BLUELINK
433
products. Surface currents will be estimated from images of remotely-sensed
sea-surface temperatures, using a method that tracks the movements of
small-scale features. A high-quality enhanced regional wind speed and
direction product will also be developed.
3.2
Modelling and assimilation system
3.2.1
Global model and data assimilation system
BLUElink has developed a global ocean model based on the GFDL
MOM4 code (Griffies et al., 2004), called the Ocean Forecasting Australia
Model (OFAM), with a resolution telescoping from 2º in the North Atlantic
and North Pacific to (1/10)º in the Asian-Australian region. The AsianAustralian region is defined as extending from longitudes 90º E to 180º E,
and from latitude 16º N to 75º S which is very similar in extent to the part of
the earth shown in Fig. 1. OFAM has 47 vertical levels with 35 levels in the
top 1000 m and a thickness of the uppermost levels of 10 m. The model uses
the third-order “quicker” scheme for tracer advection (Leonard, 1979), a
hybrid mixed-layer model based on Chen et al. (1994), viscosity mixing
based on Smagorinsky (1993) and isopycnal mixing with the GentMcWilliams parameterisation of eddy-induced stirring (Gent and
McWilliams, 1990). Due to the model’s variable grid size anisotropic
options have been chosen for the latter two parameterisations.
OFAM will form the backbone of the operational ocean forecasting
system run by the Bureau of Meteorology. A multivariate Optimum
Interpolation scheme (BODAS) is used to assimilate ocean observations in
near-real time into the model to improve the initial conditions of the
forecasts. A schematic diagram of this forecast system is presented in Fig. 5.
BODAS is a stand-alone system that is intended to be adaptable to other
ocean models. BODAS calculates a global analyses of surface height K,
temperature T, salinity S and the horizontal components of current (u, v) by
combining a forecast from OFAM with observations of sea-level anomaly
(SLA) from along-track altimetry and temperature and salinity from various
sources including Argo profiles, CTD surveys and moored arrays. BODAS
performs this calculation through a series of steps that are summarized as
follows:
1. Calculate analysis of K, T and S
2. Convectively adjust T and S
3. Spatially filter increments of K, T and S
4. Calculate geostrophic increments for u and v
(or use statistical approach).
433
products. Surface currents will be estimated from images of remotely-sensed
sea-surface temperatures, using a method that tracks the movements of
small-scale features. A high-quality enhanced regional wind speed and
direction product will also be developed.
3.2
Modelling and assimilation system
3.2.1
Global model and data assimilation system
BLUElink has developed a global ocean model based on the GFDL
MOM4 code (Griffies et al., 2004), called the Ocean Forecasting Australia
Model (OFAM), with a resolution telescoping from 2º in the North Atlantic
and North Pacific to (1/10)º in the Asian-Australian region. The AsianAustralian region is defined as extending from longitudes 90º E to 180º E,
and from latitude 16º N to 75º S which is very similar in extent to the part of
the earth shown in Fig. 1. OFAM has 47 vertical levels with 35 levels in the
top 1000 m and a thickness of the uppermost levels of 10 m. The model uses
the third-order “quicker” scheme for tracer advection (Leonard, 1979), a
hybrid mixed-layer model based on Chen et al. (1994), viscosity mixing
based on Smagorinsky (1993) and isopycnal mixing with the GentMcWilliams parameterisation of eddy-induced stirring (Gent and
McWilliams, 1990). Due to the model’s variable grid size anisotropic
options have been chosen for the latter two parameterisations.
OFAM will form the backbone of the operational ocean forecasting
system run by the Bureau of Meteorology. A multivariate Optimum
Interpolation scheme (BODAS) is used to assimilate ocean observations in
near-real time into the model to improve the initial conditions of the
forecasts. A schematic diagram of this forecast system is presented in Fig. 5.
BODAS is a stand-alone system that is intended to be adaptable to other
ocean models. BODAS calculates a global analyses of surface height K,
temperature T, salinity S and the horizontal components of current (u, v) by
combining a forecast from OFAM with observations of sea-level anomaly
(SLA) from along-track altimetry and temperature and salinity from various
sources including Argo profiles, CTD surveys and moored arrays. BODAS
performs this calculation through a series of steps that are summarized as
follows:
1. Calculate analysis of K, T and S
2. Convectively adjust T and S
3. Spatially filter increments of K, T and S
4. Calculate geostrophic increments for u and v
(or use statistical approach).