The ALERMO model which is the acronym for the Aegean and Levantine Eddy Resolving MOdel (Korres and Lascaratos, 2003) consists of a high-resolution implementation of the Princeton ocean model (Blumberg and Mellor, 1987). It has been developed within the framework of the Mediterranean Forecasting System Pilot Project – MFSPP (Pinardi et al., 2003) aiming in preparing the prerequisites for operational oceanography of the Mediterranean Sea. In MFSPP the ALERMO model had a 1/20^o of horizontal resolution and it was one-way nested with a 1/8^o × 1/8^o global Mediterranean OGCM model (MOM).

An upgraded version of the ALERMO model with a 1/30^o of horizontal resolution was developed within the framework of MFSTEP (Mediterranean Forecasting System - Towards Environmental Predictions). ALERMO is one-way nested to a global Mediterranean OGCM (MOM, 1/16^o × 1/16^o) running operationally on a daily basis.

Upgraded ALERMO model characteristics in MFSTEP

Model code: Princeton Ocean Model (POM)

Geographical area covered: 20^oE – 36.4^oE & 30.7^oN – 41.2^oN

Horizontal resolution: 1/30^o × 1/30^o

Vertical resolution: 25 sigma levels logarithmically distributed

Advection of tracers: Smolarkiewicz upstream scheme with anti-diffusive velocities

Open boundary conditions: One-way nesting with the 1/16^o × 1/16^o MFSTEP Mediterranean OGCM model running operationally. The nesting scheme has been developed within MFSPP and is based on:

- Flathers (1975) open boundary conditions for nesting of the barotropic velocities normal to the open boundaries

- Volume conservation at the open boundaries

- Direct specification of baroclinic velocities, free surface elevation and tangential barotropic velocities

- Direct specification of tracers (T/S) in case of inflow and upstream advection in the case of outflow

Dardanelles inflow/outflow: The present version treats Dardanelles as an open boundary where the net volume inflow into the Aegean Sea, the interface depth and the salinity of the inflowing waters are specified. Such a change was motivated by the fact that the old parameterization was underestimating the freshwater input of Black Sea origin into the Aegean Sea.

Atmospheric coupling: ALERMO is one-way coupled with the SKIRON weather forecasting system (LAM).

The SKIRON system provides:

· Air temperature and relative humidity at 2m above sea surface

· Wind velocity at 10m above sea surface

· Sea level atmospheric pressure

· Net shortwave radiation at the sea surface

· Downward longwave radiation

· Precipitation rate

Momentum fluxes, evaporative, upward longwave radiation and sensible heat fluxes are calculated through bulk formulae using the SST predicted by the ALERMO model.

Furthermore the upgraded version of the ALERMO model provides the atmospheric pressure loading and optional inclusion of tidal forcing

Surface freshwater flux: Real freshwater flux instead of (virtual) salt flux is used for the sea surface boundary conditions

Variational Initialization: The ALERMO model will be initialized from the MFSTEP OGCM on a weakly basis (operationally during the TOP period) using the Variational Initialization (VI) method (Auclair et al. 2000).

Data assimilation: An optimal interpolation scheme (O.I. MARK-II) will be implemented in the near future.

References

Auclair F., Casitas, S., Marsaleix, P., 2000. Application of an inverse method to coastal modeling. J. Atmos. Oceanic Technol., 17, 1368-1391.

Blumberg A., and G. L. Mellor, 1987: A description of a three-dimensional coastal ocean circulation model. In Three-Dimensional Coastal Ocean Models, N. S. Heaps (Ed.), 1-16, American Geophysical Union, Washington, DC.

Korres, G., and A.Lascaratos, 2003: An eddy resolving model of the Aegean and Levantine basins for the Mediterranean Forecasting System Pilot Project (MFSPP) : Implementation and climatological runs. Analles Geophysicae, 21, 205-220.

Kallos, G. and co-authors, 1997: The regional weather forecasting system SKIRON: an overview. Proceedings of the symposium on regional weather prediction on parallel computer environments, University of Athens.

Lascaratos, A. and K. Nittis, 1998: A high-resolution three-dimensional numerical study of intermediate water formation in the Levantine Sea. J. Geophys. Res., 103 (C9) 18497-18511.

Pinardi, N., Allen, I., Demirov, E., De Mey, P., Korres, G., Lascaratos, A., Le Traon, P-Y., Maillard, C., Manzella G., and Tziavos, C., 2003: The Mediterranean Ocean Forecasting System: First phase of implementation (1998-2001). Analles Geophysicae, 21, 3-20.