Some negative IOD events occur at the same time as La Niña. However, negative IOD events rarely coincide with El Niño. The relationship between La Niña and the IOD is complicated, with the level of dependence between the two an area of active research. The map shows mean rainfall deciles for winter-spring rainfall for the five negative IOD events that coincided with La Niña since 1960.
The map shows that when a negative IOD event and La Niña coincide, winter–spring rainfall has been above average over large parts of Australia. This shift in pattern towards above-average rainfall is in line with the impacts typically expected in La Niña.