460
LAURENCE CROSNIER
x The Mean Sea Surface Height (henceforth MSSH) (m) used as a
reference sea level during the assimilation procedure. Each system is
using a different MSSH field (cf section 2.4). Differences in the
MSSH fields between the systems can be large is some areas and are
shown to have major influence on the system behaviour (Birol et al.
2004).
The three dimensional fields are:
x The potential temperature (°C) and salinity (psu). Those Class 1
metrics allow to test the consistency and quality of the systems. For
example, the comparison of the monthly mean Class 1 fields to
available climatologies (Levitus 1998; Reynaud et al. 1998;
Medatlas 2002) can put in light drifts in the systems away from
initial climatological conditions at depths because of long spin-up.
Such tests have been used in recent inter-comparison experiments
such as DYNAMO (Meincke et al. 2001) and DAMÉE (Chassignet
and Malanotte-Rizzoli, 2000).
x The zonal and meridional velocity fields (m/s). A derived Class 1
diagnostic is the surface Eddy Kinetic Energy (EKE) which can be
computed using surface Class 1 velocities and compared to EKE
observations derived from satellite altimetry (Ducet and Le Traon,
2001).
3.3. Class 2 metrics
Class 2 diagnostics are interpolated on high 10km resolution vertical
sections (Figures 1 and 2). Class 2 fields are:
x The potential temperature (°C) and salinity (psu). The vertical
Class 2 sections can be compared, when possible, to historical
WOCE synoptic sections. This brings relevant insights on the
systems water masses characteristics, for example the 18°C Mode
Water (Worthington, 1959), Madeira Mode Water (Siedler et al.
1987), or the Mediterranean Water outflow (Bryden and Kinder,
1991). Class 2 model sections can also be compared to observed
XBT MEDS sections gathered within the SOOP program.
x The zonal and meridional velocity fields (m/s). Those Class 2
bring information on the vertical structure of currents, as for
example, the Deep Western Boundary Current below the Gulf
Stream transporting North Atlantic Deep Water (Willebrand et al.
2001; Lee et al. 1996), the Azores current (Paillet and Mercier,
1997; Sy, 1988) and the North Brazil Current (Johns et al. 1998;
Schott et al. 1998; Stramma and Schott, 1996). Class 2 model
velocities can also be compared to observed ADCP data.
LAURENCE CROSNIER
x The Mean Sea Surface Height (henceforth MSSH) (m) used as a
reference sea level during the assimilation procedure. Each system is
using a different MSSH field (cf section 2.4). Differences in the
MSSH fields between the systems can be large is some areas and are
shown to have major influence on the system behaviour (Birol et al.
2004).
The three dimensional fields are:
x The potential temperature (°C) and salinity (psu). Those Class 1
metrics allow to test the consistency and quality of the systems. For
example, the comparison of the monthly mean Class 1 fields to
available climatologies (Levitus 1998; Reynaud et al. 1998;
Medatlas 2002) can put in light drifts in the systems away from
initial climatological conditions at depths because of long spin-up.
Such tests have been used in recent inter-comparison experiments
such as DYNAMO (Meincke et al. 2001) and DAMÉE (Chassignet
and Malanotte-Rizzoli, 2000).
x The zonal and meridional velocity fields (m/s). A derived Class 1
diagnostic is the surface Eddy Kinetic Energy (EKE) which can be
computed using surface Class 1 velocities and compared to EKE
observations derived from satellite altimetry (Ducet and Le Traon,
2001).
3.3. Class 2 metrics
Class 2 diagnostics are interpolated on high 10km resolution vertical
sections (Figures 1 and 2). Class 2 fields are:
x The potential temperature (°C) and salinity (psu). The vertical
Class 2 sections can be compared, when possible, to historical
WOCE synoptic sections. This brings relevant insights on the
systems water masses characteristics, for example the 18°C Mode
Water (Worthington, 1959), Madeira Mode Water (Siedler et al.
1987), or the Mediterranean Water outflow (Bryden and Kinder,
1991). Class 2 model sections can also be compared to observed
XBT MEDS sections gathered within the SOOP program.
x The zonal and meridional velocity fields (m/s). Those Class 2
bring information on the vertical structure of currents, as for
example, the Deep Western Boundary Current below the Gulf
Stream transporting North Atlantic Deep Water (Willebrand et al.
2001; Lee et al. 1996), the Azores current (Paillet and Mercier,
1997; Sy, 1988) and the North Brazil Current (Johns et al. 1998;
Schott et al. 1998; Stramma and Schott, 1996). Class 2 model
velocities can also be compared to observed ADCP data.