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 language | English (US) |
|---|---|
| Pages (from-to) | 769-783 |
| Number of pages | 15 |
| Journal | Journal of Climate |
| Volume | 27 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 2014 |
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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 journal › Article
}
TY - JOUR
T1 - The south pacific meridional mode
T2 - A mechanism for ENSO-like variability
AU - Zhang, Honghai
AU - Clement, Amy C
AU - Nezio, Pedro Di
PY - 2014/1
Y1 - 2014/1
N2 - 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.
AB - 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.
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U2 - 10.1175/JCLI-D-13-00082.1
DO - 10.1175/JCLI-D-13-00082.1
M3 - Article
VL - 27
SP - 769
EP - 783
JO - Journal of Climate
JF - Journal of Climate
SN - 0894-8755
IS - 2
ER -