The Linear Response of ENSO to the Madden–Julian Oscillation

Zavala‐Garay, Javier; Zhang, C.; Moore, Andrew M.; Kleeman, Richard

doi:10.1175/jcli3408.1

Cited by 88 publications

(66 citation statements)

References 51 publications

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“…8) is mostly a linear response to the forcing, consistent with the point of view of Roulston and Neelin (2000), who showed that an intermediate complexity coupled model similar to CZ responded mainly to the slow component of stochastic noise forcing, and Zavala-Garay et al (2005), who used an intermediate complexity model and found that ENSO responds linearly to the lowfrequency power of the MJO. In the stochastic WWB case, however, the WWB energy is far less peaked in the interannual band, and the model appears to be responding nonlinearly to the forcing, rectifying fast WWB variability into slow ENSO amplitude.…”

Section: B Understanding the Different Response To Modulated And Stosupporting

confidence: 77%

“…Note that the WWB events used here are meant to represent the episodic WWBs with a duration of a week or two in the observed record, rather than the intraseasonal scale wind perturbations such as those due to the Madden-Julian oscillation (MJO) whose interactions with ENSO have been studied fairly extensively (e.g., Bergman et al 2001;Kessler 2001;Kessler et al 1995;Zavala-Garay et al 2005). The effects of the MJO on the CZ model were also studied by Zebiak (1989), who found that weak stochastic forcing with power mostly in the 20-60-day band had little effect on model simulations and hindcasts.…”

Section: B Parameterizing Wwb Modulation By Warm Pool Extensionmentioning

confidence: 99%

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Westerly Wind Bursts: ENSO’s Tail Rather than the Dog?

2005

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Westerly wind bursts (WWBs) in the equatorial Pacific occur during the development of most El Niño events and are believed to be a major factor in ENSO's dynamics. Because of their short time scale, WWBs are normally considered part of a stochastic forcing of ENSO, completely external to the interannual ENSO variability. Recent observational studies, however, suggest that the occurrence and characteristics of WWBs may depend to some extent on the state of ENSO components, implying that WWBs, which force ENSO, are modulated by ENSO itself.Satellite and in situ observations are used here to show that WWBs are significantly more likely to occur when the warm pool is extended eastward. Based on these observations, WWBs are added to an intermediate complexity coupled ocean-atmosphere ENSO model. The representation of WWBs is idealized such that their occurrence is modulated by the warm pool extent. The resulting model run is compared with a run in which the WWBs are stochastically applied. The modulation of WWBs by ENSO results in an enhancement of the slow frequency component of the WWBs. This causes the amplitude of ENSO events forced by modulated WWBs to be twice as large as the amplitude of ENSO events forced by stochastic WWBs with the same amplitude and average frequency. Based on this result, it is suggested that the modulation of WWBs by the equatorial Pacific SST is a critical element of ENSO's dynamics, and that WWBs should not be regarded as purely stochastic forcing. In the paradigm proposed here, WWBs are still an important aspect of ENSO's dynamics, but they are treated as being partially stochastic and partially affected by the large-scale ENSO dynamics, rather than being completely external to ENSO.It is further shown that WWB modulation by the large-scale equatorial SST field is roughly equivalent to an increase in the ocean-atmosphere coupling strength, making the coupled equatorial Pacific effectively self-sustained.

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Section: B Understanding the Different Response To Modulated And Stosupporting

confidence: 77%

Section: B Parameterizing Wwb Modulation By Warm Pool Extensionmentioning

confidence: 99%

Westerly Wind Bursts: ENSO’s Tail Rather than the Dog?

2005

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“…While this limits the discussion of linear response of the ocean to low-frequency MJO forcing [Zavala-Garay et al, 2005], it enables us to quantify the contribution of the nonlinear rectification of the intraseasonal MJO forcing. In a previous study, Jiang et al [2009] examined the rectification over 5 years and could not determine whether rectification of the MJO may have influence on ENSO.…”

Section: Summary and Discussionmentioning

confidence: 99%

Tropical Pacific Ocean and the Madden‐Julian Oscillation: Role of wind and buoyancy forcing

Zhang

Thompson

et al. 2010

J. Geophys. Res.

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[1] A global ocean circulation model is used to examine the dynamical response of the tropical Pacific Ocean to forcing associated with the Madden-Julian Oscillation (MJO).Model sensitivity experiments first reveal that MJO-related changes in sea level are caused primarily by changes in wind stress. Further, the MJO-related changes in sea surface temperature (SST) are mainly caused by buoyancy (heat) flux in the Indian Ocean, by wind stress in the central tropical Pacific, and by both buoyancy flux and wind stress in the eastern tropical Pacific. Additional model sensitivity studies quantify the tropical Pacific Ocean response to MJO wind forcing. The simulations reveal that the subsurface temperature variations associated with the MJO propagate eastward along the thermocline and rise to the surface in the eastern Pacific. Zonal advection plays a dominant role in SST variation in the central Pacific; vertical advection plays an important role in the evolution of subsurface and surface temperatures in the eastern Pacific. Finally, it is shown that MJO wind forcing can rectify SST variations through nonlinear interactions of the intraseasonal variations of the zonal currents and the zonal SST gradient.

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“…Daily values of the SST were obtained by interpolation using a linear scheme as in Zavala-Garay et al (2005). The data domain of zonal wind was the whole equatorial strip of the Pacific Ocean from 120°E to 70°W and 15°N to 15°S, which contained most of the convective variability of the Pacific MJO; for SST, we concentrated on the tropical-subtropical Pacific Ocean (20°S to 20°N, 120°E to 70°W), which embodied most of the ENSO SST anomalies.…”

Section: The Data and Analysis Techniquementioning

confidence: 99%

“…When B is an eigenvector, the R and θ represent spatial features of propagating waves, whereas when B is a time series, they characterize the temporal evolution of the propagating waves. More information on HSVD can be found in Barnett (1983) and Zavala-Garay et al (2005).…”

Section: Hilbert Singular Value Decomposition (Hsvd)mentioning

confidence: 99%

An Analysis of Nonlinear Relationship between the MJO and ENSO

Tang

2008

Journal of the Meteorological Society of Japan

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Using the Hilbert Singular Value Decomposition (HSVD) and the Nonlinear Canonical Correlation Analysis (NLCCA), we analyzed the statistical relationship of MJO (Madden-Julian Oscillation) and ENSO (El Niño and Southern Oscillation). It was found that while a linear analysis produced no significant relationship between MJO and ENSO, a low-order nonlinear analysis based on the quadratic function of HSVD led to statistically significant lagged correlations. When their nonlinear relationship was further extracted by the NLCCA, stronger correlation was obtained, with the maximum correlation coefficient appearing while the MJO signals preceding the ENSO signals by around 2 months and 5−6 months respectively. The time lags producing the maximum correlation are respectively consistent with the characteristic time of MJO influencing ENSO dominated by two physical processes: the equatorial Kelvin waves and air-sea feedback. Corresponding to the two different physical processes, ENSO shows different features of development. In the former scenario, the westerly winds in the western Pacific excite the equatorial Kelvin waves which propagate eastward and deepen the thermocline in the eastern Pacific, resulting in the sea surface warming at the far eastern Pacific near the coast. In the latter scenario, the westerly anomalies in the western Pacific precede the development of El Niño through bringing surface warm water into the central and eastern Pacific, thus the sea surface warming occurs across the whole eastern Pacific ocean.

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The Linear Response of ENSO to the Madden–Julian Oscillation

Cited by 88 publications

References 51 publications

Westerly Wind Bursts: ENSO’s Tail Rather than the Dog?

Westerly Wind Bursts: ENSO’s Tail Rather than the Dog?

Tropical Pacific Ocean and the Madden‐Julian Oscillation: Role of wind and buoyancy forcing

An Analysis of Nonlinear Relationship between the MJO and ENSO

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