Assessment of the impacts of the 1997-98 El Nino on the Asian-Australia monsoon

Singular Value Decomposition (SVD) analyses of rainfall and sea surface temperature (SST) are carried out globally over the entire tropics and regionally over the Asia-Australian (AA)-monsoon domain. Contributions to monsoon rainfall predictability by basin-scale SST forcing and regional SST coupling are evaluated from cumulative anomaly correlation with dominant regional SVD modes. The observed 1997-98 AA-monsoon anomalies are found to be very complex with approximately 34% of the anomalies of the Asian (boreal) summer monsoon and 74% of the Australia (austral) monsoon attributable to basin-scale SST influence associated with El Nino. For the boreal and austral monsoon respectively, regional coupled processes contribute an additional 19% and 10%, leaving about 47% and 16% due to other factors including high frequency transients. Results suggest that in order to improve seasonal-to-interannual predictability of the AA-monsoon, we need to investigate and exploit not only monsoon-Fl Nino relationship, but also intrinsic monsoon regional coupled processes.