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    Nonmodal Barotropic Dynamics of the Intraseasonal Disturbances

    Source: Journal of the Atmospheric Sciences:;1995:;Volume( 052 ):;issue: 007::page 896
    Author:
    Joseph Chang, J-C.
    ,
    Mak, Mankin
    DOI: 10.1175/1520-0469(1995)052<0896:NBDOTI>2.0.CO;2
    Publisher: American Meteorological Society
    Abstract: The intraseasonal disturbances and their relation to the corresponding time-mean flows at 500 mb of nine boreal winters me investigated. The barotropic normal mode instability properties of the seasonal mean flow are found not to be indicative of the intensity of the intraseasonal variability. An application of the dynamical empirical orthogonal function (DEOF) analysis to two distinctly different seasons reveals that only a small fraction of the observed intraseasonal variance is identifiable with the unstable normal modes as individual entities. Each of the few leading DEOFs mainly consists of a slightly modified stable normal mode. The nonmodal growth of the observed intraseasonal disturbances is analyzed in the context of optimal modes with respect to the corresponding seasonal mean flows for different optimization times. The amplifying 1-day optimal structures are much more in number and have much greater growth rate than the unstable normal modes. Several narrow bands of such optimal modes are particularly prevalent. The most pronounced band has a characteristic time of about 20 days and has a localized structure over the Atlantic. The daily variation of the kinetic energy associated with all the 1-day amplifying optimal structures supports the notion that the nonmodal growth is important for the intraseasonal disturbances in winter. The evolution of all the amplifying optimal modes for a longer optimization time such as τ = 4 days over a period of τ does not describe the variation of the observed disturbances nearly as well. The synoptic-scale eddy forcing of the intraseasonal disturbances contributes significantly to the intraseasonal variability in the winter hemisphere.
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      Nonmodal Barotropic Dynamics of the Intraseasonal Disturbances

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4157750
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    contributor authorJoseph Chang, J-C.
    contributor authorMak, Mankin
    date accessioned2017-06-09T14:32:54Z
    date available2017-06-09T14:32:54Z
    date copyright1995/04/01
    date issued1995
    identifier issn0022-4928
    identifier otherams-21413.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4157750
    description abstractThe intraseasonal disturbances and their relation to the corresponding time-mean flows at 500 mb of nine boreal winters me investigated. The barotropic normal mode instability properties of the seasonal mean flow are found not to be indicative of the intensity of the intraseasonal variability. An application of the dynamical empirical orthogonal function (DEOF) analysis to two distinctly different seasons reveals that only a small fraction of the observed intraseasonal variance is identifiable with the unstable normal modes as individual entities. Each of the few leading DEOFs mainly consists of a slightly modified stable normal mode. The nonmodal growth of the observed intraseasonal disturbances is analyzed in the context of optimal modes with respect to the corresponding seasonal mean flows for different optimization times. The amplifying 1-day optimal structures are much more in number and have much greater growth rate than the unstable normal modes. Several narrow bands of such optimal modes are particularly prevalent. The most pronounced band has a characteristic time of about 20 days and has a localized structure over the Atlantic. The daily variation of the kinetic energy associated with all the 1-day amplifying optimal structures supports the notion that the nonmodal growth is important for the intraseasonal disturbances in winter. The evolution of all the amplifying optimal modes for a longer optimization time such as τ = 4 days over a period of τ does not describe the variation of the observed disturbances nearly as well. The synoptic-scale eddy forcing of the intraseasonal disturbances contributes significantly to the intraseasonal variability in the winter hemisphere.
    publisherAmerican Meteorological Society
    titleNonmodal Barotropic Dynamics of the Intraseasonal Disturbances
    typeJournal Paper
    journal volume52
    journal issue7
    journal titleJournal of the Atmospheric Sciences
    identifier doi10.1175/1520-0469(1995)052<0896:NBDOTI>2.0.CO;2
    journal fristpage896
    journal lastpage914
    treeJournal of the Atmospheric Sciences:;1995:;Volume( 052 ):;issue: 007
    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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