EurOCEAN 2000 - Vlaams Instituut voor de Zee

allows the research community to fast communicate with the data acquisition systems and it
can generate easily multiple users of the data itself as recommended by Molinari (1999).
OCEAN MODELLING FOR FORECASTING AT THE BASIN SCALE
AND IN THE SHELF AREAS
The past ten years the Mediterranean research community has developed a suite of OGCM and
regional models capable of simulating the seasonal and interannual variability of the basin
currents with good accuracy (Korres et al., 2000). The forecasting OGCM is at 1/8 X 1/8degree
resolution and 31 vertical levels and the assimilation/forecasting system is composed of
four parts:
1. The first consists of an assimilation engine partially developed in the project (DeMey and
Benkiran, 2000) which uses a reduced order Optimal Interpolation scheme with empirical
orthogonal functions used to project in an assimilation subspace. The assimilation engine is
used for both sea level anomalies and XBT with multivariate empirical functions. In
practice, sea level anomaly is assimilated to give the first guess for the successive
multivariate assimilation of temperature profiles from XBT. Thus the two data sets are
assimilated sequentially. Both sea level anomaly and temperature profiles assimilation is
multivariate but the sequential assimilation allows the usage of different empirical
orthogonal functions that are optimized for the two different data sets.
2. The second is a software interface between the atmospheric forcing parameters and the
OGCM. This interface allows to drive the ocean model every week from the previous week
forecasting day (J0-7) to the present week starting forecast day (J0) with atmospheric
analyses (hindcast mode). Then the same interface couples the OGCM with ten days
deterministic forecast surface parameters from the ECMWF (European Center for Medium
range Weather Forecast, forecast mode). The sea surface temperature data from satellite are
used in the hindcast run to correct the surface heat fluxes by means of a flux correction term
3. The third part is a software interface between the observed data and the assimilation engine,
to feed the observations in the appropriate format to the model.
4. The fourth part is a post processing interface that translates the model forecast to image
products for Web publication and dissemination of information.
The whole system is represented schematically in Fig.2
The OGCM simulations are also used to initialize regional and shelf models that receive
boundary fields at different time frequencies. The downscaling brings the OGCM 12.5 km
resolution fields down to 1-2 km resolution in the shelf areas. This is at the base of the coastal
forecasting system of the next phase, where the initialization of the regional and shelf models
will crucially depend upon the OGCM dynamical fields. The Mediterranean Sea shelf area is
narrow and the general circulation can determine a large portion of the coastal hydrodynamics
variability. Thus two and three fold nesting is necessary to develop the future experiments of
near real time forecasting in the coastal areas.
Finally, ecosystem models are also implemented and validated during MFSPP at several
coastal test sites. The aim is to calibrate the ecosystem model parameters in a one dimensional
set up since it has been found that this is useful to understand non generic model parameters. In
the next phase, it is hoped to start the simulations of the ecosystem variability with a fully
coupled 3-D ecosystem model based upon the shelf models developed in MFSPP.
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