Figure 3.3: Time series of Southern Oscillation Index (upper panel) and Interdecadal Pacific Oscillation (lower panel) from 1920 to 2000
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Text description of figure
The upper panel in this figure displays a time series of the Southern Oscillation Index for the period from 1920 to 2000. Persistence of this index below about minus one coincides with El Niño events, and periods above positive one with La Niña events. The Southern Oscillation Index varies between about three and seven years and large variability exists in the intensity of individual events.
The lower panel shows a time series of the Interdecadal Pacific Oscillation from the period from 1920 to 2000. Three phases are identified in the figure: positive phases from 1922 to 1944 and again from 1978 to 1998, and a negative phase from 1946 to 1977.
