The Interdecadal Pacific Oscillation, or IPO, is a large-scale, long period oscillation that influences climate variability over the Pacific Basin. The IPO operates at a multi-decadal scale, with phases lasting around 20 to 30 years.
During the positive phase of the IPO, precipitation is generally higher than normal northeast of the South Pacific Convergence Zone and lower than normal southwest of the SPCZ. Mean sea level pressures are higher than normal to the west of the dateline and lower than normal to the east of the dateline. Due to these pressure differences, there is a southerly flow anomaly during the positive phase of the IPO.
Under the Climate Present and Past project, NIWA undertakes research about the Interdecadal Pacific Oscillation in the following areas: