Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
Articles
Optimal Localization for Ensemble Kalman Filter Systems
África PERIÁÑEZHendrik REICHRoland POTTHAST
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2014 Volume 92 Issue 6 Pages 585-597

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Abstract

 In ensemble Kalman filter methods, localization is applied for both avoiding the spurious correlations of distant observations and increasing the effective size of the ensemble space. The procedure is essential in order to provide quality assimilation in large systems; however a severe localization can cause imbalances that impact negatively on the accuracy of the analysis.
 We want to understand the fundamental properties of localized ensemble methods and to investigate an optimal localization expression which minimizes the analysis error. The novel analytical expression derived in this work depends on the observation error, the density of measurements, and the approximation error, i.e., the error that comes from working in the ensemble space. The mathematical results are tested with two numerical simulations using a toy model. We demonstrate that observations with different observation error or density need different localization length scales.

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© 2014 by Meteorological Society of Japan
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