Assimilation of ocean colour data into a Biogeochemical Flux Model of the Eastern Mediterranean Sea

Abstract

Abstract. 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-ofview 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. Results, however, suggest the need of subsurface data to enhance the estimation of the ecosystem variables in the deep layers.

Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research

“…11) model were used to study the ecosystem functioning in more detail, although mostly on the regional scale, addressing the dynamics of the microbial loop, the bacterial dynamic and primary production (Allen et al, 1998;Anderson and Turley, 2003;Polimene et al, 2007;Lazzari et al, 2012). A significant effort has focused on the data assimilation of biophysical parameters into an ecosystem model of the eastern Mediterranean (Triantafyllou et al, 2005(Triantafyllou et al, , 2007.…”

“…The surface and deep chlorophyll maxima formed near the base of the euphotic zone depend on light and biochemical variability imposed by FZFEs (Yılmaz et al, 1994;Yacobi et al, 1995;Ediger et al, 1996Ediger et al, , 2005. In some Mediterranean areas FZFEs affect the distribution of plankton biomass and community composition either directly, due to the physical characteristics (e.g., salinity and temperature boundaries, convergence or divergence processes), or indirectly, through the influence on the chemical parameters (Fiala et al, 1994;Van Wambeke et al, 2004;Riandey et al, 2005;Siokou-Frangou et al, 2009, among others). Recently, relatively high concentrations of biogenic silica were found in some areas, perhaps related to the presence of eddies (Crombet et al, 2011).…”

The Mediterranean Ocean Colour Observing System – system development and product validation

“…are already convincing examples of their assimilation in biogeochemical models (Natvik and Evensen, 2003;Triantafyllou et al, 2007). Therefore, the access to long-term, continuous and near real-time OC satellite data is considered one of the requirements of the new operational ocean observing and forecasting systems, currently being developed at global and regional scales.…”

Preface "Operational oceanography in the Mediterranean Sea: the second stage of development"

“…Moreover data assimilation of chlorophyll data has been studied (Crispi et al, 2006) and proven to be effective in a large scale biochemical model implementation in the Eastern Mediterranean Sea (Triantafyllou et al, 2007). MFSTEP has put the scientific basis for the future forecasting models of marine biochemistry that are now working in real time.…”