A hybrid variational-ensemble data assimilation scheme with systematic error correction for limited-area ocean models
A hybrid variational-ensemble data assimilation scheme to estimate the vertical and horizontal parts of the background error covariance matrix for an ocean variational data assimilation system is presented and tested in a limited-area ocean model implemented in the western Mediterranean Sea. An exte...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2016-10-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/12/1137/2016/os-12-1137-2016.pdf |
| _version_ | 1830275119501541376 |
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| author | P. Oddo A. Storto S. Dobricic A. Russo C. Lewis R. Onken E. Coelho |
| author_facet | P. Oddo A. Storto S. Dobricic A. Russo C. Lewis R. Onken E. Coelho |
| author_sort | P. Oddo |
| collection | DOAJ |
| description | A hybrid variational-ensemble data assimilation scheme to estimate the
vertical and horizontal parts of the background error covariance matrix for
an ocean variational data assimilation system is presented and tested in a
limited-area ocean model implemented in the western Mediterranean Sea. An
extensive data set collected during the Recognized Environmental Picture
Experiments conducted in June 2014 by the Centre for Maritime Research and
Experimentation has been used for assimilation and validation. The hybrid
scheme is used to both correct the systematic error introduced in the system
from the external forcing (initialisation, lateral and surface open boundary
conditions) and model parameterisation, and improve the representation of
small-scale errors in the background error covariance matrix. An ensemble
system is run offline for further use in the hybrid scheme, generated through
perturbation of assimilated observations. Results of four different
experiments have been compared. The reference experiment uses the classical
stationary formulation of the background error covariance matrix and has no
systematic error correction. The other three experiments account for, or not,
systematic error correction and hybrid background error covariance matrix
combining the static and the ensemble-derived errors of the day. Results show
that the hybrid scheme when used in conjunction with the systematic error
correction reduces the mean absolute error of temperature and salinity misfit
by 55 and 42 % respectively, versus statistics arising from standard
climatological covariances without systematic error correction. |
| first_indexed | 2024-12-19T00:19:07Z |
| format | Article |
| id | doaj.art-b5b29cd220af43d599c387774b1e6326 |
| institution | Directory Open Access Journal |
| issn | 1812-0784 1812-0792 |
| language | English |
| last_indexed | 2024-12-19T00:19:07Z |
| publishDate | 2016-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Ocean Science |
| spelling | doaj.art-b5b29cd220af43d599c387774b1e63262022-12-21T20:45:38ZengCopernicus PublicationsOcean Science1812-07841812-07922016-10-011251137115310.5194/os-12-1137-2016A hybrid variational-ensemble data assimilation scheme with systematic error correction for limited-area ocean modelsP. Oddo0A. Storto1S. Dobricic2A. Russo3C. Lewis4R. Onken5E. Coelho6NATO Science and Technology Organization, Centre for Maritime Research and Experimentation, Viale San Bartolomeo 400, 19126 La Spezia, ItalyEuro-Mediterranean Centre for Climate Change (CMCC), via Franceschini 31, 40128 Bologna, ItalyEuropean Commission, Joint Research Centre, Via Enrico Fermi 2749, 21027 Ispra (VA), ItalyNATO Science and Technology Organization, Centre for Maritime Research and Experimentation, Viale San Bartolomeo 400, 19126 La Spezia, ItalyNATO Science and Technology Organization, Centre for Maritime Research and Experimentation, Viale San Bartolomeo 400, 19126 La Spezia, ItalyNATO Science and Technology Organization, Centre for Maritime Research and Experimentation, Viale San Bartolomeo 400, 19126 La Spezia, ItalyNATO Science and Technology Organization, Centre for Maritime Research and Experimentation, Viale San Bartolomeo 400, 19126 La Spezia, ItalyA hybrid variational-ensemble data assimilation scheme to estimate the vertical and horizontal parts of the background error covariance matrix for an ocean variational data assimilation system is presented and tested in a limited-area ocean model implemented in the western Mediterranean Sea. An extensive data set collected during the Recognized Environmental Picture Experiments conducted in June 2014 by the Centre for Maritime Research and Experimentation has been used for assimilation and validation. The hybrid scheme is used to both correct the systematic error introduced in the system from the external forcing (initialisation, lateral and surface open boundary conditions) and model parameterisation, and improve the representation of small-scale errors in the background error covariance matrix. An ensemble system is run offline for further use in the hybrid scheme, generated through perturbation of assimilated observations. Results of four different experiments have been compared. The reference experiment uses the classical stationary formulation of the background error covariance matrix and has no systematic error correction. The other three experiments account for, or not, systematic error correction and hybrid background error covariance matrix combining the static and the ensemble-derived errors of the day. Results show that the hybrid scheme when used in conjunction with the systematic error correction reduces the mean absolute error of temperature and salinity misfit by 55 and 42 % respectively, versus statistics arising from standard climatological covariances without systematic error correction.http://www.ocean-sci.net/12/1137/2016/os-12-1137-2016.pdf |
| spellingShingle | P. Oddo A. Storto S. Dobricic A. Russo C. Lewis R. Onken E. Coelho A hybrid variational-ensemble data assimilation scheme with systematic error correction for limited-area ocean models Ocean Science |
| title | A hybrid variational-ensemble data assimilation scheme with systematic error
correction for limited-area ocean models |
| title_full | A hybrid variational-ensemble data assimilation scheme with systematic error
correction for limited-area ocean models |
| title_fullStr | A hybrid variational-ensemble data assimilation scheme with systematic error
correction for limited-area ocean models |
| title_full_unstemmed | A hybrid variational-ensemble data assimilation scheme with systematic error
correction for limited-area ocean models |
| title_short | A hybrid variational-ensemble data assimilation scheme with systematic error
correction for limited-area ocean models |
| title_sort | hybrid variational ensemble data assimilation scheme with systematic error correction for limited area ocean models |
| url | http://www.ocean-sci.net/12/1137/2016/os-12-1137-2016.pdf |
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