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Open Access Publications from the University of California

Identifying the types of major El Niño events since 1870

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This study develops a pattern correlation method to determine the type of major El Niño events since 1870 from a reconstructed sea surface temperature dataset. Different from other identification methods, this method allows an El Niño event to be of the Central-Pacific (CP) type, the Eastern-Pacific (EP) type, or the Mixed type (i.e. the both types coexist). Application of this method to the 39 major El Niño events identified by the Ocean Niño Index during the period 1870–2010 results in 8 events that are categorized to be of the EP type, 16 of the CP type, and 15 of Mixed type. Before the 1910s, the El Niño events are mostly of the EP type, but are mostly the CP type after 2000, while in between both types occurred. The consistencies and inconsistencies between the El Niño types identified by this method and other three methods, which have been proposed recently for El Niño-type classification, are examined and discussed. All four methods consistently identify the El Niño events occurring in the following years to be of the EP types: 1876–1877, 1881, 1884–1885, 1895–1896, 1896–1897, 1918–1919, 1982–1983, and 1997–1998; and the events occurring in the following years to be of the CP type: 1968–1969, 1977–1978, 1994–1995, 2004–2005, and 2009–2010. It is evident that the characteristics of the EP type of El Niño are more robust in the 19th century and the early part of the 20th century, whereas the characteristics of the CP type of El Niño is more robust in the late 20th century and the early 21st century. The list of the El Niño types produced by this study can be used for selecting El Niño events to further study the dynamics and climate impacts of the EP, CP, and Mixed types of El Niño.

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