Decadal variability of Asian--Australian monsoon--ENSO-TBO relationships

Namely, a strong Asian-Australian monsoon is often associated with negative SST anomalies in the equatorial eastern Pacific and a negative Indian Ocean dipole in northern fall between the strong Indian monsoon and strong Australian monsoon, and tends to be followed by a weak monsoon and positive SST anomalies in the Pacific the following year and so on.

These connections are communicated through the large-scale east-west (Walker) circulation that involves the full depth of the troposphere. However, the Asia-Pacific climate system is characterized by intermittent decadal fluctuations whereby the TBO during some time periods is more pronounced than others. Observations and models are analyzed to identify processes that make the system less biennial at certain times due to one or some combination of the following: 1. increased latitudinal extent of Pacific trade winds and wider cold tongue; 2. warmer tropical Pacific compared to tropical Indian Ocean that weakens trade winds and reduces coupling strength; 3. eastward shift of the Walker circulation; 4. reduced interannual variability of Pacific and/or Indian Ocean SSTs.