Seasonal Atlas of
the Western Mediterranean Sea
from climatologies and
high resolution numerical models of Mercator
by FLORE MOUNIER1,2,
Karine Béranger1,2, Romain Bourdalle-Badie3, Yann Drillet3 & Laure Siefridt3
1LODYC,
Tour 26, 4e étage, boite 100, 4 Place Jussieu, 75252 Paris Cedex 05, France
mounier@lodyc.jussieu.fr, beranger@lodyc.jussieu.fr
2ENSTA,
UME, Chemin de la Hunière, 91761 Palaiseau Cedex, France
3CERFACS,
Mercator Project, Gustave Coriolis, Toulouse, France
bourdall@cerfacs.fr, drillet@cerfacs.fr,,siefridt@cerfacs.fr
Introduction
Results from modelling projects and climatological databases for the Mediterranean
Sea are now available. This atlas has been designed as a flexible tool to compare
outputs from general circulation models with climatologies derived from observations.
It has been implemented for PAM and MED16 present simulations (see part I) but it
will be used for further simulations.
Basically, in the Western Mediterranean Sea, three major water masses are identified
according to their formation sites:



- one in the upper layer, the Modified Atlantic Water (MAW) which originates
from the Strait of Gibraltar;
- another one at mid-depth, the thick layer of the Levantine Intermediate Water
(LIW), that propagates from the eastern basin to the western basin;
- and finally one at the bottom, which is a reservoir filled by Western
Mediterranean Deep Water (WMDW) which are produced during the winter
season in the Gulf of Lions.
This atlas allows to compare views of seasonal horizontal distributions of properties
at significant levels of these water masses : temperature, salinity, velocities, eddy
Kinetic Energy. The barotropic stream function is also available. Seasonal vertical
distributions of temperature and salinity are shown for 11 preselected sections.
Part I provides a description of the four simulations and Part II shortly describes the
two climatologies. Part III describes useful information concerning the positions of the
vertical sections and the descriptions of the figures.
I. Simulations from high resolution models of Mercator
A very high resolution model of the Mediterranean Sea has been developed in the
context of the MERCATOR project (Bahurel et al., 2002; www.mercator.com.fr). The
PAM model (the Atlantic-Mediterranean Prototype, in French 'Prototype Atlantique
Méditerranée'; Drillet et al., 2000; Béranger et al., 2001; Siefridt et al., 2002) uses a
1/16°coshorizontal grid mesh (the latitude), and 43 z-levels on the vertical. The
horizontal grid is stretched at Gibraltar in order to better fit the coast line (Blanchet
and Siefridt, 1998). The topography is based on the 1/30° bathymetry (Smith and
Sandwell, 1997) averaged onto the 1/16° grid. The numerical model is an extended
version of the primitive equation numerical model OPA (Ocean PArallel, Madec et al.,
1997) with the rigid lid approximation. The horizontal diffusion is parameterised by a
biharmonic operator. On the vertical, the mixing is parameterised by a turbulent
kinetic energy scheme. The model has been forced by daily atmospheric fluxes from
ECMWF analyses over the period March 1998 to June 2002. This choice was
motivated by the relatively fine resolution of the fluxes allowed from March 1998 at
the ECMWF centre (0.5° per 0.5°, TL319 grid). It is know that the resolution of the
atmospheric forcings can play a major role to simulate some circulation patterns
(Horton et al., 1994; Lascaratos and Hatziapostolou, 2001). The fluxes are applied
using the flux correction method (Barnier et al., 1995) with a retroaction coefficient .
In the retroaction term, the model sea surface temperature (SST) is relaxed to the
climatological SST. Freshwater fluxes (Evaporation, Precipitation, River runoffs) are
put as a virtual salt flux, with an added term that relaxes the model sea surface
salinity (SSS) toward the climatological SSS. For the Mediterranean Sea, runoffs of
31 rivers (Vörösmarty et al., UNESCO, 1996) are incorporated using an upstream
scheme at the river mouth. The Black Sea discharge is modelled using the estimates
of Stanev et al. (2000). The Atlantic Ocean initial state was provided by the seasonal
climatology of Reynaud et al. (1998) . The simulations PAM-20 and PAM-21 (see
below), which have been incorporated in this atlas have been computed at the
ECMWF centre (Drillet et al., 2000).
The second model MED16 uses the Mediterranean the configuration of the PAM
model but on a smaller domain. MED16 has been extracted from the PAM model and
the exchanges with the Atlantic Ocean are modelled by an Atlantic box (bufferzone).
The simulations MED16-05 and MED16-07 (see below) have been done at the IDRIS
centre (Béranger, 2001; Béranger et al., 2002).
1. PAM simulations
In the PAM model, the diffusivity coefficients are taken equal to -3.109 m2.s-1 for the
tracers and equal to –9.109 m2.s-1 for the velocities. A free slip condition is used and
the time step is 900s. Only the major Mediterranean rivers (large runoff) are
represented according to MED16.
PAM-20
- Duration of the simulation : about 5 years
- Initial state in the Mediterranean Sea : MODB5 seasonal climatology
- Atmospheric forcing : the PAM model has been forced, during 16 months by the
daily fluxes averaged over the period March 1998 to February 2001, and then by
interannual fluxes from March 1998 to February 2001
- Retroaction term for SST : the model SST is relaxed to the weekly SST of Reynolds
estimated from satellite data, with a constant coefficient equal to –20 W.m-2
- Relaxation term for SSS : the model SSS is relaxed to the MODB5 climatological
SSS with a constant coefficient equivalent to =–20 W.m-2 .
PAM-21
- Duration of the simulation : about 5 years
- Initial state in the Mediterranean Sea : MEDATLAS-II seasonal climatology (that
comes from an averaged of monthly means)
- Atmospheric forcing : the PAM model has been forced, during 16 months by the
daily fluxes averaged over the period March 1998 to February 2001, and then by
interannual fluxes from March 1998 to June 2002
- Retroaction term for SST : constant coefficient equal to -40 W.m-2, using
Reynolds SST
-Relaxation term for SSS : constant coefficient equivalent to -40 W.m-2, using
MEDATLAS-II climatological SSS.
MED16 simulations
1.
In the MED16 model, the diffusivity coefficients are taken equal to -4.109 m2.s-1 for
tracers and velocities. A no slip condition is used at the coast. The time step is 600s.
MED16-05
- Duration of the simulation : 11 years
- Initial state : MODB5 seasonal climatology
- Atmospheric forcing : daily air-sea surface fluxes applied in a yearly perpetual mode
(period March 1998 to February 1999)
- Retroaction term for SST : constant coefficient equal to -40 W.m-2 using
Reynolds SST
- Relaxation term for SSS : constant coefficient equivalent to -40 W.m-2 using
MODB5 climatological SSS.
MED16-07
- Duration of the simulation : 13 years
- Initial state in the Mediterranean Sea: MEDATLAS-II monthly climatology
- From year 1 to year 8 :
- Amospheric forcing : daily fluxes applied in a yearly perpetual mode (year
2000). The net heat flux has been corrected by a factor of 1.12 to allow the
heat budget to be equal to –7 W.m-2 over the Mediterranean Sea, a value
commonly known (Béthoux, 1980)
- Retroaction term for SST : the model SST is relaxed to the climatological
SST with a coefficient . ranges from –10 in winter to –40 W.m-2 in
summer. Spatial means of this retroaction term have been applied over a
box of half a degree
- Relaxation term for SSS : the model SSS is relaxed to the MEDATLAS-II
climatological SSS with a coefficient equivalent to =–40 W.m-2. Spatial
means of this relaxation term have been applied over a box of half a
degree
- From year 9 to year 13 :
- Atmospheric forcing: daily fluxes over the period March 1998 to June
2002. No correction of the net heat flux budget was applied (balance
around -30 W.m-2). The net evaporation budget is about 700 mm.yr-1, a
value in agreement with the compilation of Boukthir and Barnier (2000)
- Retroaction term for SST : the model SST is relaxed to the weekly SST of
Reynolds (2 and spatial means) from March 1998 to December 2000, and
then to the daily SST of Reynolds (2 and spatial means) from January
2001 to May 2002
- Relaxation term for SSS : the model SSS is relaxed to the MEDATLAS-II
climatological SSS with a coefficient equivalent to = –40 W.m-2 (spatial
means).
II. Climatologies
Two climatologies have been used for the initial state of the models. The MODB5
seasonal climatology of Brasseur et al. (1996) and the monthly climatology of the
MEDATLAS/MEDAR group (2002). These climatologies have been interpolated onto
the Mediterranean grid of the PAM-MED16 models. These interpolated fields are
showed in this atlas. More informatiosn are available at the following WWW
locations :
MEDATLAS:
and
http://modb.oce.ulg.ac.be/Medar/medar.html
http://www.ifremer.fr/sismer/program/medar/
MODB
http://modb.oce.ulg.ac.be/atlas/atlas.html
III. Useful informations
1. Atlas interface
Access to the data can be done by two different ways:
- Through the html interface by selecting a figure with a click on the mouse, a quick
look of a low resolution which size is adjusted user’s screen size
- By downloading the figure (jpeg format), a high resolution figure can be obtained.
The atlas is organised in two parts given on the main page of the interface : model
results and climatologies. For both, figures for the four seasons are proposed (winter
= January to March). A selection of sections (Part III.1) is proposed for each
parameter.
2. Sections available in the atlas
- Horizontal sections are located at surface and 400 meter depth levels.
- A full line and a name on the following figure indicate vertical sections. Their
detailed positions are given in Tab.1. The vertical fields are characterised by a colour
scale that does not change neither with seasons nor with sections. On the other
hand, the contour scales change according to season and section to follow easily the
major water masses through the whole basin.
Begin
End
Section
Longitude
Latitude
Longitude
Latitude
MED1
-5.65°E
35.78°N
-5.90°E
36.15°N
MED3-4
3.09°E
36.08°N
3.09°E
41.78°N
MED5
1.55°E
39.10°N
2.41°E
39.55°N
MED8
9.16°E
37.10°N
9.16°E
39.16°N
MED9
9.47°E
42.98°N
9.47°E
44.42°N
MED10
9.59°E
42.43°N
11.16°E
42.43°N
MED11
11.09°E
37.05°N
12.53°E
37.99°N
MED26
0.28°E
36.04°N
0.28°E
38.73°N
MED27
4.34°E
39.84°N
16°E
39.84°N
MED28
0.16°E
38.63°N
1.28°E
38.92°N
MED29
6.28°E
36.85°N
6.28°E
42.98°N
Tab.1: Geographical coordinates of the vertical sections presented in the atlas.
3.
4.
3. Figures
Model results: temperature, salinity, velocity, barotropic stream function,
and eddy kinetic energy
For each parameter, the same section (Tab.1) is plotted for the four simulations, and
is indicated at the top of the figure, with the chosen season, the location of the model
results inside the figure, and, the name of the chosen parameter. The same palette is
used for the four figures.
For example, for the potential temperature in winter at the vertical section med1, the title of the figure
is :
' Section : med1 / Season: Winter / MED16-05 (top-left), MED16-07 (top-right), PAM-20 (bottom-left),
PAM-21 (bottom-right) / Temperature '
The winter temperature of MED16-05 is put at the top-left in the figure, the winter temperature of
MED16-07 is put at the top-right in the figure, the winter temperature of PAM-20 is put at the bottomleft in the figure, and the winter temperature of PAM-21 is put at the bottom-right in the figure.


Climatological fields: temperature and salinity
Temperature and salinity of the two climatologies have been plotted on the same
page. Figures are organised as follows : At the top of the page, the name of the
section is indicated with the chosen season, the location of the climatological results
inside the figure, and, the names of the chosen parameters. One common palette is
used per parameter.
For example, in winter at the vertical section med1, the title is :
Section : med1 / Season: Winter / MEDATLAS-II (left), MODB5 (right), Temperature (top), salinity
(bottom)
The winter temperature of MEDATLAS-II is put at the top-left in the figure, the winter temperature of
MODB5 is put at the top-right in the figure, the winter salinity of MEDATLAS-II is put at the bottom-left
in the figure, and the winter salinity of MODB5 is put at the bottom-right in the figure.

Useful information
Horizontal sections
TEMPERATURE
Isotherms every 0.05°C
VELOCITY
One vector of five is plotted (m.s-1)
SALINITY
Isohalines every 0.1 psu
EDDY KINETIC ENERGY
Isoclines every 0.5 cm2.s-2
BAROTROPIC STREAM FUNCTION
Isoclines every 1.5 Sv
Vertical sections
Annual
EDDY KINETIC ENERGY
Section
Isoclines in cm2.s-2
MED1
MED3-4
MED5
MED8
MED9
MED10
MED11
MED26
MED27
MED28
MED29
every 0.5 up to 5
then every 5
every 1 up to 10
then every 2.5
every 1 up to 10
then every 2.5
every 2
every 0.5
every 0.5
every 1
every 0.5 up to 5
then every 2
every 2
every 1
every 1 up to 10
then every 5
Winter & Autumn
TEMPERATURE
SALINITY
Isotherms in ° C
Isohalines in psu
Section
MED1
from 12.7 to 13.6 by 0.05
then every 0.4
from 12.4 to 13 by 0.05
MED3-4 then every 0.1 until 13.3
then every 0.5
from 36.3 to 37.5 by 0.2
then every 0.05 until 38.2
then every 0.025
from 36.3 to 38.2 by 0.1
then every 0.025
MED5
from 13 to 13.3 by 0.025
then every 0.1 until 13.5
then every 0.2
from 36.3 to 37.5 by 0.2
then every 0.05 until 38.2
then every 0.025
MED8
from 12.4 to 14 by 0.1
then every 0.4
from 37 to 38.6 by 0.1
then every 0.05
12.7
MED9 from 12.8 to 14.3 by 0.05
then every 0.4
from 37 to 37.9 by 0.2
then every 0.05
12.7
MED10 from 12.8 to 14.3 by 0.05
then every 0.4
from 37.3 to 37.9 by
0.05
then every 0.1
12.7
13.2
MED11
from 13.7 to 15 by 0.05
then every 0.25
from 37.3 to 38.6 by 0.1
then every 0.025
from 12.7 to 13.3 by 0.05
MED26 then every 0.1 until 14
then every 0.4
from 36.3 to 37.5 by 0.2
then every 0.05 until 38.2
then every 0.025
from 12.7 to 13.6 by 0.05
MED27
then every 0.2
from 37 to 38.4 by 0.2
then every 0.05 until 38.6
then every 0.025
MED28
from 12.7 to 13.6 by 0.05
then every 0.4
from 37 to 37.5 by 0.1
from 38.2 to 38.7 by 0.025
MED29
from 12.7 to 13.6 by 0.05
then every 0.4
from 37 to 38.4 by 0.1
then every 0.02
Spring & Summer
TEMPERATURE
SALINITY
Isotherms in °C
Isohalines in psu
section
MED1
from 12.8 to 13.9 by 0.1
then every 0.2 until 15
then every 0.4
from 12.4 to 13 by 0.05
MED3-4 then every 0.1 until 13.3
then every 0.5
from 35.5 to 38 by 0.5
then every 0.1
from 36.2 to 38.3 by 0.2
then every 0.025 until 38.7
then every 0.1
MED5
from 12.9 to 13.3 by 0.05
then every 0.5
from 37 to 38.1 by 0.5
then every 0.025 from 38.2
MED8
from 12.4 to 14 by 0.1
then every 0.4
from 37 to 38.4 by 0.2
then every 0.05 until 38.5
then every 0.025
MED9
12.7
from 12.8 to 14 by 0.1
then every 0.4
every 0.04 from 37.3
MED10
from 13 to 13.6 by 0.1
then every 0.1
from 37.3 to 38.5 by 0.1
then every 0.025
MED11
from 13.7 to 15 by 0.05
then every 0.1
from 37.3 to 37.9 by 0.1
then every 0.2
MED26 every 0.05 from 12.7
38.2 to 38.4 by 0.1
then 38.425
then every 0.01
MED27 every 0.1 from 12.7
38.4
38.45
38.525
then every 0.05
MED28
from 12.7 to 13.2 by 0.05
then every 0.4
from 37 to 38.225 by 0.2
then every 0.05
MED29
from 12.7 to 13.6 by 0.1
then every 0.4
from 37 to 38.422 by 0.2
then every 0.02
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