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MEDITERRANEAN EDDY RESOLVING MODELLING AND INTERDISCIPLINARY STUDIES

Objective

The aims of this study can be summarised as follows: 1) The realistic simulation of the mesoscale variability on seasonal time scales with a primitive equation Eddy resolving General Circulation Model (EGCM) of the whole Mediterranean basin. The model will include up to date air-sea exchange physical parameterizations and turbulent closure schemes for vertical mixing. 2) The simulation of the interannual and seasonal Levantine Intermediate Water (LIW) and Deep Water (DW) formation rates and their spatial distribution. 3) The understanding of the vorticity dynamics in the basin via quasi-geostrophic simulations of the wind driven circulation and the definition of the sources of the mesoscale field in the overall basin. 4) The calculation of the renewal time of the intermediate and deep water masses based upon a transient tracer data set and the implementation of these data into the EGCM. 5) The description of the Aegean basin circulation variability from hydrological data analysis and the development of a subregional model coupled with the EGCM. 6) The description of the Adriatic sea thermohaline circulation as given by the EGCM simulations and by chemical and hydrological data sets analysis.
A general circulation model (GCM) has been set up in the Mediterranean basin. The novelty of the Mediterranean application consists of the air sea parameterizations package entirely developed and calibrated for the Mediterranean Sea. The package allows the calculation of the heat and momentum budget at the air sea interface by applying raw atmospheric parameters (air temperature, wind velocity and relative humidity) and transforming them into model interactive fluxes by means of bulk parameterization formulae. The major scientific results are concerned with the definition of the characteristics of the seasonal cycle in the Mediterranean general circulation. The spatial scales of the barotropic and baroclinic circulation consist of subbasin scale gyres together with a complicated system of intensified currents, both in open ocean and lateral boundary areas. The interannual general circulation scale variability is connected with the location, shape and strength of the subbasin gyres, some of them started by the anomalous heat and wind events in the atmosphere. Winter and summer anomalies can induce new gyres which have a life time longer than the atmospheric anomaly which generated them.

The heat budget of the basin has been shown to have a strong signal at interannual time scales.

The isopycnal potential vorticity analysis of model results has shown that Levantine intermediate water renewal is not fully achieved in the model experiments, probably because the climatological heat and momentum fluxes are too weak.

The transient tracer data (chlorofluorocarbons, tritium and helium-3) from general circulation surveys of the Eastern Mediterranean have been analysed with a box model and inverse methods. The experiments concentrate upon the analysis of the source of deep waters for the Eastern Mediterranean, the Adriatic Sea and its outflow from the sill of Otranto to arrive in the abyssal Ionian basin. New convection schemes were developed and applied. These new co nvection schemes improve the tracer distribution in vertical. The horizontal tracer distribution can be reproduced to a very large extent by the model advection schemes.

The deep and intermediate water formation process studies showed very interesting progress on the understanding and simulation of deep water convective plumes. After the plumes have mixed the water column to generate a dense chimney, the latter breaks up by baroclinic instability to form spinning cones which have a well defined and predictable scale.

The Princeton ocean model (POM) has been set up for the whole Aegean basin at different horizontal and vertical resolutions.
PROJECT DESCRIPTION:


The aims of this study can be summarised as follows:
1) The realistic simulation of the mesoscale
variability on seasonal time scales with a
primitive equation Eddy resolving General
Circulation Model (EGCM) of the whole
Mediterranean basin. The model will include up to
date air-sea exchange physical parameterizations
and turbulent closure schemes for vertical
mixing.
2) The simulation of the interannual and seasonal
Levantine Intermediate Water (LIW) and Deep Water
(DW) formation rates and their spatial
distribution.
3) The understanding of the vorticity dynamics in
the basin via quasi-geostrophic simulations of
the wind driven circulation and the definition of
the sources of the mesoscale field in the overall
basin.
4) The calculation of the renewal time of the
intermediate and deep water masses based upon a
transient tracer data set and the implementation
of these data into the EGCM.
5) The description of the Aegean basin circulation
variability from hydrological data analysis and
the development of a subregional model coupled
with the EGCM.
6) The description of the Adriatic sea thermohaline
circulation as given by the EGCM simulations and
by chemical and hydrological data sets analysis.

Coordinator

Consiglio Nazionale delle Ricerche (CNR)
Address
Via Emilia Est 770
41100 Modena
Italy

Participants (6)

ARISTOTLE UNIVERSITY OF THESSALONIKI
Greece
Address
University Campus, Egnatia Street, Administration
54006 Thessaloniki
IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE
United Kingdom
Address
South Kensington Campus
London
NATIONAL AND KAPODISTRIAN UNIVERSITY OF ATHENS
Greece
Address
Christou Lada Street 6
10561 Athens
NATIONAL RESEARCH COUNCIL OF ITALY
Italy
Address
Largo Fiera Della Pesca 1
60125 Ancona
NATIONAL RESEARCH COUNCIL OF ITALY
Italy
Address
Viale Romolo Gessi 2
34123 Trieste
UNIVERSITAET BREMEN
Germany
Address
Bibliothekstrasse 1
28334 Bremen