Assimilating host model information into a limited area model
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, Jk, measuring the distance to the large-scale vorticity...
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| Format: | Article |
| Language: | English |
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Stockholm University Press
2012-01-01
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| Series: | Tellus: Series A, Dynamic Meteorology and Oceanography |
| Subjects: | |
| Online Access: | http://www.tellusa.net/index.php/tellusa/article/view/15836/pdf |
| _version_ | 1828396253628596224 |
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| author | Nils Gustafsson Per Dahlgren |
| author_facet | Nils Gustafsson Per Dahlgren |
| author_sort | Nils Gustafsson |
| collection | DOAJ |
| description | 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, Jk, 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 Jk 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.The review process was handled by Editor-in-Cheif Harald Lejenäs |
| first_indexed | 2024-12-10T08:27:12Z |
| format | Article |
| id | doaj.art-7bd1dd73254546dc99d54ab36a13a08c |
| institution | Directory Open Access Journal |
| issn | 0280-6495 1600-0870 |
| language | English |
| last_indexed | 2024-12-10T08:27:12Z |
| publishDate | 2012-01-01 |
| publisher | Stockholm University Press |
| record_format | Article |
| series | Tellus: Series A, Dynamic Meteorology and Oceanography |
| spelling | doaj.art-7bd1dd73254546dc99d54ab36a13a08c2022-12-22T01:56:13ZengStockholm University PressTellus: Series A, Dynamic Meteorology and Oceanography0280-64951600-08702012-01-0164011710.3402/tellusa.v64i0.15836Assimilating host model information into a limited area modelNils GustafssonPer DahlgrenWe 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, Jk, 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 Jk 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.The review process was handled by Editor-in-Cheif Harald Lejenäshttp://www.tellusa.net/index.php/tellusa/article/view/15836/pdfdata-assimilationlarge-scale constrainterror covarianceslimited areahost model |
| spellingShingle | Nils Gustafsson Per Dahlgren Assimilating host model information into a limited area model Tellus: Series A, Dynamic Meteorology and Oceanography data-assimilation large-scale constraint error covariances limited area host model |
| title | Assimilating host model information into a limited area model |
| title_full | Assimilating host model information into a limited area model |
| title_fullStr | Assimilating host model information into a limited area model |
| title_full_unstemmed | Assimilating host model information into a limited area model |
| title_short | Assimilating host model information into a limited area model |
| title_sort | assimilating host model information into a limited area model |
| topic | data-assimilation large-scale constraint error covariances limited area host model |
| url | http://www.tellusa.net/index.php/tellusa/article/view/15836/pdf |
| work_keys_str_mv | AT nilsgustafsson assimilatinghostmodelinformationintoalimitedareamodel AT perdahlgren assimilatinghostmodelinformationintoalimitedareamodel |