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

Handoh, Itsuki C.; Matthews, Adrian J.; Bigg, Grant R.; Stevens, David P.

doi:10.1002/joc.1343

Cited by 58 publications

(49 citation statements)

References 57 publications

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“…The mechanisms responsible for the link between ENSO and the NTA variability have been extensively studied (e.g., Nobre and Shukla 1996;Saravanan and Chang 2000;Sutton et al 2000;Wang 2002Wang , 2004Handoh et al 2006). There are at least two mechanisms via which ENSO may influence the NTA region: 1) changes to the tropical Walker and Hadley circulations and associated patterns of deep convection (Bjerknes 1969;Oort and Rasmusson 1970) and 2) tropical-extratropical interaction via the Pacific-North American (PNA) teleconnection pattern (Wallace and Gutzler 1981).…”

Section: Introductionmentioning

confidence: 99%

“…Some controversy remains regarding which of the above mechanisms plays a major role in the link between ENSO and NTA variability . Handoh et al (2006) emphasized the important role of tropical-extratropical interaction in inducing anomalous SST over the NTA. Their analysis suggests that the ENSO-associated NTA SSTA is forced by an extratropical PNA-like wave train emanating from the Pacific, rather than by a change in the Walker circulation.…”

Section: Introductionmentioning

confidence: 99%

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Winter Persistence Barrier of Sea Surface Temperature in the Northern Tropical Atlantic Associated with ENSO

Ding

2011

Journal of Climate

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This study investigates the persistence characteristics of the sea surface temperature anomaly (SSTA) in the northern tropical Atlantic (NTA). It is found that a persistence barrier exists around December and January. This winter persistence barrier (WPB) is prominent during the mature phase of strong ENSO events but becomes indistinct during weak ENSO and normal (non-ENSO) events. During strong El Niñ o events, the NTA SSTA shows a reversal in sign and a rapid warming during December and January. It is possible that this SSTA sign reversal reduces the persistence, leading to the occurrence of the NTA WPB. The present analyses indicate a dynamic relationship among the Pacific ENSO, the NTA SSTA, and the NTA WPB on a quasibiennial time scale: a strong El Niñ o event is usually preceded by a strong La Niñ a event, which leads to a sign reversal of the NTA SSTA in winter as a delayed response to ENSO, finally resulting in the NTA WPB. Analyses also suggest that the NTA WPB is affected by the North Atlantic Oscillation (NAO). The NAO enhances the persistence of the NTA SSTA during winter, tending to weaken the NTA WPB.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Winter Persistence Barrier of Sea Surface Temperature in the Northern Tropical Atlantic Associated with ENSO

Ding

2011

Journal of Climate

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“…One of the most robust ENSO teleconnections is the link between SST anomalies in the equatorial Pacific and those in the tropical North Atlantic (TNA): a broad region of positive (negative) SST anomalies to the north of the equatorial Atlantic lags the mature phase of El Niño (La Niña) in boreal winter [December-February (DJF)], peaking in boreal spring [March-May (MAM)] (e.g., Lee et al 2008). This one-season-lagged ENSO-TNA teleconnection is linear with respect to the phase of ENSO (e.g., Czaja et al 2002;Handoh et al 2006).…”

Section: Introductionmentioning

confidence: 99%

“…1, left). Both teleconnection mechanisms act upon the strength of the Azores anticyclone (and related trade winds), which represents an atmospheric forcing of the subtropical circulation that does not appear to trigger the WES feedback (Handoh et al 2006), since the latter is mainly confined to the deep tropics (08-108/158N; Czaja et al 2002). Modeling ) and observational (Chiang et al 2002) studies have found that positive feedback between cross-equatorial winds and SST gradient takes place only in the deep TNA.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the ENSO Teleconnection to the Tropical North Atlantic

et al. 2017

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One of the most robust remote impacts of El Niño-Southern Oscillation (ENSO) is the teleconnection to tropical North Atlantic (TNA) sea surface temperature (SST) in boreal spring. However, important questions still remain open. In particular, the timing of the ENSO-TNA relationship lacks understanding. The three previously proposed mechanisms rely on teleconnection dynamics involving a time lag of one season with respect to the ENSO mature phase in winter, but recent results have shown that the persistence of ENSO into spring is necessary for the development of the TNA SST anomalies. Likewise, the identification of the effective atmospheric forcing in the deep TNA to drive the regional air-sea interaction is also lacking. In this manuscript a new dynamical framework to understand the ENSO-TNA teleconnection is proposed, in which a continuous atmospheric forcing is present throughout the ENSO decaying phase. Observational datasets in the satellite era, which include reliable estimates over the ocean, are used to illustrate the mechanism at play. The dynamics rely on the remote Gill-type response to the ENSO zonally compensated heat source over the Amazon basin, associated with perturbations in the Walker circulation. For El Niño conditions, the anomalous diabatic heating in the tropical Pacific is compensated by anomalous diabatic cooling, in association with negative rainfall anomalies and descending motion over northern South America. A pair of anomalous cyclonic circulations is established at upper-tropospheric levels in the tropical Atlantic straddling the equator, displaying a characteristic baroclinic structure with height. In the TNA region, the mirrored anomalous anticyclonic circulation at lower-tropospheric levels weakens the northeasterly trade winds, leading to a reduction in evaporation and of the ocean mixed layer depth, hence to positive SST anomalies. Apart from the dominance of latent heat flux anomalies in the remote response, sensible heat flux and shortwave radiation anomalies also appear to contribute. The ''lagged'' relationship between mature ENSO in winter and peaking TNA SSTs in spring seems to be phase locked with the seasonal cycle in both the location of the mechanism's centers of action and regional SST variance.

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“…Following the ENSO-related SST signal peaked in the northern winter in the eastern Pacific, the SST anomalies in the Indian-Western Pacific (Hsiung and Newell 1983;Pan and Oort 1983;Lanzante 1996;Lau et al 2005 and references there in) as well as that in the tropical Atlantic (Enfield and Mayer 1997;Huang et al 2002;Ding and Li 2011 and references there in) attain their maximum amplitude 1-2 seasons later. They are remotely forced by ENSO through a series of atmospheric and ocean processes involving the ''atmospheric bridge'' spanning the Pacific and Indian Ocean (Lau and Nath 2003;Klein et al 1999), the anomalous Walker circulation (Saravanan and Chang 2000) and the PNA-like teleconnection pattern (Handoh et al 2006) spanning the Pacific and the tropical Atlantic. The delayed change of SST in the Indian and the Atlantic sectors also results in an increase in zonal homogeneity of the tropical SST anomalies and the related tropical atmospheric response (Kumar and Hoerling 2003).…”

Section: Introductionmentioning

confidence: 99%

Observational evidence of the delayed response of stratospheric polar vortex variability to ENSO SST anomalies

et al. 2011

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The temporal and spatial relationship between ENSO and the extratropical stratospheric variability in the Northern Hemisphere is examined. In general, there exists a negative correlation between ENSO and the strength of the polar vortex, but the maximum correlation is found in the next winter season after the mature phase of ENSO event, rather than in the concurrent winter. Specifically, the stratospheric polar vortex tends to be anomalously warmer and weaker in both the concurrent and the next winter season following a warm ENSO event, and vice versa. However, the polar anomalies in the next winter are much stronger and with a deeper vertical structure than that in the concurrent winter. Our analysis also shows that, the delayed stratospheric response to ENSO is characterized with poleward and downward propagation of temperature anomalies, suggesting an ENSO-induced interannual variability of the global mass circulation in the stratosphere. Particularly, in response to the growing of a warm ENSO event, there exist warm temperature and positive isentropic mass anomalies in the midlatitude stratosphere since the preceding summer. The presence of an anomalous wavenumber-1 in the concurrent winter, associated with an anomalous Aleutian high, results in a poleward extension of warm anomalies into the polar region, and thus a weaker stratospheric polar vortex. However, the midlatitude warm temperature and positive isentropic mass anomalies persist throughout the concurrent winter till the end of the next summer. In comparison with the concurrent winter, the strengthening of poleward heat transport by an anomalous wavenumber-2 in the next winter results in a much warmer and weaker polar vortex accompanied with a colder midlatitude stratosphere.

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

Cited by 58 publications

References 57 publications

Winter Persistence Barrier of Sea Surface Temperature in the Northern Tropical Atlantic Associated with ENSO

Winter Persistence Barrier of Sea Surface Temperature in the Northern Tropical Atlantic Associated with ENSO

Revisiting the ENSO Teleconnection to the Tropical North Atlantic

Observational evidence of the delayed response of stratospheric polar vortex variability to ENSO SST anomalies

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