scholarly journals Interannual and Decadal Variability in Tropical Pacific Chlorophyll from a Statistical Reconstruction: 1958–2008

2017 ◽  
Vol 30 (18) ◽  
pp. 7293-7315 ◽  
Author(s):  
Stephanie Schollaert Uz ◽  
Antonio J. Busalacchi ◽  
Thomas M. Smith ◽  
Michael N. Evans ◽  
Christopher W. Brown ◽  
...  
Keyword(s):  
El Niño ◽  
Decadal Variability ◽  
El Nino ◽  
Southern Oscillation ◽  
Ocean Color ◽  
Sea Surface ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Equatorial Undercurrent ◽  
Statistical Reconstruction

Abstract Historical understanding of marine biological dynamics has been limited by sparse in situ observations and the fact that dedicated ocean color satellite remote sensing only began in 1997. From these observations, it has become clear that physical oceanography controls biological variability over seasonal to interannual time scales. To quantify how multidecadal, climate-scale patterns impact biological productivity, the strong correlation with sea surface temperature and sea surface height is utilized to reconstruct a retrospective 51-yr time series of surface chlorophyll, the pigment measured by ocean color satellites. The canonical correlation analysis statistical reconstruction demonstrates greatest skill away from land and within about 10° of the equator where chlorophyll variance is greatest and predominantly associated with El Niño–Southern Oscillation dynamics. Differences in chlorophyll patterns between east or central Pacific El Niño events are observed, with larger declines east of 180° for east Pacific events and west of 180° for central Pacific events. Additionally, small but significant decadal variations in chlorophyll patterns are observed corresponding to the Pacific decadal oscillation. Decadal changes in chlorophyll west of 180° are consistent with increased stratification, whereas changes between 110°–140°W may be related to long-term shoaling of the nutrient-bearing equatorial undercurrent.

scholarly journals A Three-Region Conceptual Model for Central Pacific El Niño Including Zonal Advective Feedback

2018 ◽  
Vol 31 (13) ◽  
pp. 4965-4979 ◽  
Author(s):  
Xiang-Hui Fang ◽  
Mu Mu
Keyword(s):  
Surface Temperature ◽  
Conceptual Model ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Eastern Equatorial Pacific

The simple zonal two-region framework of the recharge paradigm can accurately manifest the traditional eastern Pacific (EP) type of El Niño–Southern Oscillation (ENSO), as its major warming center is located in the EP and the anomalous sea surface temperature (SST) changes monotonically from west to east along the equatorial Pacific. However, it cannot fully depict the variations of the central Pacific (CP) type of ENSO, whose major warming center is mainly situated in the CP. Therefore, to better investigate the characteristics of the CP type of ENSO, the recharge paradigm is extended to a three-region conceptual model to describe the entire western, central, and eastern equatorial Pacific. The results show that the extended conceptual model can depict the different variations between the CP and EP well. Specifically, with increasing magnitude of the zonal advective feedback over the CP (i.e., imitating the situation for CP ENSO), the period of the system and SST magnitude over the CP and EP both decrease. However, the decreasing amplitude is more intense over the EP, indicating an enlargement of the SST differences between the CP and EP. These results are all consistent with the observational characteristics of CP ENSO.

scholarly journals ENSO flavors in a tree-ring δ<sup>18</sup>O record of <i>Tectona grandis</i> from Indonesia

2015 ◽  
Vol 11 (10) ◽  
pp. 1325-1333 ◽  
Author(s):  
K. Schollaen ◽  
C. Karamperidou ◽  
P. Krusic ◽  
E. Cook ◽  
G. Helle
Keyword(s):  
Tree Ring ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Enso Events ◽  
Proxy Records ◽  
El Niño Events ◽  
El Nino Events

Abstract. Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900–2007) of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific) El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern Pacific) El Niño events. These results are consistent with the distinct impacts of the two ENSO flavors on Javanese precipitation, and illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics, as well as the potential of palaeoclimate proxy records from appropriately selected tropical regions for reconstructing past variability of. ENSO flavors.

scholarly journals A waveform skewness index for measuring time series nonlinearity and its applications to the ENSO–Indian monsoon relationship

2022 ◽  
Vol 29 (1) ◽  
pp. 1-15
Author(s):  
Justin Schulte ◽  
Frederick Policelli ◽  
Benjamin Zaitchik
Keyword(s):  
Time Series ◽  
El Niño ◽  
Indian Monsoon ◽  
El Nino ◽  
Southern Oscillation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Nonlinear Character ◽  
Indian Rainfall ◽  
Time Periods

Abstract. Many geophysical time series possess nonlinear characteristics that reflect the underlying physics of the phenomena the time series describe. The nonlinear character of times series can change with time, so it is important to quantify time series nonlinearity without assuming stationarity. A common way of quantifying the time evolution of time series nonlinearity is to compute sliding skewness time series, but it is shown here that such an approach can be misleading when time series contain periodicities. To remedy this deficiency of skewness, a new waveform skewness index is proposed for quantifying local nonlinearities embedded in time series. A waveform skewness spectrum is proposed for determining the frequency components that are contributing to time series waveform skewness. The new methods are applied to the El Niño–Southern Oscillation (ENSO) and the Indian monsoon to test a recently proposed hypothesis that states that changes in the ENSO–Indian monsoon relationship are related to ENSO nonlinearity. We show that the ENSO–Indian rainfall relationship weakens during time periods of high ENSO waveform skewness. The results from two different analyses suggest that the breakdown of the ENSO–Indian monsoon relationship during time periods of high ENSO waveform skewness is related to the more frequent occurrence of strong central Pacific El Niño events, supporting arguments that changes in the ENSO–Indian rainfall relationship are not solely related to noise.

Ocean dynamics are key to extratropical forcing of El Niño

2021 ◽  
pp. 1-34
Author(s):  
Soumi Chakravorty ◽  
Renellys C. Perez ◽  
Bruce T. Anderson ◽  
Sarah M. Larson ◽  
Benjamin S. Giese ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Ocean Dynamics ◽  
Positive Phase ◽  
Trade Wind ◽  
Atmospheric Variability ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Extratropical Forcing

AbstractThe El Niño/Southern Oscillation (ENSO) has been recently linked with extratropical-Pacific atmospheric variability. The two key mechanisms connecting the atmospheric variability of extratropical-Pacific with ENSO are the heat-flux driven “seasonal footprinting mechanism” (SFM) and the ocean-dynamics driven “trade wind charging” (TWC) mechanism. However, their relative contributions to ENSO are still unknown. Here we present modeling evidence that the positive phase of the SFM generates a weaker, short-lived central Pacific El Niño-like warming pattern in the fall, whereas the TWC positive phase leads to a wintertime eastern Pacific El Niño-like warming. When both mechanisms are active, a strong, persistent El Niño develops. While both mechanisms can trigger equatorial wind anomalies that generate an El Niño, the strength and persistence of the warming depends on the subsurface heat content buildup by the TWC mechanism. These results suggest that while dynamical-coupling associated with extratropical forcing is crucial to maintain an El Niño, thermodynamical-coupling is an extratropical source of El Niño diversity.

scholarly journals A Waveform Skewness Index for Measuring Time Series Nonlinearity and its Applications to the ENSO-Indian Monsoon Relationship

2020 ◽  
Author(s):  
Justin Schulte ◽  
Frederick Policelli ◽  
Benjamin Zaitchik
Keyword(s):  
Time Series ◽  
El Niño ◽  
Indian Monsoon ◽  
El Nino ◽  
Southern Oscillation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Nonlinear Character ◽  
Indian Rainfall ◽  
Time Periods

Abstract. Many geophysical time series possess nonlinear characteristics that reflect the underlying physics of the phenomena the time series describe. The nonlinear character of times series can change with time, so it is important to quantify time series nonlinearity without assuming stationarity. A common way to quantify the time-evolution of time series nonlinearity is to compute sliding skewness time series, but it is shown here that such an approach can be misleading when time series contain periodicities. To remedy this deficiency of skewness, a new waveform skewness index is proposed for quantifying local nonlinearities embedded in time series. A waveform skewness spectrum is proposed for determining the frequency components that are contributing to time series waveform skewness. The new methods are applied to the El Niño/ Southern Oscillation (ENSO) and the Indian monsoon to test a recently proposed hypothesis that states that changes in the ENSO-Indian Monsson relationship are related to ENSO nonlinearity. We show that the ENSO-Indian rainfall relationship weakens during time periods of high ENSO waveform skewness. The results from two different analyses suggest that the breakdown of the ENSO-Indian monsoon relationship during time periods of high ENSO waveform skewness is related to the more frequent occurrence of strong central Pacific El Niño events, supporting arguments that changes in the ENSO-Indian rainfall relationship are not solely related to noise.

Interdecadal Amplitude Modulation of El Niño–Southern Oscillation and Its Impact on Tropical Pacific Decadal Variability*

2013 ◽  
Vol 26 (18) ◽  
pp. 7280-7297 ◽  
Author(s):  
Tomomichi Ogata ◽  
Shang-Ping Xie ◽  
Andrew Wittenberg ◽  
De-Zheng Sun
Keyword(s):  
Amplitude Modulation ◽  
El Niño ◽  
Decadal Variability ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Sea Surface ◽  
El Nino Southern Oscillation ◽  
Pacific Decadal Variability ◽  
Decadal Scale

Abstract The amplitude of El Niño–Southern Oscillation (ENSO) displays pronounced interdecadal modulations in observations. The mechanisms for the amplitude modulation are investigated using a 2000-yr preindustrial control integration from the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (GFDL CM2.1). ENSO amplitude modulation is highly correlated with the second empirical orthogonal function (EOF) mode of tropical Pacific decadal variability (TPDV), which features equatorial zonal dipoles in sea surface temperature (SST) and subsurface temperature along the thermocline. Experiments with an ocean general circulation model indicate that both interannual and decadal-scale wind variability are required to generate decadal-scale tropical Pacific temperature anomalies at the sea surface and along the thermocline. Even a purely interannual and sinusoidal wind forcing can produce substantial decadal-scale effects in the equatorial Pacific, with SST cooling in the west, subsurface warming along the thermocline, and enhanced upper-ocean stratification in the east. A mechanism is proposed by which residual effects of ENSO could serve to alter subsequent ENSO stability, possibly contributing to long-lasting epochs of extreme ENSO behavior via a coupled feedback with TPDV.

scholarly journals Synchronized spatial shifts of Hadley and Walker circulations

2021 ◽  
Vol 12 (1) ◽  
pp. 121-132
Author(s):  
Kyung-Sook Yun ◽  
Axel Timmermann ◽  
Malte F. Stuecker
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Warm Pool ◽  
Sea Surface ◽  
Central Pacific

Abstract. The El Niño–Southern Oscillation (ENSO) influences the most extensive tropospheric circulation cells on our planet, known as Hadley and Walker circulations. Previous studies have largely focused on the effect of ENSO on the strength of these cells. However, what has remained uncertain is whether interannual sea surface temperature anomalies can also cause synchronized spatial shifts of these circulations. Here, by examining the spatiotemporal relationship between Hadley and Walker cells in observations and climate model experiments, we demonstrate that the seasonally evolving warm-pool sea surface temperature (SST) anomalies in the decay phase of an El Niño event generate a meridionally asymmetric Walker circulation response, which couples the zonal and meridional atmospheric overturning circulations. This process, which can be characterized as a phase-synchronized spatial shift in Walker and Hadley cells, is accompanied by cross-equatorial northwesterly low-level flow that diverges from an area of anomalous drying in the western North Pacific and converges towards a region with anomalous moistening in the southern central Pacific. Our results show that the SST-induced concurrent spatial shifts of the two circulations are climatically relevant as they can further amplify extratropical precipitation variability on interannual timescales.

scholarly journals ENSO flavors in a tree-ring δ<sup>18</sup>O record of <i>Tectona grandis</i> from Indonesia

2014 ◽  
Vol 10 (5) ◽  
pp. 3965-3987 ◽  
Author(s):  
K. Schollaen ◽  
C. Karamperidou ◽  
P. J. Krusic ◽  
E. R. Cook ◽  
G. Helle
Keyword(s):  
Tree Ring ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tectona Grandis ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Enso Events ◽  
El Niño Events ◽  
El Nino Events

Abstract. Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño–Southern Oscillation (ENSO) events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900–2007) of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific) El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern Pacific) El Niño events. These results are consistent with the distinct impacts of the two ENSO flavors on Javanese precipitation, and illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics.

scholarly journals A Skewed perspective of the Indian rainfall-ENSO Relationship

2019 ◽  
Author(s):  
Justin Schulte ◽  
Fredrick Policielli ◽  
Benjamin Zaitchik
Keyword(s):  
Time Series ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Wavelet Coherence ◽  
Drought Severity ◽  
Nonlinear Phenomenon ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Highly Nonlinear

Abstract. The application of higher-order wavelet analysis to India rainfall and the El Niño/Southern Oscillation (ENSO) is presented. An auto-bicoherence analysis is used to extract the frequency modes contributing to the skewness of India rainfall and ENSO. A nonlinear wavelet coherence method is proposed for diagnosing why the time-domain correlation between two time series temporally changes when at least one time series has changing nonlinear characteristics. The results indicate the India rainfall and ENSO are highly nonlinear phenomenon. It is also demonstrated that the sea surface temperature (SST) patterns associated with different nonlinear ENSO modes depend on the frequency components participating in the nonlinear phase coupling. The SST pattern associated with coupling between ENSO modes with periods of 31 and 15.5 months is reminiscent of a central Pacific El Niño and intensifies around 1995, contrasting with the coupling between the 62- and 31-month modes that became active around the 1970s ENSO regime shift. A nonlinear coherence analysis showed that the skewness of India rainfall is weakly correlated with that of 4 ENSO time series after the 1970s, indicating that increases in ENSO skewness after 1970's at least partially contributed to the weakening India rainfall-ENSO relationship in recent decades. The implication of this result is that the intensity of skewed El Niño events is likely to overestimate India drought severity, which was the case in the 1997 monsoon season, a time point when the nonlinear wavelet coherence between All-India rainfall and ENSO reached its lowest value in the 1871–2016 period.

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