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On the role of the North Equatorial Counter Current during a strong El Niño

On the role of the North Equatorial Counter Current during a strong El Niño
On the role of the North Equatorial Counter Current during a strong El Niño
An analysis of archived data from the NEMO 1∕12th degree global ocean model shows the importance of the North Equatorial Counter Current (NECC) in the development of the strong 1982–1983 and 1997–1998 El Niños. The model results indicate that in a normal year the core of warm water in the NECC is diluted by the surface Ekman transport, by geostrophic inflow and by tropical instability waves. During the development of the 1982–1983 and 1997–1998 El Niños, these processes had reduced effect at the longitudes of warmest equatorial temperatures and to the west. During the autumns of 1982 and 1997, the speed of the NECC was also increased by a stronger-than-normal annual Rossby wave. The increased transport of warm water by the NECC due to these changes resulted in warm water reaching the far eastern Pacific and appears to have been a major factor in moving the centre of deep atmospheric convection eastwards across the Pacific.
1812-0792
633-660
Webb, David John
152e6ec6-b96b-481d-968b-4293e7bd82c5
Webb, David John
152e6ec6-b96b-481d-968b-4293e7bd82c5

Webb, David John (2018) On the role of the North Equatorial Counter Current during a strong El Niño. Ocean Science, 14 (4), 633-660. (doi:10.5194/os-14-633-2018).

Record type: Article

Abstract

An analysis of archived data from the NEMO 1∕12th degree global ocean model shows the importance of the North Equatorial Counter Current (NECC) in the development of the strong 1982–1983 and 1997–1998 El Niños. The model results indicate that in a normal year the core of warm water in the NECC is diluted by the surface Ekman transport, by geostrophic inflow and by tropical instability waves. During the development of the 1982–1983 and 1997–1998 El Niños, these processes had reduced effect at the longitudes of warmest equatorial temperatures and to the west. During the autumns of 1982 and 1997, the speed of the NECC was also increased by a stronger-than-normal annual Rossby wave. The increased transport of warm water by the NECC due to these changes resulted in warm water reaching the far eastern Pacific and appears to have been a major factor in moving the centre of deep atmospheric convection eastwards across the Pacific.

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Accepted/In Press date: 22 June 2018
e-pub ahead of print date: 11 July 2018

Identifiers

Local EPrints ID: 424805
URI: http://eprints.soton.ac.uk/id/eprint/424805
ISSN: 1812-0792
PURE UUID: 534e7c1d-431c-4e8b-94ea-f4a1def75207

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Date deposited: 05 Oct 2018 11:47
Last modified: 27 Apr 2022 04:27

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Author: David John Webb

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