[A-CG43] Multi-scale ocean-atmosphere interaction in the tropics

[ACG43-03] La Niña Modoki and diversity of coastal El Niño events

*野口 智哉¹、東塚 知己¹ (1.東京大学)

キーワード：沿岸エルニーニョ、ラニーニャもどき、太平洋赤道域

Coastal El Niño events are associated with anomalously warm sea surface temperatures along the coast of South America and can cause flood damage in the coastal areas. While understanding their mechanisms is crucial, past research has mostly focused on individual events, without identifying their general characteristics. This study classifies coastal El Niño events into two types based on whether they develop into basin-scale El Niño and examines why some coastal El Niño events develop and decay locally, without evolving into basin-scale El Niño events. Observational data analysis reveals that coastal El Niño events that occur under a La Niña Modoki condition do not develop into basin-scale El Niño. This may be attributed to equatorial upwelling Kelvin waves induced by easterly wind anomalies to the west of negative SST anomalies that eventually reach the South American coast. Sensitivity experiments using a regional ocean model further support this finding.