Equatorial Origin of the Observed Tropical Pacific Quasi‐Decadal Variability From ENSO Nonlinearity

Liu, Chao; Zhang, Wenjun; Jin, Fei‐Fei; Stuecker, Malte F.; Geng, Licheng

doi:10.1029/2022gl097903

Cited by 8 publications

(8 citation statements)

References 84 publications

(121 reference statements)

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“…1b, c). Consistent with previous findings 3,16,21 , the pronounced decadal variability is found in the Niño4 region, characterized by a distinct spectral peak within 8 and 16-year periods (Fig. 1b).…”

Section: Resultssupporting

confidence: 92%

“…Since the TPDV and ENSO share a similar structure and major episodes of decadal climate variability are well captured by the relative number of El Niño and La Niña events 3 , TPDV is therefore merely regarded as the long-term linear average of the ENSO cycle 22 or the residual signal modulated by the nonlinearity of ENSO 23 . This implies that TPDV may largely originate in the tropical Pacific 16 . However, the wintertime stochastic forcings in the extratropical North and South Pacific have been put forward as the primary driver of TPDV 10,[24][25][26] .…”

mentioning

confidence: 99%

“…However, TPDV exhibits a wider meridional extent 13,14 and shows stronger variability in the tropics than in the extra-tropics 1,3,14,15 . Recent studies have also identified that TPDV manifests the largest loadings in the equatorial central and northeastern Pacific 3,15,16 , bearing resemblance to the Central Pacific El Niño 17,18 and the Pacific Meridional Mode (PMM) patterns 19,20 . In addition, some studies suggested that TPDV exhibits a prominent periodicity of around 11 years 16,21 mainly observed after 1950 21 .…”

mentioning

confidence: 99%

“…Recent studies have also identified that TPDV manifests the largest loadings in the equatorial central and northeastern Pacific 3,15,16 , bearing resemblance to the Central Pacific El Niño 17,18 and the Pacific Meridional Mode (PMM) patterns 19,20 . In addition, some studies suggested that TPDV exhibits a prominent periodicity of around 11 years 16,21 mainly observed after 1950 21 . Therefore, our focus will be specifically on the TPDV at this timescale range.…”

mentioning

confidence: 99%

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A key role of off-equatorial subsurface temperature anomalies in Tropical Pacific Decadal Variability

San,

Tseng,

Ding

et al. 2024

npj Clim Atmos Sci

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We demonstrate the key role of off-equatorial subsurface temperature anomalies in driving the phase transition of Tropical Pacific Decadal Variability (TPDV) using observation and model experiments. During the positive phase of TPDV, anomalous atmospheric responses in the off-equatorial northwestern Pacific induce positive Ekman pumping. The resulting negative subsurface temperature anomaly generated then propagates along the North Equatorial Countercurrent pathway towards the central basin, causing a sign reversal of the equatorial sea-surface temperature anomalies around three years later. Moreover, the positive phase of TPDV possibly changes the state of the Kuroshio Extension through tropical-extratropical interaction, which subsequently projects onto the footprint of the Pacific Meridional Mode, thereby amplifying subsurface-produced disturbance 0–12 months before the cold peak phase. The cold phase is completely established after five years. Similarly, the same dynamic applies to the reversed phase, leading to a preferred decadal oscillation driven by off-equatorial subsurface temperature anomalies and extratropical-tropical ocean-atmosphere interaction.

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Section: Resultssupporting

confidence: 92%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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A key role of off-equatorial subsurface temperature anomalies in Tropical Pacific Decadal Variability

San,

Tseng,

Ding

et al. 2024

npj Clim Atmos Sci

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“…Not discussed here but of equal importance are the imprints that ENSO can have (in addition to the double integration mechanism) on low-frequency variability via nonlinear rectification (Jin et al 2003;Rodgers et al 2004;Hayashi et al 2020;Park et al 2020;Liu et al 2022). Thus, both effective upscale (Stuecker et al 2015a) and downscale (Jin 2022) ENSO frequency cascades exist in the climate system.…”

Section: Discussionmentioning

confidence: 99%

The climate variability trio: stochastic fluctuations, El Niño, and the seasonal cycle

Stuecker

2023

Geosci. Lett.

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Climate variability has distinct spatial patterns with the strongest signal of sea surface temperature (SST) variance residing in the tropical Pacific. This interannual climate phenomenon, the El Niño-Southern Oscillation (ENSO), impacts weather patterns across the globe via atmospheric teleconnections. Pronounced SST variability, albeit of smaller amplitude, also exists in the other tropical basins as well as in the extratropical regions. To improve our physical understanding of internal climate variability across the global oceans, we here make the case for a conceptual model hierarchy that captures the essence of observed SST variability from subseasonal to decadal timescales. The building blocks consist of the classic stochastic climate model formulated by Klaus Hasselmann, a deterministic low-order model for ENSO variability, and the effect of the seasonal cycle on both of these models. This model hierarchy allows us to trace the impacts of seasonal processes on the statistics of observed and simulated climate variability. One of the important outcomes of ENSO’s interaction with the seasonal cycle is the generation of a frequency cascade leading to deterministic climate variability on a wide range of timescales, including the near-annual ENSO Combination Mode. Using the aforementioned building blocks, we arrive at a succinct conceptual model that delineates ENSO’s ubiquitous climate impacts and allows us to revisit ENSO’s observed statistical relationships with other coherent spatio-temporal patterns of climate variability—so called empirical modes of variability. We demonstrate the importance of correctly accounting for different seasonal phasing in the linear growth/damping rates of different climate phenomena, as well as the seasonal phasing of ENSO teleconnections and of atmospheric noise forcings. We discuss how previously some of ENSO’s relationships with other modes of variability have been misinterpreted due to non-intuitive seasonal cycle effects on both power spectra and lead/lag correlations. Furthermore, it is evident that ENSO’s impacts on climate variability outside the tropical Pacific are oftentimes larger than previously recognized and that accurately accounting for them has important implications. For instance, it has been shown that improved seasonal prediction skill can be achieved in the Indian Ocean by fully accounting for ENSO’s seasonally modulated and temporally integrated remote impacts. These results move us to refocus our attention to the tropical Pacific for understanding global patterns of climate variability and their predictability.

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A spatiotemporal oscillator model for ENSO

2024

Theor Appl Climatol

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A spatiotemporal oscillator model for El Niño/Southern Oscillation (ENSO) is constructed based on the thermodynamics and thermocline dynamics. The model is enclosed by introducing a proportional relationship between the gradient in sea surface temperature (SST) and the oceanic zonal current and can be transformed into a standard wave equation that can be decomposed into a series of eigenmodes by cosine series expansion. Each eigenmode shows a spatial mode that oscillates with its natural frequency. The first spatial mode, that highlights SST anomaly (SSTA) contrast between the eastern and western Pacific—a fundamental characteristic of the eastern Pacific (EP) El Niño events, oscillates with a natural period of around 4.6 years, consistent with the quasi-quadrennial (QQ) mode. The second spatial mode, that emphasizes SSTA contrast between the central and the eastern, western Pacific—a basic spatial structure of the central Pacific (CP) El Niño events, oscillates with a natural period of 2.3 years that is half of the first natural period. It is also consistent with the quasi-biennial (QB) modes. The combinations of the eigenmodes with different weights can feature complex spatiotemporal variations in SSTAs. In open ocean that is far away from the coastlines, the model can predict waves propagating both eastward and westward. Besides, the net surface heating further complicates the temporal variations by exerting forced frequencies. The model unifies the temporal and spatial variations and may provide a comprehensive viewpoint for understanding the complex spatiotemporal variations of ENSO.

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Equatorial Origin of the Observed Tropical Pacific Quasi‐Decadal Variability From ENSO Nonlinearity

Cited by 8 publications

References 84 publications

A key role of off-equatorial subsurface temperature anomalies in Tropical Pacific Decadal Variability

A key role of off-equatorial subsurface temperature anomalies in Tropical Pacific Decadal Variability

The climate variability trio: stochastic fluctuations, El Niño, and the seasonal cycle

A spatiotemporal oscillator model for ENSO

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