A New Method for Interpreting Nonstationary Running Correlations and Its Application to the ENSO‐EAWM Relationship

Geng, Xin; Zhang, Wenjun; Jin, Fei‐Fei; Stuecker, Malte F.

doi:10.1002/2017gl076564

Cited by 17 publications

(8 citation statements)

References 28 publications

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“…The AMO modulates the ENSO–EAESM relationship not only through local air–sea forcing in the western tropical Pacific, but also through modulating mid‐to‐high latitude wave activities, leading to atmospheric circulation anomalies over East Asia and affecting the ENSO–EAESM relationship (Li et al ., 2008; Luo et al ., 2011; Zhu et al ., 2011; Geng et al ., 2017; 2018; Fan et al ., 2018). Geng et al .…”

Section: Observational Resultsmentioning

confidence: 99%

Impact of Atlantic multidecadal oscillation on interannual relationship between ENSO and East Asian early summer monsoon

et al. 2021

Intl Journal of Climatology

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Impact of the Atlantic multidecadal oscillation (AMO) on the interannual relationship between the El Niño‐Southern Oscillation (ENSO) and East Asian early summer monsoon (EAESM) is investigated using observations and community atmosphere model (CAM) outputs. We find that the interannual ENSO–EAESM relationship displays a prominent decadal variation during 1951–2018, which is consistent with the AMO phase change, that is, a high ENSO–EAESM correlation appears during the negative AMO phase, while no significant correlation is found during the positive AMO phase. Further analyses reveal that the AMO‐related sea surface temperature anomalies (SSTAs) in the western North Pacific, rather than in the North Atlantic, modulate the interannual relationship between the El Niño and EAESM. These SSTAs can prolong the existence of the anomalous western North Pacific anticyclone (WNPAC) from the ENSO mature winter to the subsequent early summer, thus affecting the ENSO–EAESM relationship for the El Niño events. In contrast, the AMO modulates the interannual relationship between the La Niña and EAESM through the North Atlantic and North Pacific. The North Atlantic warming‐induced anomalous anticyclone weakens the background cyclone over the western North Pacific during the positive AMO phase, and the mid‐latitude air–sea interaction in the North Pacific also influence the anomalous cyclone. The observed AMO's impact on the interannual relationship between the ENSO and EAESM is confirmed by atmosphere general circulation model simulations using the CAM.

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Section: Observational Resultsmentioning

confidence: 99%

Impact of Atlantic multidecadal oscillation on interannual relationship between ENSO and East Asian early summer monsoon

et al. 2021

Intl Journal of Climatology

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“…Apart from the commonly used methods such as empirical orthogonal function (EOF) analysis, (running) correlation analyses, multiple linear regression analyses and composite analyses, we also adopt a newly-proposed statistical method for interpreting nonstationary running correlations to quantitatively identify the physical reasons determining the waxing and waning of the ENSO-SCWP relationship. For more details about this method, refer to Geng et al (2018).…”

Section: Methodsmentioning

confidence: 99%

“…Next, the method for decomposing and interpreting nonstationary running correlations introduced by Geng et al . (2018) is applied to quantificationally test the hypothesis that the AMO modulates the ENSO–SCWP relationship. According to the Equation () in Geng et al .…”

Section: Nonstationary Enso–scwp Relationship Modulated By the Amomentioning

confidence: 99%

“…According to the Equation () in Geng et al . (2018), the running correlation coefficient

\overset{r}{true}

between two normalized timeseries, denoted by S for the SCWP index and by N for the Niño3.4 index, can be approximated based on a first‐order Taylor expansion as

\overset{r}{true} \approx \overset{r}{true} \underset{1 normala}{\underset{⏟}{+ ∆ \overset{true~}{italicSN}}} \underset{1 normalb}{\underset{⏟}{- \overset{true¯}{r} \frac{∆ \overset{true~}{S^{2}}}{2}}} \underset{1 normalc}{\underset{⏟}{- \overset{true¯}{r} \frac{∆ \overset{true~}{N^{2}}}{2}}},

where a tilde refers to the running correlation, running covariance, or running variance of the two time series, while an overbar denotes those same variables over the entire record duration (1951–2019). A delta (Δ) represents the difference between the covariance (or variance) over each running window and that during the entire period.…”

Section: Nonstationary Enso–scwp Relationship Modulated By the Amomentioning

confidence: 99%

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Interpreting the nonstationary relationship between El Niño–Southern Oscillation and the winter precipitation over southeast China

Tang

Geng

Zhao

et al. 2022

Intl Journal of Climatology

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The amount of winter precipitation over southeast China (SCWP) is significantly affected by the El Niño-Southern Oscillation (ENSO), with generally an enhanced SCWP response to El Niño events. In this paper, we find that this relationship shows remarkable nonstationarities on the multidecadal timescale. Running ENSO-SCWP correlation maintains statistically significant before the mid-1960s and after the mid-1990s but not during the interim period, which exhibits an approximate synchronized temporal evolution with the Atlantic Multidecadal Oscillation (AMO). A statistical method for interpreting nonstationary relationships is then applied to quantitatively verify and measure this possible AMO modulation. It is demonstrated that the nonstationary ENSO-SCWP correlation can be expressed to a large extent by the influence of the AMO-ENSO nonlinear effect (AMO*Niño3.4) on the SCWP. This influence intensifies the ENSO-SCWP relationship during the positive AMO phase but weakens it during the negative AMO phase. Therefore, the nonstationarity in the ENSO-SCWP relationship comes predominantly from an AMO modulation via this key nonlinear effect. We further suggest that a positive AMO favours a westward shift of ENSO sea surface temperature (SST) anomaly pattern in the tropical Pacific. Correspondingly, the anomalous western North Pacific (WNP) anticyclone also migrates westward, which gives rise to pronounced moisture transports and vertical motions over the adjacent southeast China, thereby resulting in a significant ENSO-SCWP relationship. In contrast, during the negative AMO phase, the eastward-shifted ENSO SST and WNP anticyclonic anomalies produce significant atmospheric anomalies primarily to the east of the Chinese mainland, thus having less effect on the SCWP.

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“…To explore which external forcing might be responsible for these decadal variations, we show in Fig. 4 also the 9-yr running averaged AMO index (blue bars), given that the AMO has been widely proposed as an important external forcing responsible for ENSO property changes and variations of ENSO-related anomalous atmospheric responses on decadal time scales (Dong et al 2006;Yu et al 2015;Levine et al 2017;Geng et al 2017Geng et al , 2018. It can be seen that the AMO index exhibits a positive phase before the mid-1960s and after the mid-1990s, while showing a negative phase during the interim period, thus exhibiting an approximate inverse temporal evolution with the running correlations shown in the same figure.…”

Section: Decadal Variations Of Enso Combination Mode Amplitudementioning

confidence: 99%

Modulation of the Relationship between ENSO and Its Combination Mode by the Atlantic Multidecadal Oscillation

et al. 2020

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Recent studies demonstrated the existence of a conspicuous atmospheric combination mode (C-mode) originating from nonlinear interactions between El Niño–Southern Oscillation (ENSO) and the Pacific warm pool annual cycle (AC). Here we find that the C-mode exhibits prominent decadal amplitude variations during the ENSO decaying boreal spring season. It is revealed that the Atlantic multidecadal oscillation (AMO) can largely explain this waxing and waning in amplitude. A robust positive correlation between ENSO and the C-mode is detected during a negative AMO phase but not during a positive phase. Similar results can also be found in the relationship of ENSO with 1) the western North Pacific (WNP) anticyclone and 2) spring precipitation over southern China, both of which are closely associated with the C-mode. We suggest that ENSO property changes due to an AMO modulation play a crucial role in determining these decadal shifts. During a positive AMO phase, ENSO events are distinctly weaker than those in an AMO negative phase. In addition, El Niño events concurrent with a positive AMO phase tend to exhibit a westward-shifted sea surface temperature (SST) anomaly pattern. These SST characteristics during the positive AMO phase are both not conducive to the development of the meridionally asymmetric C-mode atmospheric circulation pattern and thus reduce the ENSO/C-mode correlation on decadal time scales. These observations can be realistically reproduced by a coupled general circulation model (CGCM) experiment in which North Atlantic SSTs are nudged to reproduce a 50-yr sinusoidally varying AMO evolution. Our conclusion carries important implications for understanding seasonally modulated ENSO dynamics and multiscale climate impacts over East Asia.

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A New Method for Interpreting Nonstationary Running Correlations and Its Application to the ENSO‐EAWM Relationship

Cited by 17 publications

References 28 publications

Impact of Atlantic multidecadal oscillation on interannual relationship between ENSO and East Asian early summer monsoon

Impact of Atlantic multidecadal oscillation on interannual relationship between ENSO and East Asian early summer monsoon

Interpreting the nonstationary relationship between El Niño–Southern Oscillation and the winter precipitation over southeast China

Modulation of the Relationship between ENSO and Its Combination Mode by the Atlantic Multidecadal Oscillation

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