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  • 1
    Online Resource
    Online Resource
    A theoretical model to analyze the Central to Eastern Pacific El Niño continuum
    Elsevier BV ; 2018
    In:  Ocean Modelling Vol. 130 ( 2018-10), p. 140-159
    Details
    In: Ocean Modelling, Elsevier BV, Vol. 130 ( 2018-10), p. 140-159
    Type of Medium: Online Resource
    ISSN: 1463-5003
    URL: Article
    DOI: 10.1016/j.ocemod.2018.07.006
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
    detail.hit.zdb_id: 1126496-2
    detail.hit.zdb_id: 1498544-5
    SSG: 14
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  • 2
    Online Resource
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    A Tropical Stochastic Skeleton Model for the MJO, El Niño, and Dynamic Walker Circulation: A Simplified GCM
    American Meteorological Society ; 2018
    In:  Journal of Climate Vol. 31, No. 22 ( 2018-11-15), p. 9261-9282
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 31, No. 22 ( 2018-11-15), p. 9261-9282
    Abstract: A simple dynamical stochastic model for the tropical ocean atmosphere is proposed that captures qualitatively major intraseasonal to interannual processes altogether including El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation (MJO), the associated wind bursts, and the background dynamic Walker circulation. Such a model serves as a prototype “skeleton” for general circulation models (GCMs) that solve similar dynamical interactions across several spatiotemporal scales but usually show common and systematic biases in representing tropical variability as a whole. The most salient features of ENSO, the wind bursts, and the MJO are captured altogether including their overall structure, evolution, and fundamental interactions in addition to their intermittency, diversity, and energy distribution across scales. Importantly, the intraseasonal wind bursts and the MJO are here solved dynamically, which provides their upscale contribution to the interannual flow as well as their modulation in return in a more explicit way. This includes a realistic onset of El Niño events with increased wind bursts and MJO activity starting in the Indian Ocean to the western Pacific and expanding eastward toward the central Pacific, as well as significant interannual modulation of the characteristics of intraseasonal variability. A hierarchy of cruder model versions is also analyzed in order to highlight fundamental concepts related to the treatment of multiple time scales, main convective nonlinearities, and the associated stochastic convective parameterizations. The model developed here also should be useful to diagnose, analyze, and help eliminate the strong tropical biases that exist in current operational models.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-18-0263.1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 3
    Online Resource
    Online Resource
    A Suite of Skeleton Models for the MJO with Refined Vertical Structure
    Portico ; 2015
    In:  Mathematics of Climate and Weather Forecasting Vol. 1, No. 1 ( 2015-01-30)
    Details
    In: Mathematics of Climate and Weather Forecasting, Portico, Vol. 1, No. 1 ( 2015-01-30)
    Abstract: The Madden-Julian oscillation (MJO) is the dominant mode of variability in the tropical atmosphere on intraseasonal timescales and planetary spatial scales. The skeleton model is a minimal dynamical model that recovers robustly the most fundamental MJO features of (I) a slow eastward speed of roughly 5 ms−1, (II) a peculiar dispersion relation with dw/dk ≈ 0, and (III) a horizontal quadrupole vortex structure. This model depicts the MJO as a neutrally-stable atmosphericwave that involves a simple multiscale interaction between planetary dry dynamics, planetary lower-tropospheric moisture and the planetary envelope of synoptic-scale activity. Here we propose and analyze a suite of skeleton models that qualitatively reproduce the refined vertical structure of the MJO in nature. This vertical structure consists of a planetary envelope of convective activity transitioning from the congestus to the deep to the stratiform type, in addition to a front-to-rear (i.e. tilted) structure of heating, moisture, winds and temperature. A first example of skeleton model achieving this goal has been considered recently in work by the authors. The construction of such a model satisfies an energy conservation principle, such that its solutions at the intraseasonal-planetary scale remain neutrally stable. Here, additional classes of skeleton models are constructed based on the same principle. In particular, those new models are more realistic then the former one as they consider fully coupled interactions between the planetary dry dynamics of the first and second baroclinic mode and the details of the vertical structure of moisture and convective activity. All models reproduce qualitatively the refined vertical structure of the MJO. In addition,when considered with a simple stochastic parametrization for the unresolved details of synopticscale activity, all models show intermittent initiation, propagation and shut down of MJO wave trains, as in previous studies.
    Type of Medium: Online Resource
    ISSN: 2353-6438
    URL: Article
    DOI: 10.1515/mcwf-2015-0004
    Language: Unknown
    Publisher: Portico
    Publication Date: 2015
    detail.hit.zdb_id: 2863553-X
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  • 4
    Online Resource
    Online Resource
    Observations and Mechanisms of a Simple Stochastic Dynamical Model Capturing El Niño Diversity
    American Meteorological Society ; 2018
    In:  Journal of Climate Vol. 31, No. 1 ( 2018-01-01), p. 449-471
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 31, No. 1 ( 2018-01-01), p. 449-471
    Abstract: El Niño–Southern Oscillation (ENSO) has significant impact on global climate and relevance for seasonal forecasts. Recently, a simple modeling framework was developed that captures the ENSO diversity, where state-dependent stochastic wind bursts and nonlinear advection of sea surface temperature are coupled to a simple ocean–atmosphere model that is otherwise deterministic, linear, and stable. In this article, the coupled model is compared with observations using reanalysis data over the last 34 yr, where the observed non-Gaussian statistics and the overall mechanisms of ENSO are both captured by the model. Then the formation mechanisms of both the central Pacific (CP) and the traditional El Niño in the model are systematically studied. First, ocean Rossby waves induced by easterly trade wind anomalies facilitate the heat content buildup. Then the reflected ocean Kelvin waves and the nonlinear advection lead to positive SST anomalies in the CP region and create a CP El Niño. Second, two formation mechanisms are revealed for the traditional El Niño, including the super (extreme) El Niño. The first mechanism indicates a preferred wind structure with easterly wind bursts (EWBs) leading westerly wind bursts (WWBs), where the EWBs build up heat content and then the WWBs trigger the El Niño. The second mechanism links the two types of El Niño, where a CP El Niño favors a heat content buildup and the advent of a traditional El Niño. This article also highlights the mechanisms of La Niña formation and El Niño termination.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    URL: Article
    DOI: 10.1175/JCLI-D-16-0880.1
    DOI: 10.1175/JCLI-D-16-0880.s1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 5
    Online Resource
    Online Resource
    Asymmetric intraseasonal events in the stochastic skeleton MJO model with seasonal cycle
    Springer Science and Business Media LLC ; 2015
    In:  Climate Dynamics Vol. 45, No. 3-4 ( 2015-8), p. 603-618
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 45, No. 3-4 ( 2015-8), p. 603-618
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-014-2256-8
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2015
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    Statistical occurrence and mechanisms of the 2014–2016 delayed super El Niño captured by a simple dynamical model
    Springer Science and Business Media LLC ; 2019
    In:  Climate Dynamics Vol. 52, No. 3-4 ( 2019-2), p. 2351-2366
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 52, No. 3-4 ( 2019-2), p. 2351-2366
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-018-4265-5
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    A skeleton model for the MJO with refined vertical structure
    Springer Science and Business Media LLC ; 2016
    In:  Climate Dynamics Vol. 46, No. 9-10 ( 2016-5), p. 2773-2786
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 46, No. 9-10 ( 2016-5), p. 2773-2786
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-015-2731-x
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 8
    Online Resource
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    Evaluating MJO event initiation and decay in the skeleton model using an RMM‐like index
    American Geophysical Union (AGU) ; 2015
    In:  Journal of Geophysical Research: Atmospheres Vol. 120, No. 22 ( 2015-11-27)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 120, No. 22 ( 2015-11-27)
    Abstract: An RMM‐like index was created for the skeleton model that mimics observations Stochasticity helps improve MJO initiation and termination event statistics The skeleton model produces more realistic MJOs when forced with observed SSTs
    Type of Medium: Online Resource
    ISSN: 2169-897X , 2169-8996
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrd.v120.22
    DOI: 10.1002/2015JD023916
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2015
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 2969341-X
    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    Simple stochastic model for El Niño with westerly wind bursts
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 37 ( 2016-09-13), p. 10245-10250
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 37 ( 2016-09-13), p. 10245-10250
    Abstract: Atmospheric wind bursts in the tropics play a key role in the dynamics of the El Niño Southern Oscillation (ENSO). A simple modeling framework is proposed that summarizes this relationship and captures major features of the observational record while remaining physically consistent and amenable to detailed analysis. Within this simple framework, wind burst activity evolves according to a stochastic two-state Markov switching–diffusion process that depends on the strength of the western Pacific warm pool, and is coupled to simple ocean–atmosphere processes that are otherwise deterministic, stable, and linear. A simple model with this parameterization and no additional nonlinearities reproduces a realistic ENSO cycle with intermittent El Niño and La Niña events of varying intensity and strength as well as realistic buildup and shutdown of wind burst activity in the western Pacific. The wind burst activity has a direct causal effect on the ENSO variability: in particular, it intermittently triggers regular El Niño or La Niña events, super El Niño events, or no events at all, which enables the model to capture observed ENSO statistics such as the probability density function and power spectrum of eastern Pacific sea surface temperatures. The present framework provides further theoretical and practical insight on the relationship between wind burst activity and the ENSO.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1612002113
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Seasonal Synchronization of a Simple Stochastic Dynamical Model Capturing El Niño Diversity
    American Meteorological Society ; 2017
    In:  Journal of Climate Vol. 30, No. 24 ( 2017-12), p. 10047-10066
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 30, No. 24 ( 2017-12), p. 10047-10066
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-17-0174.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2017
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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