Understanding Diverse Model Projections of Future Extreme El Niño

2021 ◽  
Vol 34 (2) ◽  
pp. 449-464
Author(s):  
Samantha Stevenson ◽  
Andrew T. Wittenberg ◽  
John Fasullo ◽  
Sloan Coats ◽  
Bette Otto-Bliesner
Keyword(s):  
El Niño ◽  
El Nino ◽  
Coupled Model ◽  
Equatorial Pacific ◽  
Model Intercomparison ◽  
Sst Variability ◽  
Eastern Equatorial Pacific ◽  
Intercomparison Project ◽  
Local Warming ◽  
Extreme El Niño

AbstractThe majority of future projections in the Coupled Model Intercomparison Project (CMIP5) show more frequent exceedances of the 5 mm day−1 rainfall threshold in the eastern equatorial Pacific rainfall during El Niño, previously described in the literature as an increase in “extreme El Niño events”; however, these exceedance frequencies vary widely across models, and in some projections actually decrease. Here we combine single-model large ensemble simulations with phase 5 of the Coupled Model Intercomparison Project (CMIP5) to diagnose the mechanisms for these differences. The sensitivity of precipitation to local SST anomalies increases consistently across CMIP-class models, tending to amplify extreme El Niño occurrence; however, changes to the magnitude of ENSO-related SST variability can drastically influence the results, indicating that understanding changes to SST variability remains imperative. Future El Niño rainfall intensifies most in models with 1) larger historical cold SST biases in the central equatorial Pacific, which inhibit future increases in local convective cloud shading, enabling more local warming; and 2) smaller historical warm SST biases in the far eastern equatorial Pacific, which enhance future reductions in stratus cloud, enabling more local warming. These competing mechanisms complicate efforts to determine whether CMIP5 models under- or overestimate the future impacts of climate change on El Niño rainfall and its global impacts. However, the relation between future projections and historical biases suggests the possibility of using observable metrics as “emergent constraints” on future extreme El Niño, and a proof of concept using SSTA variance, precipitation sensitivity to SST, and regional SST trends is presented.

scholarly journals Linking Centennial Surface Warming Patterns in the Equatorial Pacific to the Relative Strengths of the Walker and Hadley Circulations

2014 ◽  
Vol 71 (9) ◽  
pp. 3454-3464 ◽  
Author(s):  
Jian Ma ◽  
Jin-Yi Yu
Keyword(s):  
El Niño ◽  
El Nino ◽  
Coupled Model ◽  
Walker Circulation ◽  
Equatorial Pacific ◽  
Bjerknes Feedback ◽  
Central Pacific ◽  
Surface Warming ◽  
Temperature Feedback ◽  
Intercomparison Project

Abstract This study analyzes representative concentration pathway 4.5 projections by 18 models from phase 5 of the Coupled Model Intercomparison Project to show that surface warming patterns in the equatorial Pacific during the twenty-first century (centennial warming) are influenced by the relative strengths of the Walker and Hadley circulations. The stronger the Hadley (Walker) circulation is, the greater the surface warming in the central Pacific (CP) [eastern Pacific (EP)]. The EP warming is associated with the Bjerknes feedback, while the CP warming is associated with the wind–evaporation–sea surface temperature feedback. This atmospheric circulation influence on the centennial warming is similar to that found for the EP and CP El Niño. This suggests a methodology to constrain the estimate of the projected surface warming patterns in the equatorial Pacific using recent El Niño activity. The constraint indicates that the “most likely” centennial warming patterns have a maximum in the EP and are 39% weaker than the warming projected by the 18-model mean. The most-likely projection also shows alternating stronger and weaker warming in the subtropical North Pacific, which is not predicted by the 18-model mean projection. Nevertheless, the two projections agree on the minimum warming in the southeastern subtropical Pacific.

El Niño–La Niña Asymmetry in the Coupled Model Intercomparison Project Simulations*

2005 ◽  
Vol 18 (14) ◽  
pp. 2617-2627 ◽  
Author(s):  
Soon-Il An ◽  
Yoo-Geun Ham ◽  
Jong-Seong Kug ◽  
Fei-Fei Jin ◽  
In-Sik Kang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Coupled Model ◽  
La Niña ◽  
Model Intercomparison ◽  
Decadal Change ◽  
Tropical Eastern Pacific ◽  
Enso Events ◽  
La Nina ◽  
Intercomparison Project

Abstract The El Niño–La Niña asymmetry was estimated in the 10 different models participating in the Coupled Model Intercomparison Project (CMIP). Large differences in the “asymmetricity” (a variance-weighted skewness) of SST anomalies are found between models and observations. Most of the coupled models underestimate the nonlinearity and only a few exhibit the positively skewed SST anomalies over the tropical eastern Pacific as seen in the observation. A significant association between the nonlinear dynamical heating (NDH) and asymmetricity in the model–ENSO indices is found, inferring that asymmetricity is caused mainly by NDH. Among the 10 models, one coupled GCM simulates the asymmetricity of the tropical SST realistically, and its simulation manifests a strong relationship between the intensity and the propagating feature of ENSO—the strong ENSO events moving eastward and the weak ENSO events moving westward—which is consistent with the observation. Interestingly, the coupled general circulation models, of which the ocean model is based on the one used by Bryan and Cox, commonly showed the reasonably positive skewed ENSO. The decadal changes in the skewness, variance, and NDH of the model-simulated ENSO are also observed. These three quantities over the tropical eastern Pacific are significantly correlated to each other, indicating that the decadal change in ENSO variability is closely related to the nonlinear process of ENSO. It is also found that these decadal changes in ENSO variability are related to the decadal variation in the tropical Pacific SST, implying that the decadal change in the El Niño–La Niña asymmetry could manifest itself as a rectified change in the background state.

scholarly journals Caracterização dos Diferentes Tipos de El Niño e seus Impactos na América do Sul a Partir de Dados Observados e Modelados

2019 ◽  
Vol 34 (1) ◽  
pp. 43-67
Author(s):  
Juarez Viegas ◽  
Rita Valéria Andreoli ◽  
Mary Toshie Kayano ◽  
Luiz Antonio Candido ◽  
Rodrigo Augusto Ferreira de Souza ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Coupled Model ◽  
System Model ◽  
Earth System ◽  
Model Intercomparison ◽  
Environmental Model ◽  
Global Environmental ◽  
Intercomparison Project ◽  
Hadley Centre

Resumo Estudos recentes têm apontado para a existência de dois tipos de eventos de El Niño (EN): EN do Pacífico oriental ou Canônico (EP, sigla em inglês) e EN do Pacífico Central ou Modoki (CP, sigla em inglês). Neste estudo, foram utilizados dados observados e de três modelos do Coupled Model Intercomparison Project phase 5 (CMIP5) para avaliar o impacto dos dois tipos de EN na precipitação da América do Sul desde o trimestre de Junho-Agosto do ano inicial do evento até Março-Maio do ano seguinte. O modelo do Centre National de Recherches Météorologiques (CNRM-CM5) apresentou o melhor desempenho para reproduzir os padrões anômalos observados de TSM para os tipos de EN CP e EP. O padrão anômalo da precipitação observada associado a eventos EN foi mais marcante durante o verão austral. No caso do EN EP, tal padrão caracterizou-se por precipitação acima (abaixo) da normal no sudeste (norte/noroeste) da América do Sul. Este padrão foi reproduzido pelos modelos CNRM-CM5 e Hadley Centre Global Environmental Model (HadGEM2-ES). O Max Plank Institute Earth System model (MPI-ESM-LR) reproduziu a redução de chuva no norte, porém não reproduziu o aumento anômalo no sudeste e redução no noroeste do continente. No caso do EN CP, o impacto observado nas chuvas da América do Sul durante o verão caracterizou-se por escassez (excesso) no norte/noroeste (sudeste). Este padrão foi reproduzido pelos modelos, entretanto, os modelos HadGEM2-ES e MPI-ESM-LR mostraram índices pluviométricos no nordeste do Brasil menores do que os observados. As diferenças na representação dos padrões de teleconexões em resposta ao EN explicam as diferenças entre os padrões simulados.

scholarly journals Effects of Excessive Equatorial Cold Tongue Bias on the Projections of Tropical Pacific Climate Change. Part II: The Extreme El Niño Frequency in CMIP5 Multi-Model Ensemble

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 851
Author(s):  
Gen Li ◽  
Zhiyuan Zhang ◽  
Bo Lu
Keyword(s):  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Equatorial Pacific ◽  
Western Pacific ◽  
Warming Pattern ◽  
El Niño Events ◽  
Rcp 8.5 ◽  
Extreme El Niño ◽  
El Nino Events

Under increased greenhouse gas (GHG) forcing, climate models tend to project a warmer sea surface temperature in the eastern equatorial Pacific than in the western equatorial Pacific. This El Niño-like warming pattern may induce an increase in the projected occurrence frequency of extreme El Niño events. The current models, however, commonly suffer from an excessive westward extension of the equatorial Pacific cold tongue accompanied by insufficient equatorial western Pacific precipitation. By comparing the Representative Concentration Pathway (RCP) 8.5 experiments with the historical simulations based on the Coupled Model Intercomparison Project phase 5 (CMIP5), a “present–future” relationship among climate models was identified: models with insufficient equatorial western Pacific precipitation error would have a weaker mean El Niño-like warming pattern as well as a lower increase in the frequency of extreme El Niño events under increased GHG forcing. Using this “present–future” relationship and the observed precipitation in the equatorial western Pacific, this study calibrated the climate projections in the tropical Pacific. The corrected projections showed a stronger El Niño-like pattern of mean changes in the future, consistent with our previous study. In particular, the projected increased occurrence of extreme El Niño events under RCP 8.5 forcing are underestimated by 30–35% in the CMIP5 multi-model ensemble before the corrections. This implies an increased risk of the El Niño-related weather and climate disasters in the future.

scholarly journals Contributions of Atmosphere–Ocean Interaction and Low-Frequency Variation to Intensity of Strong El Niño Events since 1979

2019 ◽  
Vol 32 (5) ◽  
pp. 1381-1394 ◽  
Author(s):  
Xiaofan Li ◽  
Zeng-Zhen Hu ◽  
Bohua Huang
Keyword(s):  
El Niño ◽  
Time Scale ◽  
El Nino ◽  
Deep Convection ◽  
Surface Wind ◽  
Equatorial Pacific ◽  
Frequency Variation ◽  
Low Level ◽  
Eastern Equatorial Pacific ◽  
Ocean Coupling

Evolutions of oceanic and atmospheric anomalies in the equatorial Pacific during four strong El Niños (1982/83, 1991/92, 1997/98, and 2015/16) since 1979 are compared. The contributions of the atmosphere–ocean coupling to El Niño–associated sea surface temperature anomalies (SSTA) are identified and their association with low-level winds as well as different time-scale variations is examined. Although overall SSTA in the central and eastern equatorial Pacific is strongest and comparable in the 1997/98 and 2015/16 El Niños, the associated subsurface ocean temperature as well as deep convection and surface wind stress anomalies in the central and eastern equatorial Pacific are weaker during 2015/16 than that during 1997/98. That may be associated with a variation of the wind–SST and wind–thermocline interactions. Both the wind–SST and wind–thermocline interactions play a less important role during 2015/16 than during 1997/98. Such differences are associated with the differences of the low-level westerly wind as well as the contribution of different time-scale variations in different events. Similar to the interannual time-scale variation, the intraseasonal–interseasonal time-scale component always has positive contributions to the intensity of all four strong El Niños. Interestingly, the role of the interdecadal-trend time-scale component varies with event. The contribution is negligible during the 1982/83 El Niño, negative during the 1997/98 El Niño, and positive during the 1991/92 and 2015/16 El Niños. Thus, in addition to the atmosphere–ocean coupling at intraseasonal to interannual time scales, interdecadal and longer time-scale variations may play an important and sometimes crucial role in determining the intensity of El Niño.

Adjoint Sensitivity of the Niño-3 Surface Temperature to Wind Forcing

2011 ◽  
Vol 24 (16) ◽  
pp. 4480-4493 ◽  
Author(s):  
Xuebin Zhang ◽  
Bruce Cornuelle ◽  
Dean Roemmich
Keyword(s):  
Surface Temperature ◽  
Wind Stress ◽  
El Niño ◽  
El Nino ◽  
Sensitivity Study ◽  
Enso Event ◽  
Equatorial Pacific ◽  
Wind Forcing ◽  
Adjoint Sensitivity ◽  
Eastern Equatorial Pacific

Abstract The evolution of sea surface temperature (SST) over the eastern equatorial Pacific plays a significant role in the intense tropical air–sea interaction there and is of central importance to the El Niño–Southern Oscillation (ENSO) phenomenon. Effects of atmospheric fields (especially wind stress) and ocean state on the eastern equatorial Pacific SST variations are investigated using the Massachusetts Institute of Technology general circulation model (MITgcm) and its adjoint model, which can calculate the sensitivities of a cost function (in this case the averaged 0–30-m temperature in the Niño-3 region during an ENSO event peak) to previous atmospheric forcing fields and ocean state going backward in time. The sensitivity of the Niño-3 surface temperature to monthly zonal wind stress in preceding months can be understood by invoking mixed layer heat balance, ocean dynamics, and especially linear equatorial wave dynamics. The maximum positive sensitivity of the Niño-3 surface temperature to local wind forcing usually happens ~1–2 months before the peak of the ENSO event and is hypothesized to be associated with the Ekman pumping mechanism. In model experiments, its magnitude is closely related to the subsurface vertical temperature gradient, exhibiting strong event-to-event differences with strong (weak) positive sensitivity during La Niña (strong El Niño) events. The adjoint sensitivity to remote wind forcing in the central and western equatorial Pacific is consistent with the standard hypothesis that the remote wind forcing affects the Niño-3 surface temperature indirectly by exciting equatorial Kelvin and Rossby waves and modulating thermocline depth in the Niño-3 region. The current adjoint sensitivity study is consistent with a previous regression-based sensitivity study derived from perturbation experiments. Finally, implication for ENSO monitoring and prediction is also discussed.

scholarly journals Spatio-temporal structure of phytoplankton assemblages in the Eastern Equatorial Pacific in the El Niño Region 1+2

2016 ◽  
Vol 3 ◽  
Author(s):  
González-Narváez Mariela ◽  
Mendes Susana ◽  
Fernández-Gómez Mª José ◽  
Ruiz-Barzola Omar ◽  
Recalde Sonia ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Temporal Structure ◽  
Equatorial Pacific ◽  
Phytoplankton Assemblages ◽  
Eastern Equatorial Pacific ◽  
Spatio Temporal

scholarly journals On the Physics of the Warm Water Volume and El Niño/La Niña Predictability

2019 ◽  
Vol 49 (6) ◽  
pp. 1541-1560 ◽  
Author(s):  
Allan J. Clarke ◽  
Xiaolin Zhang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Pool ◽  
Equatorial Pacific ◽  
La Niña ◽  
Warm Water ◽  
Water Volume ◽  
La Nina ◽  
Eastern Equatorial Pacific ◽  
Warm Water Volume

AbstractPrevious work has shown that warm water volume (WWV), usually defined as the volume of equatorial Pacific warm water above the 20°C isotherm between 5°S and 5°N, leads El Niño. In contrast to previous discharge–recharge oscillator theory, here it is shown that anomalous zonal flow acceleration right at the equator and the movement of the equatorial warm pool are crucial to understanding WWV–El Niño dynamics and the ability of WWV to predict ENSO. Specifically, after westerly equatorial wind anomalies in a coupled ocean–atmosphere instability push the warm pool eastward during El Niño, the westerly anomalies follow the warmest water south of the equator in the Southern Hemisphere summer in December–February. With the wind forcing that causes El Niño in the eastern Pacific removed, the eastern equatorial Pacific sea level and thermocline anomalies decrease. Through long Rossby wave dynamics this decrease results in an anomalous westward equatorial flow that tends to push the warm pool westward and often results in the generation of a La Niña during March–June. The anomalously negative eastern equatorial Pacific sea level typically does not change as much during La Niña, the negative feedback is not as strong, and El Niños tend to not follow La Niñas the next year. This El Niño/La Niña asymmetry is seen in the WWV/El Niño phase diagram and decreased predictability during “La Niña–like” decades.

Sign in / Sign up

Export Citation Format

Share Document