Western Pacific Oceanic Heat Content: A Better Predictor of La Niña Than of El Niño

Planton, Yann; Vialard, Jérôme; Guilyardi, Éric; Lengaigne, Matthieu; Izumo, Takeshi

doi:10.1029/2018gl079341

Cited by 38 publications

(42 citation statements)

References 88 publications

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“…The strong dependence of SST variations on thermocline depth in the eastern equatorial Pacific thus prohibits the genesis of warm-pool El Niño events, which peak near the equatorial date line (Kug et al 2009). In addition, a series of recent observational analyses show that upper-ocean heat content prior to boreal summer appears to be a better precursor for La Niña than for El Niño (Neske and McGregor 2018;Planton et al 2018), with the latter being more relevant to westerly wind bursts in the boreal spring and summer seasons (Santoso et al 2017). The strong dependence of modeled El Niño and La Niña on the upper-ocean heat content thus reduces the asymmetry in modeled ENSO.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Effects of Tropical Cyclones on ENSO

et al. 2019

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Numerous studies have investigated the role of El Niño–Southern Oscillation (ENSO) in modulating the activity of tropical cyclones (TCs) in the western Pacific on interannual time scales, but the effects of TCs on ENSO are less discussed. Some studies have found that TCs sharply increase surface westerly anomalies over the equatorial western–central Pacific and maintain them there for a few days. Given the strong influence of equatorial surface westerly wind bursts on ENSO, as confirmed by much recent literature, the effects of TCs on ENSO may be much greater than previously expected. Using recently released observations and reanalysis datasets, it is found that the majority of near-equatorial TCs (simply TCs hereafter) are associated with strong westerly anomalies at the equator, and the number and longitude of TCs are significantly correlated with ENSO strength. When TC-related wind stresses are added into an intermediate coupled model, the simulated ENSO becomes more irregular, and both ENSO magnitude and skewness approach those of observations, as compared with simulations without TCs. Adding TCs into the model system does not break the linkage between the heat content anomaly and subsequent ENSO event in the model, which manifest the classic recharge–discharge ENSO dynamics. However, the influence of TCs on ENSO is so strong that ENSO magnitude and sometimes its final state—that is, either El Niño or La Niña—largely depend on the number and timing of TCs during the event year. Our findings suggest that TCs play a prominent role in ENSO dynamics, and their effects must be considered in ENSO forecast models.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Effects of Tropical Cyclones on ENSO

et al. 2019

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“…In fact, the western and eastern parts of WWV may have different features. For example, a recent study of Planton et al (2018) argued that compared with the eastern part of the WWV, the western part of the WWV has a longer lead time and higher correlation with ENSO than the full WWV, and hence is a better predictor. The reduction of OTA variability was also confirmed by the analysis of the mixed layer ocean heat budget along the equatorial Pacific (not shown).…”

Section: A Enso Variability Changementioning

confidence: 99%

“…The maximum correlation coefficients also decreased in the latter period, which is consistent with the results of McPhaden (2012), Horii et al (2012), and Kumar and Hu (2014a). The decline in the lead time, together with the suppression of ENSO variability, reduces the usefulness of WWV as a predictor for ENSO after 2000, although the recharge-discharge processes still controlled ENSO evolution to some extent Gorder 2001, 2003;Chen et al 2004;Kug et al 2005;Clarke et al 2007;Wen et al 2014;Neske and McGregor 2018;Planton et al 2018;Clarke and Zhang 2019). Bunge and Clarke (2014) point out that the decreased lead time is related to an increase of the variance in the tilt (east-west dipole) mode of thermocline variations and a decrease in the amplitude of the WWV mode.…”

Section: Consequences and Impacts On Seasonal Climate Predictionmentioning

confidence: 99%

The Interdecadal Shift of ENSO Properties in 1999/2000: A Review

Kumar

Huang

et al. 2020

Journal of Climate

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Following the interdecadal shift of El Niño–Southern Oscillation (ENSO) properties that occurred in 1976/77, another regime shift happened in 1999/2000 that featured a decrease of variability and an increase in ENSO frequency. Specifically, the frequency spectrum of Niño-3.4 sea surface temperature shifted from dominant variations at quasi-quadrennial (~4 yr) periods during 1979–99 to weaker fluctuations at quasi-biennial (~2 yr) periods during 2000–18. Also, the spectrum of warm water volume (WWV) index had almost no peak in 2000–18, implying a nearly white noise process. The regime shift was associated with an enhanced zonal gradient of the mean state, a westward shift in the atmosphere–ocean coupling in the tropical Pacific, and an increase in the static stability of the troposphere. This shift had several important implications. The whitening of the subsurface ocean temperature led to a breakdown of the relationship between WWV and ENSO, reducing the efficacy of WWV as a key predictor for ENSO and thus leading to a decrease in ENSO prediction skill. Another consequence of the higher ENSO frequency after 1999/2000 was that the forecasted peak of sea surface temperature anomaly often lagged that observed by several months, and the lag increased with the lead time. The ENSO regime shift may have altered ENSO influences on extratropical climate. Thus, the regime shift of ENSO in 1999/2000 as well as the model default may account for the higher false alarm and lower skill in predicting ENSO since 1999/2000.

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“…Several studies have attempted to separate the WWV anomaly into its slower RW and faster KW components using various methods (Meinen and McPhaden 2000;Neske and McGregor 2018;Planton et al 2018;Izumo et al 2019). This partitioning allows more insight into ENSO dynamics that is not possible when considering the WWV anomaly as a whole.…”

Section: Introductionmentioning

confidence: 99%

Wind Spatial Structure Triggers ENSO’s Oceanic Warm Water Volume Changes

et al. 2021

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This study demonstrates that the generalization that strong anomalous equatorial Pacific westerly (easterly) winds during El Niño (La Niña) events displays strong adjusted warm water volume (WWV) discharges (recharges) is often incorrect. Using ocean model simulations, we categorize the oceanic adjusted responses to strong anomalous equatorial winds into two categories: (i) transitioning (consistent with the above generalization); and (ii) neutral adjusted responses (with negligible WWV re- and discharge) During the 1980-2016 period only 47% of strong anomalous equatorial winds are followed by transitioning adjusted responses, while the remaining are followed by neutral adjusted responses. Moreover, 55% (only 30%) of the strongest winds lead to transitioning adjusted responses during the pre-2000 (post-2000) period in agreement with the previously reported post-2000 decline of WWV lead time to El Niño-Southern Oscillation (ENSO) events. The prominent neutral adjusted WWV response is shown to be largely excited by anomalous wind stress forcing with a weaker curl (on average consistent with a higher ratio of off-equatorial to equatorial wind events) and weaker Rossby wave projection than the transitioning adjusted response. We also identify a prominent ENSO phase asymmetry where strong anomalous equatorial westerly winds (i.e., El Niño events) are roughly 1.6 times more likely to strongly discharge WWV than strong anomalous equatorial easterly winds (i.e., La Niña events) are to strongly recharge WWV. This ENSO phase asymmetry may be added to the list of mechanisms proposed to explain why El Niño events have a stronger tendency to be followed by La Niña events than vice versa.

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Western Pacific Oceanic Heat Content: A Better Predictor of La Niña Than of El Niño

Cited by 38 publications

References 88 publications

Effects of Tropical Cyclones on ENSO

Effects of Tropical Cyclones on ENSO

The Interdecadal Shift of ENSO Properties in 1999/2000: A Review

Wind Spatial Structure Triggers ENSO’s Oceanic Warm Water Volume Changes

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