to evaluate the performance of a kilometer-scale model in reproducing the discussed mechanisms.Mass convergence and a weaker inhibition over the two ridges flanking the valley combine with water vapor advection by upslope winds to initiate deep convection. In the CRM simulations, the spatial distribution of clouds and precipitation is generally well captured. However, if the mountains are high enough to force the thermally driven flow into an elevated mixed layer, the transition to deep convection occurs faster, precipitation is generated earlier, and surface rainfall rates are higher compared to the LES. Vertical turbulent fluxes remain largely unresolved in the CRM simulations and are underestimated by the model, leading to stronger upslope winds and increased horizontal moisture advection toward the mountain summits. The choice of the turbulence scheme and the employment of a shallow convection parameterization in the CRM simulations change the strength of the upslope winds, thereby influencing the simulated timing and intensity of convective precipitation.

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Influence of the Subcloud Layer on the Development of a Deep Convective Ensemble

Cited by 124 publications

References 53 publications

Entrainment and detrainment in cumulus convection: an overview

Entrainment and detrainment in cumulus convection: an overview

The Influence of Land Surface Heterogeneities on Cloud Size Development

Idealized Large-Eddy and Convection-Resolving Simulations of Moist Convection over Mountainous Terrain

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