The role of mean state on changes in El Niño's flavor

Jung Choi, Soon Il An, Jong Seong Kug, Sang Wook Yeh

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

Recently, many studies have argued for the existence of two types of El Niño phenomena based on different spatial distributions: the conventional El Niño [or Eastern Pacific (EP) El Niño], and the Central Pacific (CP) El Niño. Here, we investigate the decadal modulation of CP El Niño occurrences using a long-term coupled general circulation model simulation, focusing, in particular, on the role of climate state in the regime change between more and fewer CP El Niño events. The higher occurrence regime of the CP El Niño coincides with the lower occurrence regime of EP El Niño, and vice versa. The climate states associated with these two opposite regimes resemble the leading principal component analysis (PCA) modes of tropical Pacific decadal variability, indicating that decadal change in climate state may lead to regime change in terms of two different types of El Niño. In particular, the higher occurrence regime of CP El Niño is associated with a strong zonal gradient of mean surface temperature in the equatorial Pacific, along with a strong equatorial Trade wind over the area east of the dateline. In addition, the oceanic variables-the mixed layer depth and the thermocline depth-show values indicating increased depth over the western-to-central Pacific. The aforementioned climate states obviously intensify zonal advective feedback, which promotes increased generation of the CP El Niño. Frequent CP El Niño occurrences are not fully described by oceanic subsurface dynamics, and dynamical or thermodynamical processes in the ocean mixed layer and air-sea interaction are important contributors to the generation of the CP El Niño. Furthermore, the atmospheric response with respect to the SSTA tends to move toward the west, which leads to a weak air-sea coupling over the eastern Pacific. These features could be regarded as evidence that the climate state can provide a selection mechanism of the El Niño type.

Original languageEnglish
Pages (from-to)1205-1215
Number of pages11
JournalClimate Dynamics
Volume37
Issue number5
DOIs
Publication statusPublished - 2011 Sep 1

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climate
mixed layer
atmosphere-ocean coupling
air-sea interaction
trade wind
thermocline
general circulation model
principal component analysis
surface temperature
spatial distribution
ocean
simulation

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Choi, Jung ; An, Soon Il ; Kug, Jong Seong ; Yeh, Sang Wook. / The role of mean state on changes in El Niño's flavor. In: Climate Dynamics. 2011 ; Vol. 37, No. 5. pp. 1205-1215.
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abstract = "Recently, many studies have argued for the existence of two types of El Ni{\~n}o phenomena based on different spatial distributions: the conventional El Ni{\~n}o [or Eastern Pacific (EP) El Ni{\~n}o], and the Central Pacific (CP) El Ni{\~n}o. Here, we investigate the decadal modulation of CP El Ni{\~n}o occurrences using a long-term coupled general circulation model simulation, focusing, in particular, on the role of climate state in the regime change between more and fewer CP El Ni{\~n}o events. The higher occurrence regime of the CP El Ni{\~n}o coincides with the lower occurrence regime of EP El Ni{\~n}o, and vice versa. The climate states associated with these two opposite regimes resemble the leading principal component analysis (PCA) modes of tropical Pacific decadal variability, indicating that decadal change in climate state may lead to regime change in terms of two different types of El Ni{\~n}o. In particular, the higher occurrence regime of CP El Ni{\~n}o is associated with a strong zonal gradient of mean surface temperature in the equatorial Pacific, along with a strong equatorial Trade wind over the area east of the dateline. In addition, the oceanic variables-the mixed layer depth and the thermocline depth-show values indicating increased depth over the western-to-central Pacific. The aforementioned climate states obviously intensify zonal advective feedback, which promotes increased generation of the CP El Ni{\~n}o. Frequent CP El Ni{\~n}o occurrences are not fully described by oceanic subsurface dynamics, and dynamical or thermodynamical processes in the ocean mixed layer and air-sea interaction are important contributors to the generation of the CP El Ni{\~n}o. Furthermore, the atmospheric response with respect to the SSTA tends to move toward the west, which leads to a weak air-sea coupling over the eastern Pacific. These features could be regarded as evidence that the climate state can provide a selection mechanism of the El Ni{\~n}o type.",
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The role of mean state on changes in El Niño's flavor. / Choi, Jung; An, Soon Il; Kug, Jong Seong; Yeh, Sang Wook.

In: Climate Dynamics, Vol. 37, No. 5, 01.09.2011, p. 1205-1215.

Research output: Contribution to journalArticle

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