In this framework, ENSO complexity is linked to two key coupling mechanisms in the tropical and extratropical Pacific. The interplay of these processes can explain how the different ENSO evolution (episodes, cycles, and multi-year events) are produced. The study finds the extratropical coupling process works to increase ENSO complexity while the tropical coupling process acts to reduce the complexity. The framework proposed in this study can also explain why the properties of El Niño and La Niña can be asymmetric to each other.
This talk will also discuss the reason why the extratropical coupling process can increase the ENSO complexity and El Niño-La Niña asymmetries as well as the application of this ENSO complexity framework in climate model evaluations.