Ocean Science www.ocean-sci.net 1812-0784 1812-0792 3 3 2007 10.5194/os-3-397-2007 http://www.ocean-sci.net/3/397/2007/ http://www.ocean-sci.net/3/397/2007/os-3-397-2007.html http://www.ocean-sci.net/3/397/2007/os-3-397-2007.pdf 397 410 2007-08-21 Assimilation of ocean colour data into a Biogeochemical Flux Model of the Eastern Mediterranean Sea G. Triantafyllou gt@ath.hcmr.gr G. Korres I. Hoteit G. Petihakis A. C. Banks Hellenic Centre for Marine Research, Anavissos, Greece Scripps Institution of Oceanography, La Jolla, CA, USA An advanced multivariate sequential data assimilation system has been implemented within the framework of the European MFSTEP project to fit a three-dimensional biogeochemical model of the Eastern Mediterranean to satellite chlorophyll data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). The physics are described by the Princeton Ocean Model (POM) while the biochemistry of the ecosystem is tackled with the Biogeochemical Flux Model (BFM). The assimilation scheme is based on the Singular Evolutive Extended Kalman (SEEK) filter, in which the error statistics were parameterized by means of a suitable set of Empirical Orthogonal Functions (EOFs). To avoid spurious long-range correlations associated with the limited number of EOFs, the filter covariance matrix was given compact support through a radius of influence around every data point location. Hindcast experiments were performed for one year over 1999 and forced with ECMWF 6 h atmospheric fields. The solution of the assimilation system was evaluated against the assimilated data and the MedAtlas climatology, and by assessing the impact of the assimilation on non-observed biogeochemical processes. It is found that the assimilation of SeaWiFS data improves the overall behavior of the BFM model and efficiently removes long term biases from the model despite some difficulties during the spring bloom period. 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