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  • 1
    Online Resource
    Online Resource
    Sensitivity of ENSO to Stratification in a Recharge–Discharge Conceptual Model
    American Meteorological Society ; 2011
    In:  Journal of Climate Vol. 24, No. 16 ( 2011-08-15), p. 4332-4349
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 24, No. 16 ( 2011-08-15), p. 4332-4349
    Abstract: El Niño–Southern Oscillation (ENSO) is driven by large-scale ocean–atmosphere interactions in the equatorial Pacific and is sensitive to change in the mean state. Whereas conceptual models of ENSO usually consider the depth of the thermocline to be influential on the stability of ENSO, the observed changes in the depth of the 20°C isotherm are rather weak, on the order of approximately 5 m over the last decades. Conversely, change in stratification that affects both the intensity and sharpness of the thermocline can be pronounced. Here, the two-strip conceptual model of An and Jin is extended to include three parameters (i.e., the contribution of the first three baroclinic modes) that account for the main characteristics of the mean thermocline vertical structure. A stability analysis of the model is carried out that indicates that the model sustains a lower ENSO mode when the high-order baroclinic modes (M2 and M3) are considered. The sensitivity of the model solution to the coupling efficiency further indicates that, in the weak coupling regime, the model allows for several ocean basin modes at low frequency. The latter can eventually merge into a low-frequency and unstable mode representative of ENSO as the coupling efficiency increases. Also, higher baroclinic modes project more energy onto the ocean dynamics for the same input of wind forcing. Therefore, in this study’s model, a shallower, yet more intense mean thermocline may still sustain a strong (i.e., unstable) and low-frequency ENSO mode. Sensitivity tests to the strength of the two dominant feedbacks (thermocline vs zonal advection) indicate that the presence of high-order baroclinic modes favors the bifurcation from a low-frequency regime to a higher-frequency regime when the zonal advective feedback is enhanced. It is suggested that the proposed formalism can be used to interpret and measure the sensitivity of coupled general circulation models to climate change.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/2011JCLI4148.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2011
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  • 2
    Online Resource
    Online Resource
    El Niño–Southern Oscillation complexity
    Springer Science and Business Media LLC ; 2018
    In:  Nature Vol. 559, No. 7715 ( 2018-7), p. 535-545
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 559, No. 7715 ( 2018-7), p. 535-545
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/s41586-018-0252-6
    RVK:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
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  • 3
    Online Resource
    Online Resource
    Influence of Recent Stratification Changes on ENSO Stability in a Conceptual Model of the Equatorial Pacific
    American Meteorological Society ; 2013
    In:  Journal of Climate Vol. 26, No. 13 ( 2013-07-01), p. 4790-4802
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 26, No. 13 ( 2013-07-01), p. 4790-4802
    Abstract: Changes in the mean circulation of the equatorial Pacific Ocean partly control the strong decadal modulation of El Niño–Southern Oscillation (ENSO). This relationship is considered from the linear stability of a conceptual recharge/discharge model with parameters tuned from the observed mean state. Whereas decadal changes in the mean thermocline depth alone are usually considered in conceptual ENSO models, here focus is given to decadal changes in the mean stratification of the entire upper ocean (e.g., the mean thermocline depth, intensity, and thickness). Those stratification changes modify the projection of wind stress forcing momentum onto the gravest ocean baroclinic modes. Their influence on the simulated frequency and growth rate is comparable in intensity to the one of usual thermodynamic and atmospheric feedbacks, while they have here a secondary effect on the spatial structure and propagation of SST anomalies. This sensitivity is evidenced in particular for the climate shift of the 1970s in the Simple Ocean Data Assimilation (SODA) dataset, as well as in a preindustrial simulation of the Geophysical Fluid Dynamics Laboratory (GFDL) model showing stratification changes similar to the ones after 2000. Despite limitations of the linear stability approach, conclusions on the sensitivity to stratification may be extended to interpret the modulation and diversity of ENSO in observations and in general circulation models.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-12-00363.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 4
    Online Resource
    Online Resource
    ENSO Feedbacks and Associated Time Scales of Variability in a Multimodel Ensemble
    American Meteorological Society ; 2010
    In:  Journal of Climate Vol. 23, No. 12 ( 2010-06-15), p. 3181-3204
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 23, No. 12 ( 2010-06-15), p. 3181-3204
    Abstract: The background state of the equatorial Pacific determines the prevalence of a “slow” recharge oscillator-type ENSO over a “fast” quasi-biennial surface-driven ENSO. The first is controlled to a large extent by the thermocline feedback, whereas the latter is related to enhanced zonal advective feedback. In this study, dynamical diagnostics are used to investigate the relative importance of these two feedbacks in the Coupled Model Intercomparison Project and its relation with the differences in ENSO-like variability among the models. The focus is on the role of the mean oceanic surface circulation in controlling the relative weight of the two feedbacks. By the means of an intermediate-type ocean model of the tropical Pacific “tuned” from the coupled general circulation model (CGCM) outputs, the contribution of the advection terms (vertical versus zonal) to the rate of SST change is estimated. A new finding is that biases in the advection terms are to a large extent related to the biases in the mean surface circulation. The latter are used to infer the dominant ENSO feedback for each CGCM. This allows for the classification of the CGCMs into three groups that account for the dominant feedback process of the ENSO cycle: horizontal advection (mainly in the western Pacific), vertical advection (mainly in the eastern Pacific), and the combination of both mechanisms. Based on such classification, the analysis also reveals that the models exhibit distinctive behavior with respect to the characteristics of ENSO: for most models, an enhanced (diminished) contribution of the zonal advective feedback is associated with faster (slower) ENSO and a tendency toward a cooler (warmer) mean state in the western-to-central Pacific Ocean. The results support the interpretation that biases in the mean state are sustained/maintained by the privileged mode of variability associated with the dominant feedback mechanism in the models. In particular, the models having a dominant zonal advective feedback exhibit significant cold SST asymmetry (or negative skewness) in the western equatorial Pacific.
    Type of Medium: Online Resource
    ISSN: 1520-0442 , 0894-8755
    URL: Article
    DOI: 10.1175/2010JCLI2830.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2010
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 5
    Online Resource
    Online Resource
    Author Correction: El Niño–Southern Oscillation complexity
    Springer Science and Business Media LLC ; 2019
    In:  Nature Vol. 567, No. 7746 ( 2019-3), p. E3-E3
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 567, No. 7746 ( 2019-3), p. E3-E3
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/s41586-019-0994-9
    RVK:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
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  • 6
    Online Resource
    Online Resource
    ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing
    American Geophysical Union (AGU) ; 2018
    In:  Reviews of Geophysics Vol. 56, No. 1 ( 2018-03), p. 185-206
    Details
    In: Reviews of Geophysics, American Geophysical Union (AGU), Vol. 56, No. 1 ( 2018-03), p. 185-206
    Abstract: The character of ENSO as well as the ocean mean state has changed since the 1990s, resulting in changes in ENSO atmospheric teleconnections Changes in ENSO teleconnection patterns have affected their predictability and the statistics of extreme events Climate models suggest that changes in the mean atmospheric circulation will affect ENSO teleconnections in the 21st century
    Type of Medium: Online Resource
    ISSN: 8755-1209 , 1944-9208
    URL: Issue
    URL: Article
    DOI: 10.1002/rog.v56.1
    DOI: 10.1002/2017RG000568
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2018
    detail.hit.zdb_id: 2035391-1
    detail.hit.zdb_id: 209852-0
    detail.hit.zdb_id: 209853-2
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Interactive Feedback between the Tropical Pacific Decadal Oscillation and ENSO in a Coupled General Circulation Model
    American Meteorological Society ; 2009
    In:  Journal of Climate Vol. 22, No. 24 ( 2009-12-15), p. 6597-6611
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 22, No. 24 ( 2009-12-15), p. 6597-6611
    Abstract: The output from a coupled general circulation model (CGCM) is used to develop evidence showing that the tropical Pacific decadal oscillation can be driven by an interaction between the El Niño–Southern Oscillation (ENSO) and the slowly varying mean background climate state. The analysis verifies that the decadal changes in the mean states are attributed largely to decadal changes in ENSO statistics through nonlinear rectification. This is seen because the time evolutions of the first principal component analysis (PCA) mode of the decadal-varying tropical Pacific SST and the thermocline depth anomalies are significantly correlated to the decadal variations of the ENSO amplitude (also skewness). Its spatial pattern resembles the residuals of the SST and thermocline depth anomalies after there is uneven compensation from El Niño and La Niña events. In addition, the stability analysis of a linearized intermediate ocean–atmosphere coupled system, for which the background mean states are specified, provides qualitatively consistent results compared to the CGCM in terms of the relationship between changes in the background mean states and the characteristics of ENSO. It is also shown from the stability analysis as well as the time integration of a nonlinear version of the intermediate coupled model that the mean SST for the high-variability ENSO decades acts to intensify the ENSO variability, while the mean thermocline depth for the same decades acts to suppress the ENSO activity. Thus, there may be an interactive feedback consisting of a positive feedback between the ENSO activity and the mean state of the SST and a negative feedback between the ENSO activity and the mean state of the thermocline depth. This feedback may lead to the tropical decadal oscillation, without the need to invoke any external mechanisms.
    Type of Medium: Online Resource
    ISSN: 1520-0442 , 0894-8755
    URL: Article
    DOI: 10.1175/2009JCLI2782.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2009
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  • 8
    Online Resource
    Online Resource
    Interaction between Near-Annual and ENSO Modes in a CGCM Simulation: Role of the Equatorial Background Mean State
    American Meteorological Society ; 2007
    In:  Journal of Climate Vol. 20, No. 6 ( 2007-03-15), p. 1035-1052
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 20, No. 6 ( 2007-03-15), p. 1035-1052
    Abstract: A 260-yr-long coupled general circulation model (CGCM) simulation is used to investigate the interaction between ENSO mode and near-annual variability and its sensitivity to the equatorial background mean stratification and seasonal cycles. Although the thermocline mean vertical structure of the model favors the high-order baroclinic modes that are associated with the slow time scales of the coupled variability, the simulated ENSO oscillates at a dominant quasi-biennial frequency. Biases of the climatological velocity field are favorable to the dominance of the zonal advective feedback over the thermocline feedback, the model exhibiting an overenergetic westward seasonal zonal current in the central-western equatorial Pacific, and an upwelling rate that is about half the observations. This sets the conditions for the enhancement of a near-annual mode that is observed to oscillate at an 8-month period in the model. Using an intermediate coupled model of the tropical Pacific where the climatological fields are prescribed to the ones derived from the CGCM, it is demonstrated that the quasi-biennial ENSO variability simulated by the CGCM is mostly due to the biases in the climatological currents of the CGCM. These biases favor the dominance of the fast “zonal advective feedback” over the slow “thermocline feedback” in the coupled system and enhance a fast coupled basin mode. This fast mode differs from the theoretical Pacific Ocean basin mode in that, besides mean temperature advection by the zonal current anomalies, it is also driven by anomalous temperature advection by the total current. Results suggest that the near-annual mode destabilizes the ENSO mode to produce overenergetic quasi-biennial oscillations in the model. It also contributes to the ENSO asymmetry and the cold bias of the CGCM mean state by nonlinear accumulation of temperature zonal advection, which works toward the cold in the western Pacific more than the warm in the east. It is suggested that the model equilibrium results from the interaction between the ENSO mode, the near-annual mode, and the mean state.
    Type of Medium: Online Resource
    ISSN: 1520-0442 , 0894-8755
    URL: Article
    DOI: 10.1175/JCLI4060.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2007
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  • 9
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    North Atlantic Warming Hole Modulates Interhemispheric Asymmetry of Future Temperature and Precipitation
    American Geophysical Union (AGU) ; 2024
    In:  Earth's Future Vol. 12, No. 6 ( 2024-06)
    Details
    In: Earth's Future, American Geophysical Union (AGU), Vol. 12, No. 6 ( 2024-06)
    Abstract: Future warming hole changes in Coupled Model Intercomparison Phase 6 models affect the interhemispheric asymmetry of temperature Greater warming in the warming hole increases the non‐radiative fluxes in the Northern Hemisphere, leading to an increase in the interhemispheric asymmetry The warming hole affects future global precipitation by modulating the location of the ITCZ
    Type of Medium: Online Resource
    ISSN: 2328-4277 , 2328-4277
    URL: Article
    DOI: 10.1029/2023EF004146
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2024
    detail.hit.zdb_id: 2746403-9
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