471
Pbase I
PhaseS
Pbase 2
Phase 6
Pbase3
Phase 7
Pbase4
PhaseS
Figure 12: Composites of 700 mb geopotential height anomalies (in meters) over the
Pacific sector; the 8 composites correspond to equidistant phases covering one half of the
life cycle of the 40- 45 day oscillation isolated as an M-SSA pair (courtesy of R. Vautard).
oscillatory pair in observations or proxy records has gone hand in hand
with the description of a Hopf bifurcation in a (hierarchy of) model(s);