The south pacific meridional mode

A mechanism for ENSO-like variability

Honghai Zhang, Amy C Clement, Pedro Di Nezio

Research output: Contribution to journalArticle

72 Citations (Scopus)

Abstract

In this study, the authors investigate the connection between the South Pacific atmospheric variability and the tropical Pacific climate in models of different degrees of coupling between the atmosphere and ocean. A robust mode of variability, defined as the South Pacific meridional mode (SPMM), is identified in a multimodel ensemble of climate model experiments where the atmosphere is only thermodynamically coupled to a slab ocean mixed layer. The physical interpretation of the SPMM is nearly identical to the North Pacific meridional mode (NPMM) with the off-equatorial southeast trade wind variability altering the latent heat flux and sea surface temperature (SST) and initiating a wind-evaporation-SST feedback that propagates signals into the tropics. The authors also show that a positive cloud feedback plays a role in the development of this mode, but this effect is model dependent. While physically analogous to the NPMM, theSPMMhas a stronger expression in the equatorial Pacific and directly perturbs the zonal gradients of SST and sea level pressure (SLP) on the equator, thus leading to ENSO-like variability despite the lack of ocean-atmosphere dynamical coupling. Further analysis suggests that the SPMM is also active in fully coupled climate models and observations. This study highlights the important role of the Southern Hemisphere in tropical climate variability and suggests that including observations from the data-poor South Pacific could improve the ENSO predictability.

Original languageEnglish (US)
Pages (from-to)769-783
Number of pages15
JournalJournal of Climate
Volume27
Issue number2
DOIs
StatePublished - Jan 2014

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El Nino-Southern Oscillation
sea surface temperature
climate modeling
atmosphere-ocean coupling
atmosphere
trade wind
ocean
sea level pressure
latent heat flux
mixed layer
Southern Hemisphere
slab
evaporation
climate
experiment
effect
tropical climate
tropics
analysis

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

The south pacific meridional mode : A mechanism for ENSO-like variability. / Zhang, Honghai; Clement, Amy C; Nezio, Pedro Di.

In: Journal of Climate, Vol. 27, No. 2, 01.2014, p. 769-783.

Research output: Contribution to journalArticle

Zhang, Honghai ; Clement, Amy C ; Nezio, Pedro Di. / The south pacific meridional mode : A mechanism for ENSO-like variability. In: Journal of Climate. 2014 ; Vol. 27, No. 2. pp. 769-783.
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