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    A Low-Order Model Investigation of the Analysis of Gravity Waves in the Ensemble Kalman Filter

    Source: Journal of the Atmospheric Sciences:;2009:;Volume( 066 ):;issue: 006::page 1717
    Author:
    Neef, Lisa J.
    ,
    Polavarapu, Saroja M.
    ,
    Shepherd, Theodore G.
    DOI: 10.1175/2008JAS2585.1
    Publisher: American Meteorological Society
    Abstract: The behavior of the ensemble Kalman filter (EnKF) is examined in the context of a model that exhibits a nonlinear chaotic (slow) vortical mode coupled to a linear (fast) gravity wave of a given amplitude and frequency. It is shown that accurate recovery of both modes is enhanced when covariances between fast and slow normal-mode variables (which reflect the slaving relations inherent in balanced dynamics) are modeled correctly. More ensemble members are needed to recover the fast, linear gravity wave than the slow, vortical motion. Although the EnKF tends to diverge in the analysis of the gravity wave, the filter divergence is stable and does not lead to a great loss of accuracy. Consequently, provided the ensemble is large enough and observations are made that reflect both time scales, the EnKF is able to recover both time scales more accurately than optimal interpolation (OI), which uses a static error covariance matrix. For OI it is also found to be problematic to observe the state at a frequency that is a subharmonic of the gravity wave frequency, a problem that is in part overcome by the EnKF. However, error in the modeled gravity wave parameters can be detrimental to the performance of the EnKF and remove its implied advantages, suggesting that a modified algorithm or a method for accounting for model error is needed.
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      A Low-Order Model Investigation of the Analysis of Gravity Waves in the Ensemble Kalman Filter

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4208143
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    contributor authorNeef, Lisa J.
    contributor authorPolavarapu, Saroja M.
    contributor authorShepherd, Theodore G.
    date accessioned2017-06-09T16:22:44Z
    date available2017-06-09T16:22:44Z
    date copyright2009/06/01
    date issued2009
    identifier issn0022-4928
    identifier otherams-66771.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4208143
    description abstractThe behavior of the ensemble Kalman filter (EnKF) is examined in the context of a model that exhibits a nonlinear chaotic (slow) vortical mode coupled to a linear (fast) gravity wave of a given amplitude and frequency. It is shown that accurate recovery of both modes is enhanced when covariances between fast and slow normal-mode variables (which reflect the slaving relations inherent in balanced dynamics) are modeled correctly. More ensemble members are needed to recover the fast, linear gravity wave than the slow, vortical motion. Although the EnKF tends to diverge in the analysis of the gravity wave, the filter divergence is stable and does not lead to a great loss of accuracy. Consequently, provided the ensemble is large enough and observations are made that reflect both time scales, the EnKF is able to recover both time scales more accurately than optimal interpolation (OI), which uses a static error covariance matrix. For OI it is also found to be problematic to observe the state at a frequency that is a subharmonic of the gravity wave frequency, a problem that is in part overcome by the EnKF. However, error in the modeled gravity wave parameters can be detrimental to the performance of the EnKF and remove its implied advantages, suggesting that a modified algorithm or a method for accounting for model error is needed.
    publisherAmerican Meteorological Society
    titleA Low-Order Model Investigation of the Analysis of Gravity Waves in the Ensemble Kalman Filter
    typeJournal Paper
    journal volume66
    journal issue6
    journal titleJournal of the Atmospheric Sciences
    identifier doi10.1175/2008JAS2585.1
    journal fristpage1717
    journal lastpage1734
    treeJournal of the Atmospheric Sciences:;2009:;Volume( 066 ):;issue: 006
    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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