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MICHAEL J. BELL ET AL.
challenges inherent in developing these systems. It describes some
representative examples of scientific trouble-shooting and some
investigations of the impact of new observations and changes to assimilation
methods on the performance of the system. The final section attempts to give
an historical perspective. It summarises first the 20-year history of the
FOAM project and then the changing world context in which it has been
developing. Finally four major changes in the direction of the FOAM project
are described and related to this changing context.
2.
Description of the FOAM system
2.1
Overview and present configurations
The FOAM system produces 5-day forecasts of three-dimensional ocean
temperatures, salinities and currents and sea-ice properties on a routine daily
basis. It assimilates temperature profile data, surface height data from
satellite-borne altimeters and satellite and in situ surface temperature data
and is driven by 6-hourly surface fluxes from the Met Office’s Numerical
Weather Prediction (NWP) system. High resolution model configurations
are nested inside the global configuration. Statistics on the differences
between the model forecasts and observations are routinely produced and
reanalyses can be generated from 1997 onwards.
The FOAM configurations that are presently run on a routine daily basis
within the operational suite at the Met Office cover the globe with a 1
o grid;
the Atlantic and Arctic Oceans and the Indian Ocean with 35 km grids; and
the North Atlantic, the Mediterranean Sea and the Arabian Sea with 12 km
grids. An Antarctic configuration with a 27 km grid is also run on a daily
basis and is to be transferred into the operational suite in the first half of
2005. All of these configurations have 20 vertical levels. The global,
Atlantic and Arctic, and N Atlantic configurations are illustrated in figure 1.
2.2
Inputs
Six-hourly full-resolution surface-flux fields from the global forecasts
by the Met Office’s NWP system to 5-days ahead are currently used to drive
all the FOAM configurations (in future fluxes from limited-area forecasts
will drive some configurations). The flux fields used are the wind stress
(vector with two components), wind mixing energy, penetrating heat flux,
non-penetrating heat flux and precipitation minus evaporation. The NWP
system calculates fluxes over sea-ice and open water ( leads ) separately and
combines them using sea-ice concentration analyses generated by NCEP.
The surface temperature and salinity fields are also weakly relaxed towards
the monthly Levitus et al (1998) climatologies.
.
“
”
MICHAEL J. BELL ET AL.
challenges inherent in developing these systems. It describes some
representative examples of scientific trouble-shooting and some
investigations of the impact of new observations and changes to assimilation
methods on the performance of the system. The final section attempts to give
an historical perspective. It summarises first the 20-year history of the
FOAM project and then the changing world context in which it has been
developing. Finally four major changes in the direction of the FOAM project
are described and related to this changing context.
2.
Description of the FOAM system
2.1
Overview and present configurations
The FOAM system produces 5-day forecasts of three-dimensional ocean
temperatures, salinities and currents and sea-ice properties on a routine daily
basis. It assimilates temperature profile data, surface height data from
satellite-borne altimeters and satellite and in situ surface temperature data
and is driven by 6-hourly surface fluxes from the Met Office’s Numerical
Weather Prediction (NWP) system. High resolution model configurations
are nested inside the global configuration. Statistics on the differences
between the model forecasts and observations are routinely produced and
reanalyses can be generated from 1997 onwards.
The FOAM configurations that are presently run on a routine daily basis
within the operational suite at the Met Office cover the globe with a 1
o grid;
the Atlantic and Arctic Oceans and the Indian Ocean with 35 km grids; and
the North Atlantic, the Mediterranean Sea and the Arabian Sea with 12 km
grids. An Antarctic configuration with a 27 km grid is also run on a daily
basis and is to be transferred into the operational suite in the first half of
2005. All of these configurations have 20 vertical levels. The global,
Atlantic and Arctic, and N Atlantic configurations are illustrated in figure 1.
2.2
Inputs
Six-hourly full-resolution surface-flux fields from the global forecasts
by the Met Office’s NWP system to 5-days ahead are currently used to drive
all the FOAM configurations (in future fluxes from limited-area forecasts
will drive some configurations). The flux fields used are the wind stress
(vector with two components), wind mixing energy, penetrating heat flux,
non-penetrating heat flux and precipitation minus evaporation. The NWP
system calculates fluxes over sea-ice and open water ( leads ) separately and
combines them using sea-ice concentration analyses generated by NCEP.
The surface temperature and salinity fields are also weakly relaxed towards
the monthly Levitus et al (1998) climatologies.
.
“
”