Asymmetric Modulation of ENSO Teleconnections by the Interdecadal Pacific Oscillation

AbstractRemote influences of ENSO are known to vary with different phases of the Interdecadal Pacific Oscillation (IPO). Here, observational and reanalysis data from 1920-2014 are analyzed to present a global synthesis of IPO’s modulation on ENSO teleconnections, followed by a modeling investigation. Regressions of surface air temperature (T), precipitation (P) and atmospheric circulations upon IPO and ENSO indices reveal substantial differences between ENSO and IPO teleconnections to regional T and P in the spatial pattern, magnitude and seasonality. The IPO’s modulation on ENSO teleconnections asymmetrically vary with both IPO and ENSO phases. For a given ENSO phase, IPO’s modulations are not symmetrically between its two phases; for a given IPO SST anomaly, its influence depends on whether it is superimposed on El Nino, La Nina, or neutral ENSO. The IPO modulations are linked to the response to tropical SST anomalies in the local Hadley circulation and the local Walker circulation at low latitudes, and...