Impact of different El Niño types on the El Niño/IOD relationship

Previous studies reported that positive phases of the Indian Ocean Dipole (IOD) tend to accompany El Niño during boreal autumn. Here we show that the El Niño/IOD relationship can be better understood when considering two different El Niño flavors. Eastern Pacific El Niño events exhibit a strong correlation with the IOD dependent on their magnitude. In contrast, the relationship between Central Pacific (CP) El Niño events and the IOD depends mainly on the zonal location of the sea surface temperature anomalies rather than their magnitude. CP El Niño events lying farther west than normal are not accompanied by significant anomalous easterlies over the eastern Indian Ocean along the Java/Sumatra coast, which is unfavorable for the local Bjerknes feedback and correspondingly for an IOD development. The El Niño/IOD relationship has experienced substantial changes due to the recent decadal El Niño regime shift, which has important implications for seasonal prediction. Key Points The relationship between EP El Niño events and the IOD is governed by the El Niño event amplitude The relationship between CP El Niño events and the IOD depends on the El Niňo zonal location The El Niño/IOD relationship experienced a remarkable change due to an ENSO regime shift