El Niño flavors, their interdecadal changes, and impacts on the Indian Ocean Dipole pattern

El Niño events display a large diversity in terms of spatial pattern, temporal evolution, and amplitude, which may change over time due to climate change or internal variability. We used the Extended Reconstructed Sea Surface Temperature (SST), version 5 (ERSSTv5) dataset and applied a nonlinear K-means cluster analysis to the evolution of SST anomalies in the equatorial Pacific for 33 El Niño years from 1901 to 2020. Based on the analysis of the spatio-temporal evolution of El Niño events, we identified 4 types of El Niño, which include basin-wide, eastern Pacific (EP), central Pacific (CP), and successive El Niño. EP and CP El Niño events are weaker and terminate faster than basin-wide El Niño, whereas successive El Niño events are often (83 \(\%\) $\%$ ) followed by a La Niña event. The frequency of basin-wide and particularly CP El Niño events has started to increase since the mid-1950s, while a gradual decrease in the frequency of both EP and successive El Niño is identified during the study period. We have analyzed the linkage between the identified 4 types of El Niño and the Indian Ocean Dipole (IOD). A statistically significant positive correlation is found between basin-wide El Niño and the IOD in boreal autumn, implying that a developing basin-wide El Niño generally can trigger a positive IOD in boreal autumn. Our results have important implications for a better understanding of interdecadal changes in the type of El Niño events and provide a framework to improve the predictability of the IOD.