Bi-decadal and penta-decadal oscillations over the North Pacific
Shoshiro Minobe
Hokkaido University
The roles of interdecadal oscillations in climatic regime shifts, which are observed as rapid strength changes in the Aleutian low in winter to spring seasons, have been analyzed. A regime shift is attributed to simultaneous phase reversals between pentadecadal and bidecadal variations, which synchronize to each other with a relative period of three. The pentadecadal variation, which is observed both in winter and spring seasons, provided the basic timescale of regime shifts, while bidecadal variation, which is observed only in winter, characterizes the rapidity of the shifts. A Monte-Calro simulation shows that the simultaneous phase reversals between the pentadecadal and bidecadal variations reflect a physical linkage between them, and does not occur accidentally. Meanings of the synchronizing feature for the prediction of the regime shifts is discussed.
