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    Modeling of Stratocumulus Cloud Layers in a Large Eddy Simulation Model with Explicit Microphysics

    Source: Journal of the Atmospheric Sciences:;1995:;Volume( 052 ):;issue: 016::page 2923
    Author:
    Kogan, Y. L.
    ,
    Khairoutdinov, M. P.
    ,
    Lilly, D. K.
    ,
    Kogan, Z. N.
    ,
    Liu, Qingfu
    DOI: 10.1175/1520-0469(1995)052<2923:MOSCLI>2.0.CO;2
    Publisher: American Meteorological Society
    Abstract: A new large eddy simulation (LES) stratocumulus cloud model with an explicit formulation of micro-physical processes has been developed, and the results from three large eddy simulations are presented to illustrate the effects of the stratocumulus-topped boundary layer (STBL) dynamics on cloud microphysical parameters. The simulations represent cases of a well-mixed and a radiatively driven STBL. Two of the simulations differ only in the ambient aerosol concentration and show its effect on cloud microphysics. The third simulation is based on the data obtained by Nicholls, and the simulation results from this case are contrasted with his measurements. Cloud-layer dynamical parameters and cloud droplet spectra are in reasonably good agreement with observations. As demonstrated by the results of three large eddy simulations presented in the paper, the cloud microphysical parameters are significantly affected by cloud dynamics. This is evidenced by the sensitivity of the cloud drop spectra itself, as well as by that of the integral parameters of the spectra, such as mean radii and droplet concentration. Experiments presented here also show that cloud microstructure is significantly asymmetric between updrafts and downdrafts. Mixing with dry air from the inversion may significantly enhance evaporation and result in cloud-free zones within the cloud. As a result of mixing, the cloud layer is very inhomogeneous, especially near its top and bottom. The authors analyze in detail the fine structure of the supersaturation field and suggest an explanation for the formation of the model-predicted supersaturation peak near the cloud top. The LES results suggest that super-saturation may have a sharp increase in near-saturated parcels that undergo forced vertical displacement at the cloud-layer top. The main forcing mechanism that may supply the additional energy for the forced convection in the case presented is from propagating gravity waves. Although radiative cooling may also result in increased convective activity at cloud top, the sensitivity tests presented here suggest that, at least in these simulations, this effect is not dominant.
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      Modeling of Stratocumulus Cloud Layers in a Large Eddy Simulation Model with Explicit Microphysics

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4157903
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    • Journal of the Atmospheric Sciences

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    contributor authorKogan, Y. L.
    contributor authorKhairoutdinov, M. P.
    contributor authorLilly, D. K.
    contributor authorKogan, Z. N.
    contributor authorLiu, Qingfu
    date accessioned2017-06-09T14:33:19Z
    date available2017-06-09T14:33:19Z
    date copyright1995/08/01
    date issued1995
    identifier issn0022-4928
    identifier otherams-21551.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4157903
    description abstractA new large eddy simulation (LES) stratocumulus cloud model with an explicit formulation of micro-physical processes has been developed, and the results from three large eddy simulations are presented to illustrate the effects of the stratocumulus-topped boundary layer (STBL) dynamics on cloud microphysical parameters. The simulations represent cases of a well-mixed and a radiatively driven STBL. Two of the simulations differ only in the ambient aerosol concentration and show its effect on cloud microphysics. The third simulation is based on the data obtained by Nicholls, and the simulation results from this case are contrasted with his measurements. Cloud-layer dynamical parameters and cloud droplet spectra are in reasonably good agreement with observations. As demonstrated by the results of three large eddy simulations presented in the paper, the cloud microphysical parameters are significantly affected by cloud dynamics. This is evidenced by the sensitivity of the cloud drop spectra itself, as well as by that of the integral parameters of the spectra, such as mean radii and droplet concentration. Experiments presented here also show that cloud microstructure is significantly asymmetric between updrafts and downdrafts. Mixing with dry air from the inversion may significantly enhance evaporation and result in cloud-free zones within the cloud. As a result of mixing, the cloud layer is very inhomogeneous, especially near its top and bottom. The authors analyze in detail the fine structure of the supersaturation field and suggest an explanation for the formation of the model-predicted supersaturation peak near the cloud top. The LES results suggest that super-saturation may have a sharp increase in near-saturated parcels that undergo forced vertical displacement at the cloud-layer top. The main forcing mechanism that may supply the additional energy for the forced convection in the case presented is from propagating gravity waves. Although radiative cooling may also result in increased convective activity at cloud top, the sensitivity tests presented here suggest that, at least in these simulations, this effect is not dominant.
    publisherAmerican Meteorological Society
    titleModeling of Stratocumulus Cloud Layers in a Large Eddy Simulation Model with Explicit Microphysics
    typeJournal Paper
    journal volume52
    journal issue16
    journal titleJournal of the Atmospheric Sciences
    identifier doi10.1175/1520-0469(1995)052<2923:MOSCLI>2.0.CO;2
    journal fristpage2923
    journal lastpage2940
    treeJournal of the Atmospheric Sciences:;1995:;Volume( 052 ):;issue: 016
    contenttypeFulltext
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    DSpace software copyright © 2002-2015  DuraSpace
    نرم افزار کتابخانه دیجیتال "دی اسپیس" فارسی شده توسط یابش برای کتابخانه های ایرانی | تماس با یابش
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