El Niño Diversity Across Boreal Spring Predictability Barrier

El Niño exerts widespread hydroclimate impacts during boreal summer. However, the current prediction of El Niño across boreal spring has the most severe forecast errors, partially due to the lack of understanding diversified El Niño onset and decay. Here we show, through nonlinear k-means cluster analysis of evolutions of 40 El Niño events since 1870, El Niño exhibits complex and diverse flavors in its onset and decay across boreal spring predictability barrier. We detected three types of El Niño onset and three types of decay. Each type exhibits distinct coupled dynamics, precursors, and hydroclimate impacts. The results guide the prediction of different types of El Niño transition amid spring predictability barrier and global land precipitation during early and late boreal summer. The new classification offers a metric to evaluate performances of climate models and to project future change of El Niño properties and its predictability.