The role of the southward wind shift in both, the seasonal synchronization and duration of ENSO events

Abellán, Esteban; McGregor, Shayne

doi:10.1007/s00382-015-2853-1

Cited by 23 publications

(13 citation statements)

References 100 publications

(136 reference statements)

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“…In our study it was also noted that the magnitude of the event, in terms of SST anomalies, is larger and the termination is more rapid in models with an SWS compared to models without an SWS for La Niña and strong El Niño, more evident for the latter. These findings are consistent with those reported by Abellán and McGregor (2016), where they pointed out that the inclusion of the SWS in their simple model results in larger La Niña events and shorter El Niño events. In association, models that successfully reproduce the SWS, peaks of La Niña, and strong El Niño match observations much better than models that do not accurately produce the SWS.…”

Section: Discussionsupporting

confidence: 93%

“…As to whether the improvements in SWS representation in the CMIP5 models with SWS is due to the more realistic synchronization of ENSO events, we revert to past literature that shows that SWS can be generated for arbitrary frequencies of ENSO anomalies (Spencer 2004;Stuecker et al 2015). Further to this, the study of Abellán and McGregor (2016) suggests that the SWS plays a crucial role in the synchronization of ENSO events to the seasonal cycle.…”

Section: Seasonal Synchronization and Swsmentioning

confidence: 89%

“…However, the exact mechanisms are not yet fully understood, with several potential mechanisms proposed linking ENSO and the annual cycle (e.g., Philander 1983;Philander et al 1984;Zebiak and Cane 1987;Cane et al 1990;Jin et al 2003;Dommenget and Yu 2016). Despite this ongoing scientific debate, the southward wind shift (SWS) has been increasingly recognized as one of the major negative feedbacks involved in ENSO seasonal phase locking and termination (Harrison and Vecchi 1999;Vecchi and Harrison 2003;Lengaigne et al 2006;Lengaigne and Vecchi 2009;McGregor et al 2012aMcGregor et al , 2014Stuecker et al 2013;Abellán and McGregor 2016); the climate dynamics linking the SWS to seasonal phase locking will be described below.…”

Section: Introductionmentioning

confidence: 99%

“…In terms of its consequences, the SWS has been shown to 1) make the thermocline depth in the eastern equatorial Pacific return to normal values (e.g., Harrison and Vecchi 1999;Harrison 2003, 2006;Lengaigne et al 2006), 2) play a crucial role in the discharge process of the warm water volume (WWV) during El Niño events (McGregor et al 2012a, and 3) transfer mass between the Northern and Southern Hemisphere during El Niño events (McGregor et al 2014). Recently, Abellán and McGregor (2016) utilized a simple coupled model to demonstrate that the SWS during El Niño events plays a crucial role in the synchronization of the events with the annual cycle as well as a rapid termination of these events.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the Southward Wind Shift of ENSO in CMIP5 Models

2017

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During the mature phase of El Niño–Southern Oscillation (ENSO) events there is a southward shift of anomalous zonal winds (SWS), which has been suggested to play a role in the seasonal phase locking of ENSO. Motivated by the fact that coupled climate models tend to underestimate this feature, this study examines the representation of the SWS in phase 5 of the Coupled Model Intercomparison Project (CMIP5). It is found that most models successfully reproduce the observed SWS, although the magnitude of the zonal wind stress anomaly is underestimated. Several significant differences between the models with and without the SWS are identified including biases in the magnitude and spatial distribution of precipitation and sea surface temperature (SST) anomalies during ENSO. Multiple-linear regression analysis suggests that the climatological meridional SST gradient as well as anomalous ENSO-driven convective activity over the northwest Pacific both might play a role in controlling the SWS. While the models that capture the SWS also simulate many more strong El Niño and La Niña events peaking at the correct time of year, the overall seasonal synchronization is still underestimated in these models. This is attributed to underestimated changes in warm water volume (WWV) during moderate El Niño events so that these events display relatively poor seasonal synchronization. Thus, while the SWS is an important metric, it is ultimately the magnitude and zonal extent of the wind changes that accompany this SWS that drive the changes in WWV and prime the system for termination.

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Section: Discussionsupporting

confidence: 93%

Section: Seasonal Synchronization and Swsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of the Southward Wind Shift of ENSO in CMIP5 Models

2017

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“…However, our results clearly show that multi-year La Niña is not a statistical artefact but a part of the intrinsic complex nature of ENSO. Previous studies have shown the contribution of anomalous wind stress curl causing GHT in the ENSO transition 9,20,31−33 , an active role of inter-basin interaction for the transition asymmetry 34 , and a meridional shift of westerly surface wind anomalies for the transition from extreme El Niño to La Niña [12][13][14]35 . Although we do not exclude these processes during ENSO phase transition, we demonstrate that the anomalous Ekman heat transport is crucial to transition from extreme El Niño to multi-year La Niña.…”

Section: Analysis Of Cmip6 Control Simulationsmentioning

confidence: 99%

Mechanisms linking multi-year La Niña with preceding extreme El Niño

Iwakiri

2020

Preprint

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El Niño/La Niña, characterized by anomalous sea surface temperature warming/cooling in the central-eastern equatorial Pacific, is a dominant interannual variability with irregularity, impacting worldwide weather and socioeconomics. The observed records show that La Niña often persists for more than two years, called “multi-year La Niña” which tends to accompany extreme El Niño in the preceding year; however, the physical linkage between them remains unclear. Here we show using reanalysis data that an extreme El Niño excites atmospheric conditions that favor the generation of the multi-year La Niña in subsequent years. Easterly wind anomalies along the northern off-equator in the Pacific during the decay phase of an extreme El Niño are crucial. They act to discharge ocean heat content (OHC) via an anomalous northward Ekman transport; the negative OHC anomaly is large enough to be restored by a single La Niña and, therefore, causes another La Niña to occur in the second year. Furthermore, analyses of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models show that the occurrence frequencies of multi-year La Niña and extreme El Niño are highly correlated, supporting the abovementioned mechanism. Our results provide physical evidence that the increasing frequency of multi-year La Niña is explained by the increasing El Niño amplitude since the late 20th century.

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