La Ni?a's Teleconnection to the Indian Ocean Dipole Controlled by Its Longitudinal Position

While the prominent influence of El Nino-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 Nino exhibit distinct associations with the IOD. In this study, we demonstrate that La Nina's teleconnection to the IOD is primarily controlled by its longitudinal position. Westward-displaced La Nina 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 Nina 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 Nina's longitudinal position on the IOD's response is realistically reproduced by targeted pacemaker experiments, providing new insights into inter-basin climate connections. The tropical Indian Ocean usually witnesses a dipolar pattern of sea surface temperature (SST) anomalies, which is commonly referred to as the Indian Ocean Dipole (IOD). The IOD phenomenon has received much attention due to its profound global impacts, yet its seasonal prediction remains a large challenge for the climate community. The year-to-year variability of IOD has usually been linked to the El Nino-Southern Oscillation (ENSO), the predominant interannual climate variability in the tropical Pacific. The relationship between El Nino (i.e., warm phase of ENSO) and the intensity of IOD has been demonstrated in previous studies, which is shown to be dependent on the different El Nino flavors. In this study, we show that the longitudinal position of negative SST anomalies during La Nina events (i.e., cold phase of ENSO) in shaping their connection with IOD. Different from westward-displaced La Nina events that can drive robust negative IOD events, eastward-displaced La Nina events do not yield significant IOD anomalies due to the excessively cold conditions prevalent in the eastern Pacific cold tongue region. We highlight the importance of La Nina's longitudinal position in its teleconnection to other ocean basins and the associated regional climate anomalies. The La Nina's regulation of Indian Ocean Oscillation (IOD) mainly depends on the La Nina longitudinal position The westward-displaced La Nina events produce significant Walker Circulation anomalies, triggering robust negative IOD event The importance of La Nina longitudinal position on the IOD's response can be evidenced by the targeted pacemaker experiments