I
v1
.....
Y2
sO
a
Numerical Models
371
. . . . 4
"
...... 4
. . . . v
.. v
. .
. . . .
I
Yb
4
4
4
. . YsL
.. ..
. .
y
Y't",.A A
1 1
A
1
Yb
b Ye
Fig. 6.7.2a,b. As in Fig. 6.7.1 except that the parameters of the calculation yield a shadow zone
boundary which strikes the equator within the basin. In this case the EUC is fed from the
subtropical gyre through the interior as well as the western boundary current. (From McCreary and
Lu 1994)
momentum equations while the vertical equation of motion is the hydrostatic
balance). It contains 27levels in the vertical and its horizontal resolution is 1°
in longitude by 1/3° in latitude. It has a fairly substantial horizontal mixing
coefficient (AH = 2 x 10 7 cm 2 /s), and its vertical mixing coefficient depends on
the Richardson number, Ri = [N 2 /l8uj8zl 2 ] in such a way that in regions of
low static stability or high shear the mixing rate is increased. The model includes the subtropical gyre in both hemispheres.
Philander and Pacanowski used their model to simulate both the mean and
time-dependent circulations of the equatorial zone, and the model results agree
favorably with observations, although the model undercurrent is both weaker
than observed in the simulation for the Atlantic and also suffers a too rapid
loss of fluid by entrainment into the mixed layer. The equatorial thermocline as
computed in the model gradually decays due to anomalous warming, and this
is related to deficiencies in the model's representation of the link with the cold
deep water of the subtropical gyre. Nevertheless it is to date the most distinguished and successful numerical simulation of realistic equatorial conditions.
The relative completeness of the model naturally also produces the spectre
of complexity, and only recently have analyses of the model's results focused
on the processes of the kind discussed in this chapter. Rather surprisingly, not
until the very interesting and revealing analysis of Wacongne (1989) was it
possible to describe and diagnose the equatorial dynamical balances of the
model.
SON
y~
y
Eq
v1
.....
Y2
sO
a
Numerical Models
371
. . . . 4
"
...... 4
. . . . v
.. v
. .
. . . .
I
Yb
4
4
4
. . YsL
.. ..
. .
y
Y't",.A A
1 1
A
1
Yb
b Ye
Fig. 6.7.2a,b. As in Fig. 6.7.1 except that the parameters of the calculation yield a shadow zone
boundary which strikes the equator within the basin. In this case the EUC is fed from the
subtropical gyre through the interior as well as the western boundary current. (From McCreary and
Lu 1994)
momentum equations while the vertical equation of motion is the hydrostatic
balance). It contains 27levels in the vertical and its horizontal resolution is 1°
in longitude by 1/3° in latitude. It has a fairly substantial horizontal mixing
coefficient (AH = 2 x 10 7 cm 2 /s), and its vertical mixing coefficient depends on
the Richardson number, Ri = [N 2 /l8uj8zl 2 ] in such a way that in regions of
low static stability or high shear the mixing rate is increased. The model includes the subtropical gyre in both hemispheres.
Philander and Pacanowski used their model to simulate both the mean and
time-dependent circulations of the equatorial zone, and the model results agree
favorably with observations, although the model undercurrent is both weaker
than observed in the simulation for the Atlantic and also suffers a too rapid
loss of fluid by entrainment into the mixed layer. The equatorial thermocline as
computed in the model gradually decays due to anomalous warming, and this
is related to deficiencies in the model's representation of the link with the cold
deep water of the subtropical gyre. Nevertheless it is to date the most distinguished and successful numerical simulation of realistic equatorial conditions.
The relative completeness of the model naturally also produces the spectre
of complexity, and only recently have analyses of the model's results focused
on the processes of the kind discussed in this chapter. Rather surprisingly, not
until the very interesting and revealing analysis of Wacongne (1989) was it
possible to describe and diagnose the equatorial dynamical balances of the
model.
SON
y~
y
Eq