Rectification of the Enso Variability by Interdecadal Changes in the Equatorial Background Mean State in a CGCM Simulation

Dewitte, Boris; Yeh, Sang‐Wook; Cibot, Carole; Terray, Laurent

doi:10.4067/s0717-65382004000200028

Cited by 9 publications

(34 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The classical 'linear' model links ENSO variability with the zonal gradient through the 'destabilizing' effect of cold thermocline waters of the Eastern Pacific but produced the opposite relationship [10][11][12] (for example, positive instead of negative correlation) compared with the results of our study. Another mechanism linking ENSO variability and SST zonal gradient is based on external forcing of one of several feedbacks within the ENSO system during a particular season 13,14 .…”

Section: Discussionsupporting

confidence: 63%

“…Analysing ENSO data from observations and modelling experiments, he found 10-20-year cycles within the ENSO system, which can be described as alternating periods of enhanced ENSO variability and decreased zonal gradient with periods of subdued ENSO variability and increased zonal gradient. These decadal changes were attributed to the nonlinear dynamics of the ENSO system 12,18,19 . The nonlinear dynamic may be important for interpreting our results because the total variability reconstructed using proxy data represents a millennial average and consequently includes multiple components of ENSO variability.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Palaeoclimate reconstructions reveal a strong link between El Niño-Southern Oscillation and Tropical Pacific mean state

et al. 2013

View full text Add to dashboard Cite

The El Niño-Southern Oscillation (ENSO) is one of the most important components of the global climate system, but its potential response to an anthropogenic increase in atmospheric CO 2 remains largely unknown. One of the major limitations in ENSO prediction is our poor understanding of the relationship between ENSO variability and long-term changes in Tropical Pacific oceanography. Here we investigate this relationship using palaeorecords derived from the geochemistry of planktonic foraminifera. Our results indicate a strong negative correlation between ENSO variability and zonal gradient of sea-surface temperatures across the Tropical Pacific during the last 22 ky. This strong correlation implies a mechanistic link that tightly couples zonal sea-surface temperature gradient and ENSO variability during large climate changes and provides a unique insight into potential ENSO evolution in the future by suggesting enhanced ENSO variability under a global warming scenario.

show abstract

Section: Discussionsupporting

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Palaeoclimate reconstructions reveal a strong link between El Niño-Southern Oscillation and Tropical Pacific mean state

et al. 2013

View full text Add to dashboard Cite

show abstract

“…The underlying idea behind this hypothesis is that changes in equatorial stratification as measured by changes in the baroclinic mode energy distribution could explain some aspect of the ENSO amplitude modulation. Recent results (i.e., Dewitte et al 2006) based on the analysis of a coupled general circulation model (CGCM) simulation support this hypothesis. The source of the change in baroclinic energy distribution remains, however, unclear due in part to the biases in simulated mean state as observed in many CGCMs.…”

Section: Introductionmentioning

confidence: 54%

“…For instance in the CGCM of Cibot et al (2005), the thermocline decadal mode associated with the ENSO modulation has a center of action both in the South Central Pacific and along the equator, and is forced through Ekman pumping associated with the ENSO modulation. The equatorial component of this mode is able to produce changes in ENSO on low frequencies through the nonlinear equatorial dynamics (Dewitte et al 2006). No equatorward propagation of subsurface temperature anomalies from the South-Western Pacific could be observed.…”

Section: Introductionmentioning

confidence: 98%

“…Because of these biases the simulated ENSO mode in CGCMs usually tends to resemble the theoretical 'ocean basin mode' (Neelin and Jin 1993;An and Jin 2000) due to weak upwelling feedback loop in the eastern tropical Pacific (van Oldenborg et al 2005). This in particular leads to over energetic ENSO variability in the quasi-biennial band (AchutaRao et al 2004;Guilyardi et al 2004;Rodgers et al 2004;Dewitte et al 2006). Because the processes leading to ENSO modulation may involve the interaction with the mean state, it is important to rely on CGCMs that simulate it with some degree of realism.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Source of low frequency modulation of ENSO amplitude in a CGCM

et al. 2007

Self Cite

View full text Add to dashboard Cite

We study the relationship between changes in equatorial stratification and low frequency El Niñ o/ Southern Oscillation (ENSO) amplitude modulation in a coupled general circulation model (CGCM) that uses an anomaly coupling strategy to prevent climate drifts in the mean state. The stratification is intensified at upper levels in the western and central equatorial Pacific during periods of high ENSO amplitude. Furthermore, changes in equatorial stratification are connected with subsurface temperature anomalies originating from the central south tropical Pacific. The correlation analysis of ocean temperature anomalies against an index for the ENSO modulation supports the hypothesis of the existence of an oceanic ''tunnel'' that connects the south tropical Pacific to the equatorial wave guide. Further analysis of the wind stress projection coefficient onto the oceanic baroclinic modes suggests that the low frequency modulation of ENSO amplitude is associated with a significant contribution of higher-order modes in the western and central equatorial Pacific. In the light of these results, we suggest that, in the CGCM, change in the baroclinic mode energy distribution associated with low frequency ENSO amplitude modulation have its source in the central south tropical Pacific.

show abstract

The Central Pacific El Niño intraseasonal Kelvin wave

2014

View full text Add to dashboard Cite

In this study, we document and interpret the characteristics of the IntraSeasonal Kelvin wave (ISKw) in the Pacific over the 1989-2011 period, based on observations, a linear model, and the outputs of an Ocean General Circulation Model (OGCM). We focus on the wave activity during the Central Pacific (CP) El Niño events contrasting with the extraordinary El Niño of 1997/1998. We find that the ISKw activity is enhanced in Austral summer (spring) in the central Pacific (west of 120 W) during CP El Niño events. The linear model experiment indicates that the Austral summer peak is wind-forced, while the Austral spring peak is not and consequently results from nonlinear processes. In addition, a strong dissipation of the ISKws is observed east of 120 W which cannot be accounted for by a linear model using a Rayleigh friction. A vertical and horizontal mode decomposition of the OGCM simulation further confirms the sharp changes in characteristics of the ISKws as well as the reflection of the latter into first-meridional Rossby wave at the longitude where the maximum zonal gradient of the thermocline is found (120 W). Our analysis suggests that the confinement of CP El Niño warming in the central Pacific may result from the reinforcement of the zonal gradient in stratification associated with the La Niña-like conditions since the late of the 1990s, leading to scattering of the energy of the ISKws in the eastern Pacific.

show abstract

Rectification of the Enso Variability by Interdecadal Changes in the Equatorial Background Mean State in a CGCM Simulation

Cited by 9 publications

References 35 publications

Palaeoclimate reconstructions reveal a strong link between El Niño-Southern Oscillation and Tropical Pacific mean state

Palaeoclimate reconstructions reveal a strong link between El Niño-Southern Oscillation and Tropical Pacific mean state

Source of low frequency modulation of ENSO amplitude in a CGCM

The Central Pacific El Niño intraseasonal Kelvin wave

Contact Info

Product

Resources

About