La Niña's Teleconnection to the Indian Ocean Dipole Controlled by Its Longitudinal Position

Abstract

While the prominent influence of El Niño-Southern Oscillation (ENSO) on the Indian Ocean Oscillation (IOD) is widely recognized, intricate relationships between them are often invoked that introduce challenges into seasonal predictions. Previous studies have shown that different flavors of El Niño exhibit distinct associations with the IOD. In this study, we demonstrate that La Niña's teleconnection to the IOD is primarily controlled by its longitudinal position. Westward-displaced La Niña events tend to produce stronger negative convection anomalies in the central Pacific and more pronounced Walk Circulation anomalies, thereby triggering strong negative IOD events. In contrast, eastward-displaced La Niña events are usually accompanied by feeble convection response due to the excessively cold conditions in the cold tongue, yielding insignificant IOD response. The pivotal role of La Niña's longitudinal position on the IOD's response is realistically reproduced by targeted pacemaker experiments, providing new insights into inter-basin climate connections.