Article (Scientific journals)
Comparison of different incremental analysis update schemes in a realistic assimilation system with Ensemble Kalman Filter
Yan, Yajing; Barth, Alexander; Beckers, Jean-Marie et al.
2017In Ocean Modelling, 115, p. 27-41
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Keywords :
Comparison; Ensemble Kalman Filter; Incremental analysis update; Probabilistic metrics; Bandpass filters; Integration; Continuous ranked probability scores; Ensemble forecast systems; Equilibrium modeling; Incremental analysis; North Atlantic Ocean; Kalman filters; Kalman filter; Atlantic Ocean; Atlantic Ocean (North)
Abstract :
[en] In this paper, three incremental analysis update schemes (IAU 0, IAU 50 and IAU 100) are compared in the same assimilation experiments with a realistic eddy permitting primitive equation model of the North Atlantic Ocean using the Ensemble Kalman Filter. The difference between the three IAU schemes lies on the position of the increment update window. The relevance of each IAU scheme is evaluated through analyses on both thermohaline and dynamical variables. The validation of the assimilation results is performed according to both deterministic and probabilistic metrics against different sources of observations. For deterministic validation, the ensemble mean and the ensemble spread are compared to the observations. For probabilistic validation, the continuous ranked probability score (CRPS) is used to evaluate the ensemble forecast system according to reliability and resolution. The reliability is further decomposed into bias and dispersion by the reduced centred random variable (RCRV) score. The obtained results show that 1) the IAU 50 scheme has the same performance as the IAU 100 scheme 2) the IAU 50/100 schemes outperform the IAU 0 scheme in error covariance propagation for thermohaline variables in relatively stable region, while the IAU 0 scheme outperforms the IAU 50/100 schemes in dynamical variables estimation in dynamically active region 3) in case with sufficient number of observations and good error specification, the impact of IAU schemes is negligible. The differences between the IAU 0 scheme and the IAU 50/100 schemes are mainly due to different model integration time and different instability (density inversion, large vertical velocity, etc.) induced by the increment update. The longer model integration time with the IAU 50/100 schemes, especially the free model integration, on one hand, allows for better re-establishment of the equilibrium model state, on the other hand, smooths the strong gradients in dynamically active region. © 2017 Elsevier Ltd
Research center :
GHER
Disciplines :
Earth sciences & physical geography
Author, co-author :
Yan, Yajing
Barth, Alexander  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > GeoHydrodynamics and Environment Research (GHER)
Beckers, Jean-Marie  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > GeoHydrodynamics and Environment Research (GHER)
Brankart, J. M.;  CNRS LGGE, Université de Grenoble 1, Grenoble, France
Brasseur, P.;  CNRS LGGE, Université de Grenoble 1, Grenoble, France
Candille, G.;  CNRS LGGE, Université de Grenoble 1, Grenoble, France
Language :
English
Title :
Comparison of different incremental analysis update schemes in a realistic assimilation system with Ensemble Kalman Filter
Publication date :
2017
Journal title :
Ocean Modelling
ISSN :
1463-5003
eISSN :
1463-5011
Publisher :
Elsevier Ltd
Volume :
115
Pages :
27-41
Peer reviewed :
Peer Reviewed verified by ORBi
European Projects :
FP7 - 283580 - SANGOMA - Stochastic Assimilation for the Next Generation Ocean Model Applications
Funders :
EU - European Commission
CE - Commission Européenne [BE]
Available on ORBi :
since 01 February 2019

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