scholarly journals Seasonal Synchronization of a Simple Stochastic Dynamical Model Capturing El Niño Diversity

2017 ◽  
Vol 30 (24) ◽  
pp. 10047-10066 ◽  
Author(s):  
Sulian Thual ◽  
Andrew Majda ◽  
Nan Chen
Keyword(s):  
El Niño ◽  
Cloud Cover ◽  
El Nino ◽  
Southern Oscillation ◽  
Eastern Pacific ◽  
Dynamical Model ◽  
Boreal Winter ◽  
Convective Activity ◽  
Central Pacific ◽  
Central Pacific El Niño

Recently, a simple stochastic dynamical model was developed that automatically captures the diversity and intermittency of El Niño–Southern Oscillation (ENSO) in nature, where state-dependent stochastic wind bursts and nonlinear advection of sea surface temperature (SST) are coupled to simple ocean–atmosphere processes that are otherwise deterministic, linear, and stable. In the present article, it is further shown that the model can reproduce qualitatively the ENSO synchronization (or phase locking) to the seasonal cycle in nature. This goal is achieved by incorporating a cloud radiative feedback that is derived naturally from the model’s atmosphere dynamics with no ad hoc assumptions and accounts in simple fashion for the marked seasonal variations of convective activity and cloud cover in the eastern Pacific. In particular, the weak convective response to SSTs in boreal fall favors the eastern Pacific warming that triggers El Niño events while the increased convective activity and cloud cover during the following spring contributes to the shutdown of those events by blocking incoming shortwave solar radiations. In addition to simulating the ENSO diversity with realistic non-Gaussian statistics in different Niño regions, the eastern Pacific moderate and super El Niño and the central Pacific El Niño and La Niña show a realistic chronology with a tendency to peak in boreal winter as well as decreased predictability in spring consistent with the persistence barrier in nature. The incorporation of other possible seasonal feedbacks in the model is also documented for completeness.

scholarly journals Diversity of the Madden–Julian Oscillation: Initiation Region Modulated by the Interaction between the Intraseasonal and Interannual Variabilities

2021 ◽  
Vol 34 (6) ◽  
pp. 2297-2318
Author(s):  
Daisuke Takasuka ◽  
Masaki Satoh
Keyword(s):  
El Niño ◽  
El Nino ◽  
Eastern Pacific ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Sst Variability ◽  
Circulation Patterns ◽  
The Difference

AbstractAs one of the aspects of the diversity of the Madden–Julian oscillation (MJO), the modulation of initiation regions of the boreal-winter MJO is studied in terms of the relationship between intraseasonal and interannual variabilities. MJOs are categorized as those initiating in the Indian Ocean (IO), Maritime Continent (MC), and western Pacific (WP), referred to herein as IO-MJOs, MC-MJOs, and WP-MJOs, respectively. The composite analyses for each MJO category using observational data reveal that the diversity of MJO initiation regions directly results from the modulation of areas where horizontal advective premoistening efficiently occurs via intraseasonal/synoptic-scale winds. This is supported by the difference in the zonal location of equatorial intraseasonal circulations established before MJO initiation, which is related to a spatial change in background convection and associated Walker circulations forced by interannual sea surface temperature (SST) variability. Compared to IO-MJOs (favored in the climatological background on average), MC-MJOs tend to be realized under the eastern-Pacific El Niño–like condition, as a result of eastward-shifted intraseasonal convection and circulation patterns induced by background suppressed convection in the eastern MC. WP-MJOs are frequently initiated under the central-Pacific El Niño–like and positive IO dipole–like conditions, in which the WP is selectively moistened with the aid of background enhanced (suppressed) convection over the WP (the southeastern IO and the central-to-eastern Pacific). This major tendency derived from sample-limited observations is verified by a set of 15-yr numerical experiments with a global nonhydrostatic MJO-permitting model under a perpetual boreal-winter condition where observation-based SSTs are prescribed.

Annual, Interannual, and Intraseasonal Variability of Tropical Tropopause Transition Layer Cirrus

2010 ◽  
Vol 67 (10) ◽  
pp. 3097-3112 ◽  
Author(s):  
Katrina S. Virts ◽  
John M. Wallace
Keyword(s):  
Annual Cycle ◽  
El Niño ◽  
Transition Layer ◽  
El Nino ◽  
Southern Oscillation ◽  
Cirrus Clouds ◽  
Boreal Winter ◽  
Central Pacific ◽  
Tropical Tropopause ◽  
The Pacific

Abstract Cloud fields based on the first three years of data from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission are used to investigate the relationship between cirrus within the tropical tropopause transition layer (TTL) and the Madden–Julian oscillation (MJO), the annual cycle, and El Niño–Southern Oscillation (ENSO). The TTL cirrus signature observed in association with the MJO resembles convectively induced, mixed Kelvin–Rossby wave solutions above the Pacific warm pool region. This signature is centered to the east of the peak convection and propagates eastward more rapidly than the convection; it exhibits a pronounced eastward tilt with height, suggestive of downward phase propagation and upward energy dispersion. A cirrus maximum is observed over equatorial Africa and South America when the enhanced MJO-related convection enters the western Pacific. Tropical-mean TTL cirrus is modulated by the MJO, with more than twice as much TTL cirrus fractional coverage equatorward of 10° latitude when the enhanced convection enters the Pacific than a few weeks earlier, when the convection is over the Indian Ocean. The annual cycle in cirrus clouds around the base of the TTL is equatorially asymmetric, with more cirrus observed in the summer hemisphere. Higher in the TTL, the annual cycle in cirrus clouds is more equatorially symmetric, with a maximum in the boreal winter throughout most of the tropics. The ENSO signature in TTL cirrus is marked by a zonal shift of the peak cloudiness toward the central Pacific during El Niño and toward the Maritime Continent during La Niña.

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.

scholarly journals Atmospheric torques and Earth's rotation: what drove the millisecond-level length-of-day response to the 2015–2016 El Niño?

2017 ◽  
Vol 8 (4) ◽  
pp. 1009-1017 ◽  
Author(s):  
Sébastien B. Lambert ◽  
Steven L. Marcus ◽  
Olivier de Viron
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Winter Season ◽  
Eastern Pacific ◽  
Earth’S Rotation ◽  
Length Of Day ◽  
Central Pacific ◽  
Earth's Rotation ◽  
Enso Events

Abstract. El Niño–Southern Oscillation (ENSO) events are classically associated with a significant increase in the length of day (LOD), with positive mountain torques arising from an east–west pressure dipole in the Pacific driving a rise of atmospheric angular momentum (AAM) and consequent slowing of the Earth's rotation. The large 1982–1983 event produced a lengthening of the day of about 0.9 ms, while a major ENSO event during the 2015–2016 winter season produced an LOD excursion reaching 0.81 ms in January 2016. By evaluating the anomaly in mountain and friction torques, we found that (i) as a mixed eastern–central Pacific event, the 2015–2016 mountain torque was smaller than for the 1982–1983 and 1997–1998 events, which were pure eastern Pacific events, and (ii) the smaller mountain torque was compensated for by positive friction torques arising from an enhanced Hadley-type circulation in the eastern Pacific, leading to similar AAM–LOD signatures for all three extreme ENSO events. The 2015–2016 event thus contradicts the existing paradigm that mountain torques cause the Earth rotation response for extreme El Niño events.

scholarly journals Relationships between Extratropical Sea Level Pressure Variations and the Central Pacific and Eastern Pacific Types of ENSO

2011 ◽  
Vol 24 (3) ◽  
pp. 708-720 ◽  
Author(s):  
Jin-Yi Yu ◽  
Seon Tae Kim
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Nodal Point ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Sst Anomalies

Abstract This study examines the linkages between leading patterns of interannual sea level pressure (SLP) variability over the extratropical Pacific (20°–60°N) and the eastern Pacific (EP) and central Pacific (CP) types of El Niño–Southern Oscillation (ENSO). The first empirical orthogonal function (EOF) mode of the extratropical SLP anomalies represents variations of the Aleutian low, and the second EOF mode represents the North Pacific Oscillation (NPO) and is characterized by a meridional SLP anomaly dipole with a nodal point near 50°N. It is shown that a fraction of the first SLP mode can be excited by both the EP and CP types of ENSO. The SLP response to the EP type is stronger and more immediate. The tropical–extratropical teleconnection appears to act more slowly for the CP ENSO. During the decay phase of EP events, the associated extratropical SLP anomalies shift from the first SLP mode to the second SLP mode. As the second SLP mode grows, subtropical SST anomalies are induced beneath via surface heat flux anomalies. The SST anomalies persist after the peak in strength of the second SLP mode, likely because of the seasonal footprinting mechanism, and lead to the development of the CP type of ENSO. This study shows that the CP ENSO is an extratropically excited mode of tropical Pacific variability and also suggests that the decay of an EP type of ENSO can lead to the onset of a CP type of ENSO with the aid of the NPO. This extratropical linking mechanism appears to be at work during the 1972, 1982, and 1997 strong El Niño events, which were all EP events and were all followed by strong CP La Niña events after the NPO was excited in the extratropics. This study concludes that extratropical SLP variations play an important role in exciting the CP type of ENSO and in linking the transitions from the EP to CP events.

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