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    Contributions to the Implementation of the Arakawa-Schubert Cumulus Parameterization in the GLA GCM

    Source: Journal of the Atmospheric Sciences:;1991:;Volume( 048 ):;issue: 013::page 1573
    Author:
    Sud, Y. C.
    ,
    Chao, Winston C.
    ,
    Walker, G. K.
    DOI: 10.1175/1520-0469(1991)048<1573:CTTIOT>2.0.CO;2
    Publisher: American Meteorological Society
    Abstract: Several integrations were made with a coarse (4° ? 5° nine-sigma level) version of the GLA GCM, which has the Arakawa?Schubert cumulus parameterization, predicted fractional cloud cover, and a parameterization of evaporation of falling rainfall. All model simulation experiments started from the ECMWF analysis for 15 December 1982 and were integrated until 31 January 1983 using climatological boundary conditions. The first ten days of model integrations show that the model-simulated tropics dries and warms as a result of excessive precipitation. Three types of model development-cum-analysis studies were made with the cumulus scheme. First, the Critical Cloud Work Function (CCWF) dataset for different sigma layers were reworked using the Cloud Work Function (CWF) database of Lord et al. as representative of time-average CWF and not the actual CCWF values as in the Arakawa?Schubert implementation of cumulus convection. The experiments with the new CCWF dataset helped to delineate the influence of changing CCWF on model simulations. Larger values of CCWF partially alleviated the problem of excessive heating and drying during spinup and sharpened the tropical ITCZ (Intertropical Convergence Zone). Second, by comparing two simulations, one with and one without cumulus convection, the role of cumulus convection in maintaining the observed tropical rainfall and 850 mb easterly winds is clarified. Third, by using Simpson's relations between cloud radii and cumulus entrainment parameter, ?, in the Arakawa?Schubert cumulus scheme, realistic upper and lower bounds on ? were obtained. This improvement had a significant impact on the time evolution of tropical temperature and humidity simulation. It also significantly suppressed the excessive rainfall during spinup. Finally, by invoking ?min = 0.0002 m?1 (Rmax = 1.00 km) another simulation was made. In this simulation, not only the excessive initial rainfall was virtually eliminated, but a more realistic vertical distribution of specific humidity in the tropics was produced. Despite the conceptual simplicity of the latter, it has made some very significant improvement to the monthly simulation in the tropics.
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      Contributions to the Implementation of the Arakawa-Schubert Cumulus Parameterization in the GLA GCM

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4156804
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    contributor authorSud, Y. C.
    contributor authorChao, Winston C.
    contributor authorWalker, G. K.
    date accessioned2017-06-09T14:30:27Z
    date available2017-06-09T14:30:27Z
    date copyright1991/07/01
    date issued1991
    identifier issn0022-4928
    identifier otherams-20562.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4156804
    description abstractSeveral integrations were made with a coarse (4° ? 5° nine-sigma level) version of the GLA GCM, which has the Arakawa?Schubert cumulus parameterization, predicted fractional cloud cover, and a parameterization of evaporation of falling rainfall. All model simulation experiments started from the ECMWF analysis for 15 December 1982 and were integrated until 31 January 1983 using climatological boundary conditions. The first ten days of model integrations show that the model-simulated tropics dries and warms as a result of excessive precipitation. Three types of model development-cum-analysis studies were made with the cumulus scheme. First, the Critical Cloud Work Function (CCWF) dataset for different sigma layers were reworked using the Cloud Work Function (CWF) database of Lord et al. as representative of time-average CWF and not the actual CCWF values as in the Arakawa?Schubert implementation of cumulus convection. The experiments with the new CCWF dataset helped to delineate the influence of changing CCWF on model simulations. Larger values of CCWF partially alleviated the problem of excessive heating and drying during spinup and sharpened the tropical ITCZ (Intertropical Convergence Zone). Second, by comparing two simulations, one with and one without cumulus convection, the role of cumulus convection in maintaining the observed tropical rainfall and 850 mb easterly winds is clarified. Third, by using Simpson's relations between cloud radii and cumulus entrainment parameter, ?, in the Arakawa?Schubert cumulus scheme, realistic upper and lower bounds on ? were obtained. This improvement had a significant impact on the time evolution of tropical temperature and humidity simulation. It also significantly suppressed the excessive rainfall during spinup. Finally, by invoking ?min = 0.0002 m?1 (Rmax = 1.00 km) another simulation was made. In this simulation, not only the excessive initial rainfall was virtually eliminated, but a more realistic vertical distribution of specific humidity in the tropics was produced. Despite the conceptual simplicity of the latter, it has made some very significant improvement to the monthly simulation in the tropics.
    publisherAmerican Meteorological Society
    titleContributions to the Implementation of the Arakawa-Schubert Cumulus Parameterization in the GLA GCM
    typeJournal Paper
    journal volume48
    journal issue13
    journal titleJournal of the Atmospheric Sciences
    identifier doi10.1175/1520-0469(1991)048<1573:CTTIOT>2.0.CO;2
    journal fristpage1573
    journal lastpage1586
    treeJournal of the Atmospheric Sciences:;1991:;Volume( 048 ):;issue: 013
    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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