Influence of the Pacific Meridional Mode on ENSO Evolution and Predictability: Asymmetric Modulation and Ocean Preconditioning

Fan, Hanjie; Huang, Bohua; Yang, Song; Dong, Wenjie

doi:10.1175/jcli-d-20-0109.1

Cited by 26 publications

(27 citation statements)

References 40 publications

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“…This finding indicates that the tropical Pacific Ocean is always crucial to the formation of both types of El Niño events, while the subtropical and extratropical Pacific can help adjust the zonal maximum SST center and the amplitude of the El Niño events during their developing stages. This is in agreement with Fan et al (2020), who indicated that the NPMM can be a trigger, instead of a generator for ENSO.…”

Section: Conclusion and Discussionsupporting

confidence: 92%

Toward an Optimal Observational Array for Improving Two Flavors of El Niño Predictions in the Whole Pacific

Hou

Tang

Duan

et al. 2022

Preprint

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This paper investigates the optimal observational array for improving the prediction of the El Niño-Southern Oscillation (ENSO) by exploring sensitive areas for target observations of two types of El Niño events in the whole Pacific. A target observation method based on the particle filter and pre-industrial control runs from six coupled model outputs in Coupled Model Intercomparison Project Phase 5 (CMIP5) experiments are used to quantify the relative importance of the initial accuracy of sea surface temperature (SST) in different Pacific areas. The initial accuracy of the tropical Pacific, subtropical Pacific, and extratropical Pacific can all exert influences on both types of El Niño predictions. The relative importance of different areas changes along with different lead times of predictions. Tropical Pacific observations are crucial in decreasing the root mean square error of predictions of all lead times. Subtropical and extratropical observations play an important role in decreasing the prediction uncertainty, especially when the prediction is made before and throughout boreal spring. To consider different El Niño types and different start months for predictions, a quantitative frequency method based on frequency distribution is applied to determine the optimal observations of ENSO predictions. The final optimal observational array contains 31 grid points, including 21 grid points in the equatorial Pacific and 10 grid points in the north Pacific, suggesting the importance of the initial SST conditions for ENSO predictions not only in the tropical Pacific but also in the area outside the tropics. Furthermore, the predictions made by assimilating SST in sensitive areas have better prediction skills in the verification experiment, which can indicate the validity of the optimal observational array designed in this study.

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Section: Conclusion and Discussionsupporting

confidence: 92%

Toward an Optimal Observational Array for Improving Two Flavors of El Niño Predictions in the Whole Pacific

Hou

Tang

Duan

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…The reason why SST and HC are used as inputs is that it is well known that ocean HC resides a memory for the future ENSO evolution. In addition, the SST pattern is important because it modulates equatorial wind variability, which is a key to the ENSO evolution 7 , 35 , 36 .…”

Section: Methodsmentioning

confidence: 99%

Spatiotemporal neural network with attention mechanism for El Niño forecasts

Kim

Kwon

Kim

et al. 2022

Sci Rep

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To learn spatiotemporal representations and anomaly predictions from geophysical data, we propose STANet, a spatiotemporal neural network with a trainable attention mechanism, and apply it to El Niño predictions for long-lead forecasts. The STANet makes two critical architectural improvements: it learns spatial features globally by expanding the network’s receptive field and encodes long-term sequential features with visual attention using a stateful long-short term memory network. The STANet conducts multitask learning of Nino3.4 index prediction and calendar month classification for predicted indices. In a comparison of the proposed STANet performance with the state-of-the-art model, the accuracy of the 12-month forecast lead correlation coefficient was improved by 5.8% and 13% for Nino3.4 index prediction and corresponding temporal classification, respectively. Furthermore, the spatially attentive regions for the strong El Niño events displayed spatial relationships consistent with the revealed precursor for El Niño occurrence, indicating that the proposed STANet provides good understanding of the spatiotemporal behavior of global sea surface temperature and oceanic heat content for El Niño evolution.

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“…Warm SSTAs in the southern pole extend toward the eastern North Pacific, bearing some resemblance to the Pacific Meridional Mode (Fig. 2a; Chiang and Vimont 2004;Fan et al 2021). The net surface heat flux pattern, which is dominated by latent heat flux, bears a close resemblance to the WNP SSTA pattern, indicating that net surface heat flux dominates the formation of the SSTA pattern during March-April (Figs.…”

Section: Atmospheric Circulation Associated With March Nao From Sprin...mentioning

confidence: 88%

Impact of March North Atlantic Oscillation on Indian Ocean Dipole: role of air–sea interaction over the Western North Pacific

Jiang

Liu

2022

Clim Dyn

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We investigated the relationship between the North Atlantic Oscillation (NAO) and Indian Ocean Dipole (IOD), which has remained unknown to date. Reanalysis data and linear baroclinic model experiments were employed in our study. The results showed significant correlation between the March NAO and the boreal summer and autumn IOD, independent of the El Niño–Southern Oscillation signal, verified by partial correlation analysis. Air–sea interaction over the western North Pacific (WNP) is a significant aspect of the physical mechanism through which the March NAO affects the subsequent IOD. A strong positive March NAO induces equivalent barotropic cyclonic circulation over the WNP through a steady Rossby wave, accompanied by a local tripole sea surface temperature (SST) anomaly pattern. Facilitated by local air–sea positive feedback, the low-level cyclonic circulation and associated precipitation anomalies over the WNP persist from early spring to summer and shift equatorward. During May–June, the WNP anomalous cyclone strengthens the southeasterly wind and enhances cooling off Sumatra–Java through local meridional circulation. Such circulation ascends over the WNP and descends over the tropical southeastern Indian Ocean and Maritime Continent. Subsequently, wind–evaporation–SST and wind–thermocline–SST positive feedback in the tropical Indian Ocean contribute to IOD development. A diagnosis of ocean mixed-layer heat budget indicated that the ocean dynamic process associated with the NAO contributes more to IOD development than does atmospheric thermal forcing. Determining the influence mechanism of the March NAO on the subsequent IOD is considered useful in advancing the seasonal prediction of IOD.

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Influence of the Pacific Meridional Mode on ENSO Evolution and Predictability: Asymmetric Modulation and Ocean Preconditioning

Cited by 26 publications

References 40 publications

Toward an Optimal Observational Array for Improving Two Flavors of El Niño Predictions in the Whole Pacific

Toward an Optimal Observational Array for Improving Two Flavors of El Niño Predictions in the Whole Pacific

Spatiotemporal neural network with attention mechanism for El Niño forecasts

Impact of March North Atlantic Oscillation on Indian Ocean Dipole: role of air–sea interaction over the Western North Pacific

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