Simple stochastic dynamical models capturing the statistical diversity of El Niño Southern Oscillation

Nan Chen, Andrew J. Majda

Research output: Contribution to journalArticle

Abstract

The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean-atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model.

Original languageEnglish (US)
Pages (from-to)1468-1473
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number7
DOIs
StatePublished - Feb 14 2017

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Southern Oscillation
sea surface temperature
trade wind
parameterization
anomaly
Walker circulation
warm pool
westerly
temperature gradient
global climate
advection
atmosphere
ocean
prediction
modeling

Keywords

  • Atmospheric wind bursts
  • Easterly trade wind
  • Non-Gaussian statistical features
  • Nonlinear zonal advection
  • Three-state stochastic Markov jump process

ASJC Scopus subject areas

  • General

Cite this

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title = "Simple stochastic dynamical models capturing the statistical diversity of El Ni{\~n}o Southern Oscillation",
abstract = "The El Ni{\~n}o Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean-atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Ni{\~n}o, the super El Ni{\~n}o, and the central Pacific (CP) El Ni{\~n}o as well as the La Ni{\~n}a with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Ni{\~n}os is followed by a super El Ni{\~n}o and then a La Ni{\~n}a. Importantly, both the variance and the non-Gaussian statistical features in different Ni{\~n}o regions spanning from the western to the eastern Pacific are captured by the coupled model.",
keywords = "Atmospheric wind bursts, Easterly trade wind, Non-Gaussian statistical features, Nonlinear zonal advection, Three-state stochastic Markov jump process",
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AB - The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean-atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model.

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