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Although the Indian Ocean dipole (IOD) and ENSO are significantly correlated, there are indeed some IODs independent of ENSO. In this research, the characteristics of independent IOD are investigated and a new triggering mechanism is proposed based on case study and statistical analysis. Results show that the independent IODs peak in an earlier season and have a weaker intensity compared with the IODs associated with ENSO. The wind anomaly associated with the independent IOD is very unique and shows a monsoonlike pattern, in addition to the equatorial easterly wind anomaly (EEWA) common to all IODs. The evolution of the EEWA associated with the independent IOD is well captured by the second EOF mode of the equatorial zonal wind interannual variability, suggesting that the independent IOD is an important climate mode inherent to the tropical Indian Ocean. The EEWA associated with the independent IOD is tightly linked to Indian summer monsoon activities in spring, and the convection anomalies associated with early summer monsoon onset in the Bay of Bengal plays a key role in inducing the EEWA. The EEWA can persist through spring and summer and causes a series of processes similar to those related to the IODs associated with ENSO. The correlation between the independent IOD and Indian summer monsoon activities increases dramatically after the 1980s, which is probably due to the mean state change in the tropical Indian Ocean climate system. [ABSTRACT FROM AUTHOR]

Abstract: Influence of the Indian Ocean Dipole (IOD) on the Indian Ocean Meridional Heat Transport (MHT) is studied using 60-yr SODA data. Results show that there is anomalous heat transport from the equatorial region to higher latitudes in both hemispheres during IOD events, and the anomalous poleward MHT occurs mainly in the western Indian Ocean. IOD has strong influence on the MHT during late summer and fall, which is consistent with the seasonal phase-locking characteristics of IOD itself. The MHT anomaly caused by anomalous meridional velocity, which is induced by wind, is the major contributor of the total MHT anomalies. EOF analysis shows that the IOD is a key factor for interannual variability of the MHT in the Indian Ocean. These findings are very useful for understanding the Indian Ocean heat balance and climatic implications of IOD. [Copyright &y& Elsevier]