On the low western Pacific sea levels observed prior to strong East Pacific El Niños

<p>Research, based on both observations and ocean models, has indicated that strong East Pacific El Niños are preceded by the development of unusually low sea levels at the western end of the North Equatorial Trough early in the year. This results in an increase in the strength of the North Eq...

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Autor principal:	D. J. Webb
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Geography. Anthropology. Recreation G Environmental sciences GE1-350
Acceso en línea:	https://doaj.org/article/5529bf12ad004ce7bc6243d1c9aea0b9
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spelling	oai:doaj.org-article:5529bf12ad004ce7bc6243d1c9aea0b92021-11-08T10:37:37ZOn the low western Pacific sea levels observed prior to strong East Pacific El Niños10.5194/os-17-1585-20211812-07841812-0792https://doaj.org/article/5529bf12ad004ce7bc6243d1c9aea0b92021-11-01T00:00:00Zhttps://os.copernicus.org/articles/17/1585/2021/os-17-1585-2021.pdfhttps://doaj.org/toc/1812-0784https://doaj.org/toc/1812-0792<p>Research, based on both observations and ocean models, has indicated that strong East Pacific El Niños are preceded by the development of unusually low sea levels at the western end of the North Equatorial Trough early in the year. This results in an increase in the strength of the North Equatorial Counter Current which, aided by low sea levels due to the annual Rossby wave, then transports West Pacific Warm Pool water to the central and eastern Pacific.</p> <p>Here, an ocean model is used to investigate the factors affecting sea level prior to the 1982–1983 East Pacific El Niño. The results indicate that during this period the reduction in sea level was caused by Ekman pumping, due to the local winds, acting over a period of many months. The north–south distances involved mean that such upwelling can be connected to the westerly wind phase of Madden–Julian Oscillations.</p> <p>Since the 1980s, the quality and quantity of global wind measurement has steadily improved. So, if the Ekman pumping hypothesis is correct, the better-quality wind data available prior to the 1997–1998 and 2015–2016 East Pacific El Niños should also show unusually large Ekman pumping in the same region, over a similar long period. This is tested and found to be correct.</p> <p>However, a study of the integrated Ekman pumping for the period 1976 to 2015 indicates that in some years similar events did not develop despite a comparable amount of pumping during the first part of the year. The results imply that significant Ekman pumping early in the year is a necessary but not sufficient requirement for the development of a strong East Pacific El Niño.</p>D. J. WebbCopernicus PublicationsarticleGeography. Anthropology. RecreationGEnvironmental sciencesGE1-350ENOcean Science, Vol 17, Pp 1585-1604 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Geography. Anthropology. Recreation G Environmental sciences GE1-350
spellingShingle	Geography. Anthropology. Recreation G Environmental sciences GE1-350 D. J. Webb On the low western Pacific sea levels observed prior to strong East Pacific El Niños
description	<p>Research, based on both observations and ocean models, has indicated that strong East Pacific El Niños are preceded by the development of unusually low sea levels at the western end of the North Equatorial Trough early in the year. This results in an increase in the strength of the North Equatorial Counter Current which, aided by low sea levels due to the annual Rossby wave, then transports West Pacific Warm Pool water to the central and eastern Pacific.</p> <p>Here, an ocean model is used to investigate the factors affecting sea level prior to the 1982–1983 East Pacific El Niño. The results indicate that during this period the reduction in sea level was caused by Ekman pumping, due to the local winds, acting over a period of many months. The north–south distances involved mean that such upwelling can be connected to the westerly wind phase of Madden–Julian Oscillations.</p> <p>Since the 1980s, the quality and quantity of global wind measurement has steadily improved. So, if the Ekman pumping hypothesis is correct, the better-quality wind data available prior to the 1997–1998 and 2015–2016 East Pacific El Niños should also show unusually large Ekman pumping in the same region, over a similar long period. This is tested and found to be correct.</p> <p>However, a study of the integrated Ekman pumping for the period 1976 to 2015 indicates that in some years similar events did not develop despite a comparable amount of pumping during the first part of the year. The results imply that significant Ekman pumping early in the year is a necessary but not sufficient requirement for the development of a strong East Pacific El Niño.</p>
format	article
author	D. J. Webb
author_facet	D. J. Webb
author_sort	D. J. Webb
title	On the low western Pacific sea levels observed prior to strong East Pacific El Niños
title_short	On the low western Pacific sea levels observed prior to strong East Pacific El Niños
title_full	On the low western Pacific sea levels observed prior to strong East Pacific El Niños
title_fullStr	On the low western Pacific sea levels observed prior to strong East Pacific El Niños
title_full_unstemmed	On the low western Pacific sea levels observed prior to strong East Pacific El Niños
title_sort	on the low western pacific sea levels observed prior to strong east pacific el niños
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/5529bf12ad004ce7bc6243d1c9aea0b9
work_keys_str_mv	AT djwebb onthelowwesternpacificsealevelsobservedpriortostrongeastpacificelninos
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On the low western Pacific sea levels observed prior to strong East Pacific El Niños

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