Weakened Interannual Variability in the Tropical Pacific Ocean since 2000

Hu, Zeng‐Zhen; Kumar, Arun; Ren, Hong‐Li; Wang, Hui; L’Heureux, Michelle; Jin, Fei‐Fei

doi:10.1175/jcli-d-12-00265.1

Cited by 138 publications

(122 citation statements)

References 49 publications

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“…As shown in Fig. 1a ) after 2000 in the east region, which concurs with previous studies that the coupling relationship weakened in the eastern Pacific in the 2000s (Choi et al 2011;Hu et al 2013;Zheng et al 2014). Similar variations in those two areas are also observed with the Optimum Interpolation version 2 SST data (Reynolds et al 2002;Supplement 2).…”

Section: Climate Shift In the Hf-sst Coupling Processsupporting

confidence: 91%

“…As documented by Barnston et al (2012), an apparent retrogression in skill exists in ENSO predictions from 2002 to 2011, compared with the predictions from 1981 to 2010. Meanwhile, the central Pacific (CP) ENSO occurred more frequently with the locus of warming sea surface temperature (SST) anomalies shifted westward toward the dateline (McPhaden 2012;Hu et al 2013;Yu et al 2015), indicating a possible link to the changed mean state around 2000 (McPhaden et al 2011;Yu and Kim 2011;Chung and Li 2013;Han et al 2014). The changing ENSO characteristics (e.g., weaker-amplitude, high-frequency CP ENSO events) after the climate shift resulted in the degradation of ENSO performances (Barnston et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Bias Corrections of the Heat Flux Damping Process to Improve the Simulation of ENSO Post-2000

Zhao

Chen

Zheng

2015

SOLA

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Around 2000, El Niño-Southern Oscillation (ENSO) began to experience weaker-intensity, but more frequent events (i.e., the increased central-Pacific (CP) ENSO), when a climate transition characterized by a La Niña-like mean state coincidently occurred. Associated with this climate shift, the ENSO simulation and prediction skills of most models in the 2000s were significantly lower than those in the 1980−90s, which had common biases that were amplified through this climate transition. In this work, a model bias is examined with the heat flux (HF)-sea surface temperature (SST) coupling processes over the tropical Pacific, which experienced coupling strength modification around 2000 over both the regions west and east of 160°W. A simple ENSO coupled model trained with the observations before 2000 is used to demonstrate that this model bias can be alleviated by updating the HF-SST coupling parameters. After updating these parameters, the performance of the ENSO model is significantly improved for reproducing observations over the tropical Pacific after the year 2000, suggesting the potential for a substantial improvement in ENSO simulation and prediction.

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Section: Climate Shift In the Hf-sst Coupling Processsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Bias Corrections of the Heat Flux Damping Process to Improve the Simulation of ENSO Post-2000

Zhao

Chen

Zheng

2015

SOLA

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“…While the sensitivity of ENSO to different mean wind stress or Z20 has been tested using the simplified systems [e.g., Hu et al, 2013], the decadal variability of the Z20-SST relationship has never been included in such analyses. Because of the vital contribution of the thermocline feedback to the ENSO growth rate [e.g., Ren and Jin, 2013], one would expect that the decadal variability of the Z20-SST relationship would modulate the simulated ENSO properties.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

The relationship between thermocline depth and SST anomalies in the eastern equatorial Pacific: Seasonality and decadal variations

Zhu

Kumar

Huang

2015

Geophysical Research Letters

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Even though the vital role of thermocline fluctuation in El Niño–Southern Oscillation (ENSO) cycle has been established previously, the direct relationship between the thermocline depth and sea surface temperature (SST) anomalies in the equatorial Pacific is yet to be fully understood, especially its seasonality. Thermocline depth anomalies have been found to lead SST anomalies in time with a longitude‐dependent delay, but our study also suggests that the relationship shows considerable seasonal dependency and is strongest (weakest) during the boreal spring (summer). Over the eastern equatorial Pacific where there is least delay (compared to that in the western and central Pacific), the connection between thermocline and SST is the weakest during the boreal spring. This feature may be one of causes for ENSO spring persistence barrier. Furthermore, the thermocline‐SST connections exhibit significant decadal variations, which are remarkably consistent with the decadal changes in the persistence barrier of SST anomalies over the eastern Pacific. It is also found that the decadal shift in the timing of the thermocline‐SST connection barrier is caused by the changes in the seasonal cycle of tropical trade winds and thermocline depths.

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“…A recent study has reported the weakened interannual variability in the tropical Pacific Ocean since 2000 (Hu et al 2013). This is conceivable if WP ENSO events keep occurring actively but CT ENSO becomes inactive under the current climate conditions, and thus the total ENSO period might be shortening since 2000 (refer to the indices in Fig.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

ENSO Regime Change since the Late 1970s as Manifested by Two Types of ENSO

Ren

Jin

Stuecker

et al. 2013

Journal of the Meteorological Society of Japan

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During the late 1970s, the El Niño-Southern Oscillation (ENSO) experienced a notable regime change, manifested by a change in amplitude, dominant ENSO period, and sea surface temperature anomaly (SSTA) propagation characteristics. The present study shows that these features of the ENSO regime change are associated with property changes of the canonical ENSO, i.e., cold-tongue (CT) type ENSO. Another signature of the ENSO regime change is manifested in the frequent occurrence of a warm-pool (WP) type ENSO that accompanies SSTAs centered over the central Pacific near the WP edge and exhibits characteristics differing from those of the CT ENSO. The distinct manifestations of the two types of ENSO detected in this ENSO regime change are clearly identifiable with the removal of the strong background decadal signal. Since the late 1970s, the WP ENSO has featured a weak eastward (westward) propagation of the SSTA center in the developing (decaying) phase, which makes no net contribution to the observed eastward propagation, and a 2̶3 yr period compared to the 4̶5 yr period of the CT ENSO. Observations strongly suggest that the WP and CT ENSO are independent quasi-biennial and quasi-quadrennial modes, respectively, of the tropical Pacific climate variability. Our observations also suggest that these two ENSO modes have coexisted actively since the late 1970s when either El Niño or La Niña can be separated into the two types.

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Weakened Interannual Variability in the Tropical Pacific Ocean since 2000

Cited by 138 publications

References 49 publications

Bias Corrections of the Heat Flux Damping Process to Improve the Simulation of ENSO Post-2000

Bias Corrections of the Heat Flux Damping Process to Improve the Simulation of ENSO Post-2000

The relationship between thermocline depth and SST anomalies in the eastern equatorial Pacific: Seasonality and decadal variations

ENSO Regime Change since the Late 1970s as Manifested by Two Types of ENSO

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