There are several reasons why a
barotropic model is interesting and important per se. The first,
and most important, has been discussed above, i.e. that the free
surface elevation couples directly to the barotropic mode.
Satellite altimeter measurements
of the free surface elevation are
one of the important data fields used as part of the
initialization and updating procedures for real-time ocean
prediction. Thus information from altimeters may first enter the
ocean model through the barotropic mode, where it represents a
direct forcing (see a similar data forcing with tide gauge
information in section 6.)
A second feature of
barotropic models is the presence of the fast free surface gravity
waves.
The simple explicit finite-difference schemes treating such
waves are subject to severe time step limitations, so that
solution of the barotropic mode may lead to large CPU
requirements. Thus it is important to study the solution of this
system with efficient numerical schemes, before incorporating it
into the general 3-D baroclinic--barotropic ocean model. For a
discussion of explicit and implicit methods, as well as
limitations on the time step, the student should consult
section 2.4.
Figure 5: Breakdown of Barotropic Models.
