4.0
3.0
2.0
1::
. .
a.
0;
!!! 1.0
-
.ll! .,
= 0.0
-1.0
-2.0
431
-4.0
-3.0
-2.0
-1.0
0.0
-4.0
-3.0
-2.0
-1.0
0.0
'1 0"
theta(0.2)
1.0
1.0
2.0
3.0
4.0
3.0
2.0
1.0
0.0
-1.0
-2.0
2.0
3.0
Figure 8: Phase plane picture of the time-dependent behavior in a parameter region where
none of the three steady states is stable. The topography amplitude is bo = 538 m, the
two layers have equal mean heights 2500 m, the reduced gravity is 9'/9 = 0.001 and the
amplitude of the winds tress is TO = 1O-4m 2 S - 1.
leads to periodic oscillations of the zonal velocities. The amplitude of this
oscillation then reaches a level where the excitation of the Rossby wave is
stopped because the zonal velocity in the lower layer becomes to small. The
time span of this Rossby wave phase of the attractor is thus few propagation
times, of order "(f . The orbits then get attracted toward another unstable
steady state located in the upper right corner of the phase plane picture.
But this steady state is only halfway circled, the orbits finally get attracted