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Original Research Papers

A comparative study of 4D-VAR and a 4D Ensemble Kalman Filter: perfect model simulations with Lorenz-96

Authors:

Elana J. Fertig ,

Institute for Physical Science and Technology and Department of Mathematics, University of Maryland, College Park, MD 20742, US
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John Harlim,

Institute for Physical Science and Technology and Department of Mathematics, University of Maryland, College Park, MD 20742, US
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Brian R. Hunt

Institute for Physical Science and Technology and Department of Mathematics, University of Maryland, College Park, MD 20742, US
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Abstract

We formulate a four-dimensional Ensemble Kalman Filter (4D-LETKF) that minimizes a cost function similar to that in a 4D-VAR method. Using perfect model experiments with the Lorenz-96 model, we compare assimilation of simulated asynchronous observations with 4D-VAR and 4D-LETKF. We find that both schemes have comparable error when 4D-LETKF is performed sufficiently frequently and when 4D-VAR is performed over a sufficiently long analysis time window.We explore how the error depends on the time between analyses for 4D-LETKF and the analysis time window for 4D-VAR.

How to Cite: Fertig, E.J., Harlim, J. and Hunt, B.R., 2007. A comparative study of 4D-VAR and a 4D Ensemble Kalman Filter: perfect model simulations with Lorenz-96. Tellus A: Dynamic Meteorology and Oceanography, 59(1), pp.96–100. DOI: http://doi.org/10.1111/j.1600-0870.2006.00205.x
  Published on 01 Jan 2007
 Accepted on 22 Aug 2006            Submitted on 7 Jun 2006

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