Primitive Equation Modelling ofPlankton Ecosystems
425
chlorophyll concentration. This source error was reduced by increasing the number
of particles to 200 per layer. Then it no longer contributed significantly to the SeaWIFS ETT error.
The optical boundary condition (e S )
The error in the optic al boundary condition e S was reduced significantly by introducing more modern treatments of radiation in the clear air (Gregg and Carder
(1990; Anderson 1993). Using this improved method to calculate the optical
boundary condition led to a substantial change in the Azores VPE. The mismatch
between simulation and observation of the timing of the peak in the spring bloom
was halved.
Summary
Liu et al (2001) concluded that, as expected, the errors in the optics ofthe original Azores VPE did make a significant contribution to the mismatch between simulation and observation of the spring bloom. Comparison with independent data
showed that there were significant source errors in the model, the boundary conditions and the particle management rules. When these were corrected, by using
improved codes and more particles, the new version of the Azores VPE featured a
spring bloom that better matched the observations from SeaWIFS. The difference
was halved by improving the optics in the simulation. That was encouraging. It was
perhaps surprising that reduc ing e d by an order of magnitude made no contribution
to that improvement. However, it makes sense that the larger impact is with the surface boundary condition, which determines the total flux of solar energy entering
the water, rather than with the optical code, which merely controls the penetration
ofthat flux. The lesson is that ranking the magnitude of source errors may not indicate which are most important in determining the accuracy of features in the virtual
plankton ecosystem.
18.19 The Virtual Ecology Workbench (VEW)
The Virtual Ecology Workbench provides user-friendly access to LE modelling.
It requires no skill in computer programming. The VEW has four levels of operation:
1) VEWdata (Fig. 18.11) supports analysis ofprescribed Virtual Plankton Ecosystems
2) VEW controller allows the user to change the values of parameters in a
prescribed model. Aiso to create the initial and boundary conditions used to
integrate it; these conditions are generated automatically by VEWTrackgen.
3) VEWmodeller allows the user to create new LE models from prescribed science
and technology modules.
425
chlorophyll concentration. This source error was reduced by increasing the number
of particles to 200 per layer. Then it no longer contributed significantly to the SeaWIFS ETT error.
The optical boundary condition (e S )
The error in the optic al boundary condition e S was reduced significantly by introducing more modern treatments of radiation in the clear air (Gregg and Carder
(1990; Anderson 1993). Using this improved method to calculate the optical
boundary condition led to a substantial change in the Azores VPE. The mismatch
between simulation and observation of the timing of the peak in the spring bloom
was halved.
Summary
Liu et al (2001) concluded that, as expected, the errors in the optics ofthe original Azores VPE did make a significant contribution to the mismatch between simulation and observation of the spring bloom. Comparison with independent data
showed that there were significant source errors in the model, the boundary conditions and the particle management rules. When these were corrected, by using
improved codes and more particles, the new version of the Azores VPE featured a
spring bloom that better matched the observations from SeaWIFS. The difference
was halved by improving the optics in the simulation. That was encouraging. It was
perhaps surprising that reduc ing e d by an order of magnitude made no contribution
to that improvement. However, it makes sense that the larger impact is with the surface boundary condition, which determines the total flux of solar energy entering
the water, rather than with the optical code, which merely controls the penetration
ofthat flux. The lesson is that ranking the magnitude of source errors may not indicate which are most important in determining the accuracy of features in the virtual
plankton ecosystem.
18.19 The Virtual Ecology Workbench (VEW)
The Virtual Ecology Workbench provides user-friendly access to LE modelling.
It requires no skill in computer programming. The VEW has four levels of operation:
1) VEWdata (Fig. 18.11) supports analysis ofprescribed Virtual Plankton Ecosystems
2) VEW controller allows the user to change the values of parameters in a
prescribed model. Aiso to create the initial and boundary conditions used to
integrate it; these conditions are generated automatically by VEWTrackgen.
3) VEWmodeller allows the user to create new LE models from prescribed science
and technology modules.