A Quasi‐Biennial Oscillation in the equatorial Atlantic Ocean

Tseng, Lishan; Mechoso, Carlos R.

doi:10.1029/2000gl011206

Cited by 7 publications

(4 citation statements)

References 17 publications

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“…Handoh and Bigg (2000) considered that the initiating mechanism of the 1995-1997 EAO was a westerly wind burst in the western tropical Atlantic. However, our analysis suggests that, more typically, westerly wind anomalies over the eastern equatorial Atlantic, are precursors of the EAO, and that STA ENSO-independent events are an internal selfsustaining oscillation of the equatorial Atlantic, supporting the hypotheses proposed by Handoh and Bigg, (2000) and Tseng and Mechoso (2001). Our analysis also supports the idea that such events are independent of ENSO signals.…”

Section: Discussionsupporting

confidence: 83%

See 1 more Smart Citation

Interannual variability of the Tropical Atlantic independent of and associated with ENSO: Part II. The South Tropical Atlantic

Handoh¹,

Bigg²,

Matthews³

et al. 2006

Intl Journal of Climatology

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Two dominant ocean-atmosphere modes of variability on interannual timescales were defined in part I of this work, namely, the North Tropical Atlantic (NTA) and South Tropical Atlantic (STA) modes. In this paper we focus on the STA mode that covers the equatorial and sub-tropical South Atlantic. We show that STA events occurring in conjunction with ENSO have a preference for the southern summer season and seem to be forced by an atmospheric wave train emanating from the central tropical Pacific and travelling via South America, in addition to the more direct ENSO-induced change in the Walker Circulation. They are lagged by one season from the peak of ENSO. These events show little evidence for other-than-localised coupled ocean-atmosphere interaction.In contrast, STA events occurring in the absence of ENSO favour the southern winter season. They appear to be triggered by a Southern Hemisphere wave train emanating from the Pacific sector, and then exhibit features of a selfsustaining climate mode in the tropical Atlantic. The southward shift of the inter tropical convergence zone that occurs during the warm phase of such an event triggers an extra tropical wave train that propagates downstream in the Southern Hemisphere. We present a unified view of the NTA and STA modes through our observational analysis of the interannual tropical Atlantic variability.

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Section: Discussionsupporting

confidence: 83%

“…The largest positive τ x anomalies are located west of those of SST, with weak, negative anomalies of τ x to the east of the SST anomaly maximum. This pattern over the equatorial region was found in previous work (Zebiak, 1993;Handoh and Bigg, 2000;Ruiz-Barradas et al, 2000;Tseng and Mechoso, 2001).…”

Section: Composite Analysissupporting

confidence: 88%

Interannual variability of the Tropical Atlantic independent of and associated with ENSO: Part II. The South Tropical Atlantic

Handoh¹,

Bigg²,

Matthews³

et al. 2006

Intl Journal of Climatology

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“…A2 also exhibits oscillations corresponding to past equatorial Atlantic warm-cold sequential events of 1949-1950, 1967-1971, 1983-1984, and 1996-1997. These types of events are generally not well correlated with El niño events, consistent with a purely internal mode of tropical Atlantic variability on interannual timescales (Handoh and Bigg, 2000;Tseng and Mechoso, 2001).…”

Section: Singular Value Decomposition Analysismentioning

confidence: 88%

“…Interannual variability in the tropical Atlantic is more complex than in the Pacific where El Niño-Southern Oscillation (ENSO) is the single dominant mode of variability. Equatorial warm events, analogous to ENSO, do occur in the Atlantic (Zebiak, 1993) with a quasi-biennial signature (Tourre et al, 1999;Tseng and Mechoso, 2001;Mo and Häkkinen, 2001). These equatorial warm events are maintained by a Bjerknestype feedback involving ocean dynamics (Hirst, 1988;Xie et al, 1999), although their amplitude is much less than in ENSO events in the Pacific.…”

Section: Introductionmentioning

confidence: 99%

Interannual variability of the tropical Atlantic independent of and associated with ENSO: Part I. The North Tropical Atlantic

Handoh

Matthews

Bigg

et al. 2006

Intl Journal of Climatology

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The interannual variability of the tropical Atlantic ocean-atmosphere system is examined using 50 years of sea-surface temperature (SST) and re-analysis data, and satellite data when available. A singular value decomposition analysis of 12-to 72-month bandpass filtered SST and zonal wind stress reveals two dominant modes of interannual variability. The SST anomalies are confined to the North Tropical Atlantic (NTA) in the first mode and extend over the equatorial and South Tropical Atlantic in the second mode. No evidence is found for an Atlantic SST dipole. The structure of the first (NTA) mode is examined in detail here, while the second mode has been described in a companion paper. In particular, the relationship of the NTA mode with El Niño-Southern Oscillation (ENSO) is investigated. There are 12 NTA events (seven warm and five cold) that are associated with ENSO, and 18 NTA events (seven warm and 11 cold) that are independent of ENSO.The ENSO-associated NTA events appear to be a passive response to remote ENSO forcing, mainly via a Pacific-North America (PNA)-like wave train that induces SST anomalies over the NTA through changes in the surface wind and latent heat flux. The NTA anomalies peak four months after ENSO. There does not appear to be an atmospheric response to the NTA SST anomalies as convection over the Atlantic is suppressed by the anomalous Walker circulation due to ENSO.The ENSO-independent NTA events also appear to be induced by an extratropical wave train from the Pacific sector (but one that is independent of Pacific SST), and forcing by the North Atlantic Oscillation (NAO) also contributes. As the event matures, the atmosphere does respond to the NTA SST anomalies, with enhanced convection over the Caribbean and a wave train that propagates northeastward to Europe.

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The Atlantic zonal mode: Dynamics, thermodynamics, and teleconnections

Richter

Tokinaga

2021

Tropical and Extratropical Air-Sea Interactions

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A Quasi‐Biennial Oscillation in the equatorial Atlantic Ocean

Cited by 7 publications

References 17 publications

Interannual variability of the Tropical Atlantic independent of and associated with ENSO: Part II. The South Tropical Atlantic

Interannual variability of the Tropical Atlantic independent of and associated with ENSO: Part II. The South Tropical Atlantic

Interannual variability of the tropical Atlantic independent of and associated with ENSO: Part I. The North Tropical Atlantic

The Atlantic zonal mode: Dynamics, thermodynamics, and teleconnections

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