Different Types of El Niño Transition Processes One Year after Its Occurrence

Understanding the transition processes of El Niño events is important because such events cause abnormal atmospheric variabilities worldwide, including extreme weather events, for one year following their occurrence. In this study, we examined the different types of such transition processes based on observations and two multi-century model simulations. One type is characterized by a quick transition from an El Niño event into a La Niña event in the following winter, and the other type involves a slow decay to an almost neutral state or a successive occurrence of El Niño event. We found that surface wind anomalies in the central to eastern subtropical Pacific and the associated sea surface temperature (SST) anomalies during boreal early winter in the Northern Hemisphere play important roles in determining the different types of El Niño transition processes through atmosphere-ocean coupled processes in the early spring and summer that follow the event. This provides potential precursors for predicting the occurrence of a La Niña event, a neutral state, and an El Niño event one year after the occurrence of an El Niño event. Similar transition processes were also found in two multi-century model simulations.