The ETKF rescaling scheme in HIRLAM
2011 (English)In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 63, no 3, 385-401 p.Article in journal (Refereed) Published
The ETKF rescaling scheme has been implemented into the HIRLAM forecasting system in order to estimate the uncertainty of the model state. The main purpose is to utilize this uncertainty information for modelling of flow-dependent background error covariances within the framework of a hybrid variational ensemble data assimilation scheme. The effects of rank-deficiency in the ETKF formulation is explained and the need for variance inflation as a way to compensate for these effects is justified. A filter spin-up algorithm is proposed as a refinement of the variance inflation. The proposed spin-up algorithm will also act to prevent ensemble collapse since the ensemble will receive 'fresh blood' in the form of additional perturbation components, generated on the basis of a static background error covariance matrix. The resulting ETKF-based ensemble perturbations are compared with ensemble perturbations based on targeted singular vectors and are shown to have more realistic spectral characteristics.
Place, publisher, year, edition, pages
2011. Vol. 63, no 3, 385-401 p.
Meteorology and Atmospheric Sciences
Research subject Meteorology
IdentifiersURN: urn:nbn:se:smhi:diva-526DOI: 10.1111/j.1600-0870.2011.00513.xISI: 000289481700003OAI: oai:DiVA.org:smhi-526DiVA: diva2:805746