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The Definition of El Nio

The Definition of El Nio A review is given of the meaning of the term El Nio and how it has changed in time, so there is no universal single definition. This needs to be recognized for scientific uses, and precision can only be achieved if the particular definition is identified in each use to reduce the possibility of misunderstanding. For quantitative purposes, possible definitions are explored that match the El Nios identified historically after 1950, and it is suggested that an El Nio can be said to occur if 5-month running means of sea surface temperature (SST) anomalies in the Nio 3.4 region (5N5S, 120170W) exceed 0.4C for 6 months or more. With this definition, El Nios occur 31 of the time and La Nias (with an equivalent definition) occur 23 of the time. The histogram of Nio 3.4 SST anomalies reveals a bimodal character. An advantage of such a definition is that it allows the beginning, end, duration, and magnitude of each event to be quantified. Most El Nios begin in the northern spring or perhaps summer and peak from November to January in sea surface temperatures. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Bulletin of the American Meteorological Society American Meteorological Society

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References (10)

Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0477
DOI
10.1175/1520-0477(1997)078<2771:TDOENO>2.0.CO;2
Publisher site
See Article on Publisher Site

Abstract

A review is given of the meaning of the term El Nio and how it has changed in time, so there is no universal single definition. This needs to be recognized for scientific uses, and precision can only be achieved if the particular definition is identified in each use to reduce the possibility of misunderstanding. For quantitative purposes, possible definitions are explored that match the El Nios identified historically after 1950, and it is suggested that an El Nio can be said to occur if 5-month running means of sea surface temperature (SST) anomalies in the Nio 3.4 region (5N5S, 120170W) exceed 0.4C for 6 months or more. With this definition, El Nios occur 31 of the time and La Nias (with an equivalent definition) occur 23 of the time. The histogram of Nio 3.4 SST anomalies reveals a bimodal character. An advantage of such a definition is that it allows the beginning, end, duration, and magnitude of each event to be quantified. Most El Nios begin in the northern spring or perhaps summer and peak from November to January in sea surface temperatures.

Journal

Bulletin of the American Meteorological SocietyAmerican Meteorological Society

Published: Dec 1, 1997

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