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Assimilating host model information into a limited area model
SMHI, Research Department, Meteorology.
SMHI, Research Department, Meteorology.ORCID iD: 0000-0001-8376-2729
2012 (English)In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 64, 15836Article in journal (Refereed) Published
Abstract [en]

We propose to add an extra source of information to the data-assimilation of the regional HIgh Resolution Limited Area Model (HIRLAM) model, constraining larger scales to the host model providing the lateral boundary conditions. An extra term, J(k), measuring the distance to the large-scale vorticity of the host model, is added to the cost-function of the variational data-assimilation. Vorticity is chosen because it is a good representative of the large-scale flow and because vorticity is a basic control variable of the HIRLAM variational data-assimilation. Furthermore, by choosing only vorticity, the remaining model variables, divergence, temperature, surface pressure and specific humidity will be allowed to adapt to the modified vorticity field in accordance with the internal balance constraints of the regional model. The error characteristics of the J(k) term are described by the horizontal spectral densities and the vertical eigenmodes (eigenvectors and eigenvalues) of the host model vorticity forecast error fields, expressed in the regional model geometry. The vorticity field, provided by the European Centre for Medium-range Weather Forecasts (ECMWF) operational model, was assimilated into the HIRLAM model during an experiment period of 33 d in winter with positive impact on forecast verification statistics for upper air variables and mean sea level pressure.

Place, publisher, year, edition, pages
2012. Vol. 64, 15836
Keyword [en]
data-assimilation, large-scale constraint, error covariances, limited area, host model
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:smhi:diva-489DOI: 10.3402/tellusa.v64i0.15836ISI: 000300394900001OAI: oai:DiVA.org:smhi-489DiVA: diva2:805005
Available from: 2015-04-14 Created: 2015-04-14 Last updated: 2016-11-21Bibliographically approved

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