Oral

IAMAS

JMP09 - El Nino/Southern Oscillation and its Global and Regional Impacts

Understanding the Driving Mechanisms behind Triple-Dip La Ninas: Insights from the Prediction Perspective

This study investigates the mechanisms and predictability of consecutive La Ni?a events, focusing on the 1998?2001 and 2020?2023 triple-dip events, using a physically based statistical ENSO prediction model (EPM). The results highlight distinct driving mechanisms behind these two events. The 1998?2001 event was primarily initiated by substantial negative heat content anomalies in the equatorial Pacific, which resulted from the preceding strong El Ni?o and sustained cold sea surface temperature anomalies (SSTA) into the third year. In contrast, the 2020?2023 event, lacking significant negative heat content, was characterized by persistent equatorial easterly wind anomalies induced by extratropical forcing from the Southern Hemisphere. The EPM successfully captures these differences, with tropical ocean-atmosphere coupling dominating predictability in 1998?2001, especially during the second year, while extratropical forcing significantly improves forecasts for 2020?2023. Incorporating extratropical influences is crucial for improving the prediction of multi-year La Ni?a events.