Four-dimensional variational data assimilation for a limited area model

A 4-dimensional variational data assimilation (4D-Var) scheme for the HIgh Resolution Limited Area Model (HIRLAM) forecasting system is described in this article. The innovative approaches to the multi-incremental formulation, the weak digital filter constraint and the semi-Lagrangian time integration are highlighted with some details. The implicit dynamical structure functions are discussed using single observation experiments, and the sensitivity to various parameters of the 4D-Var formulation is illustrated. To assess the meteorological impact of HIRLAM 4D-Var, data assimilation experiments for five periods of 1 month each were performed, using HIRLAM 3D-Var as a reference. It is shown that the HIRLAM 4D-Var consistently out-performs the HIRLAM 3D-Var, in particular for cases with strong mesoscale storm developments. The computational performance of the HIRLAM 4D-Var is also discussed.

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Copyright 2012 Author(s). Published under license by Wiley-Blackwell.
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Author Gustafsson, N.
Huang, Xiang-Yu
Yang, X.
Mogensen, K.
Lindskog, M.
Vignes, O.
Wilhelmsson, T.
Thorsteinsson, S.
Publisher UCAR/NCAR - Library
Publication Date 2012-02-01T00:00:00
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Topic Category geoscientificInformation
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Metadata Date 2025-07-15T21:37:45.995742
Metadata Record Identifier edu.ucar.opensky::articles:11684
Metadata Language eng; USA
Suggested Citation Gustafsson, N., Huang, Xiang-Yu, Yang, X., Mogensen, K., Lindskog, M., Vignes, O., Wilhelmsson, T., Thorsteinsson, S.. (2012). Four-dimensional variational data assimilation for a limited area model. UCAR/NCAR - Library. https://n2t.org/ark:/85065/d7gf0v43. Accessed 23 August 2025.

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