Entrainment-Mixing and Radiative Transfer Simulation in Boundary Layer Clouds

Chosson, F.; Brenguier, Jean‐Louis; Schüller, Lothar

doi:10.1175/jas3975.1

Cited by 58 publications

(65 citation statements)

References 52 publications

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“…html. This model has been extensively used for LES studies of boundary layer clouds, with the one moment and two moments microphysical schemes (Chosson, 2007;Sandu, , 2009.…”

Section: Model Setupmentioning

confidence: 99%

Supersaturation calculation in large eddy simulation models for prediction of the droplet number concentration

2012

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Abstract.A new parameterization scheme is described for calculation of supersaturation in LES models that specifically aims at the simulation of cloud condensation nuclei (CCN) activation and prediction of the droplet number concentration. The scheme is tested against current parameterizations in the framework of the Meso-NH LES model. It is shown that the saturation adjustment scheme, based on parameterizations of CCN activation in a convective updraft, overestimates the droplet concentration in the cloud core, while it cannot simulate cloud top supersaturation production due to mixing between cloudy and clear air. A supersaturation diagnostic scheme mitigates these artefacts by accounting for the presence of already condensed water in the cloud core, but it is too sensitive to supersaturation fluctuations at cloud top and produces spurious CCN activation during cloud top mixing. The proposed pseudo-prognostic scheme shows performance similar to the diagnostic one in the cloud core but significantly mitigates CCN activation at cloud top.

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“…html. This model has been extensively used for LES studies of boundary layer clouds, with the one moment and two moments microphysical schemes (Chosson, 2007;Sandu, , 2009.…”

Section: Model Setupmentioning

confidence: 99%

Supersaturation calculation in large eddy simulation models for prediction of the droplet number concentration

2012

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“…The ACEheterog case is a fractional stratocumulus case, based on the Second Aerosol Characterization Experiment (ACE-2) program which took place during 16-24 July 1997 on the Canary Islands and which had the objective of improving the description of the role of aerosols in GCMs (see Raes et al 2000). This simulation has been validated against observations in Chosson et al (2007). 4.…”

Section: Large-eddy Simulationsmentioning

confidence: 99%

“…2.3. We selected four cases of warm PBL cloud cases obtained with the Meso-NH model (Lafore et al 1998) with a resolution of 50-100 m. These simulations were validated with the results of GCSS intercomparisons for the shallow cumulus cases, and the stratocumulus cases were validated in Chosson et al (2007). These cases are presented in Sect.…”

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confidence: 99%

Evaluation of Statistical Distributions for the Parametrization of Subgrid Boundary-Layer Clouds

Perraud

Couvreux

Malardel

et al. 2011

Boundary-Layer Meteorol

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In numerical weather prediction and climate models, planetary boundary-layer (PBL) clouds are linked to subgrid-scale processes such as shallow convection. A comprehensive statistical analysis of large-eddy simulations (LES), obtained for warm PBL cloud cases, is carried out in order to characterize the distributions of the horizontal subgrid cloud variability. The production of subgrid clouds is mainly associated with the variability of the total water content. Nevertheless, in the case of PBL clouds, the temperature variability cannot be completely discarded and the saturation deficit, which summarizes both temperature and total water fluctuations, provides a better representation of the cloud variability than the total water content. The probability density functions (PDFs) of LES saturation deficit generally have the shape of a main asymmetric bell-shaped curve with a more or less distinct secondary maximum specific to each type of PBL clouds. Unimodal theoretical PDFs, even those with a flexible skewness, are not sufficient to correctly fit the LES distributions, especially the long tail that appears for cumulus clouds. They do not provide a unified approach for all cloud types. The cloud fraction and the mean cloud water content, diagnosed from these unimodal PDFs, are largely underestimated. The use of a double Gaussian distribution allows correction of these errors on cloud fields and provides a better estimation of the cloudbase and cloud-top heights. Eventually, insights for the design of a subgrid statistical cloud scheme are provided, in particular a new formulation for the weight of the two Gaussian distributions and for the standard deviation of the convective distribution.123 264 E. Perraud et al.

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“…Recent modeling studies (e.g., Chosson et al 2004Chosson et al , 2007Slawinska et al 2008) demonstrate that assumptions concerning the microphysical evolution of natural clouds, in particular the homogeneity of cloud-environment mixing, significantly affect the albedo of a field of shallow convective clouds, such as subtropical stratocumulus and trade-wind cumulus. It follows that microphysical properties of such clouds have important implications for the role of clouds in the climate system.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Subgrid-Scale Mixing in Large-Eddy Simulation of Shallow Convection

Jarecka

Grabowski

Pawłowska

2009

Journal of the Atmospheric Sciences

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This paper discusses an extension of the approach proposed previously to represent the delay of cloud water evaporation and buoyancy reversal due to the cloud-environment mixing in bulk microphysics largeeddy simulation of clouds. In the original approach, an additional equation for the mean spatial scale of cloudy filaments was introduced to represent the progress toward microscale homogenization of a volume undergoing turbulent cloud-environment mixing, with the evaporation of cloud water allowed only when the filament scale approached the Kolmogorov microscale. Here, it is shown through a posteriori analysis of model simulations that one should also predict the volume fraction of the cloudy air that was diagnosed in the original approach. The resulting model of turbulent mixing and homogenization, referred to as the l-b model, is applied in a series of shallow convection simulations using various spatial resolutions and compared to the traditional bulk model. This work represents an intermediate step in the development of a modeling framework to simulate characteristics of microphysical transformations during entrainment and subgridscale turbulent mixing.

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Entrainment-Mixing and Radiative Transfer Simulation in Boundary Layer Clouds

Cited by 58 publications

References 52 publications

Supersaturation calculation in large eddy simulation models for prediction of the droplet number concentration

Supersaturation calculation in large eddy simulation models for prediction of the droplet number concentration

Evaluation of Statistical Distributions for the Parametrization of Subgrid Boundary-Layer Clouds

Modeling of Subgrid-Scale Mixing in Large-Eddy Simulation of Shallow Convection

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