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 Switch Between El Nino and La Nina is Caused by Subsurface Ocean Waves Likely Driven by Lunar Tidal Forcing

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jialin Lin ◽  
Taotao Qian
Keyword(s):  
El Niño ◽  
El Nino ◽  
Ocean Waves ◽  
La Niña ◽  
Slow Phase ◽  
Enso Events ◽  
The Past ◽  
La Nina ◽  
Subsurface Ocean ◽  
Sst Anomaly

Abstract The El Nino-Southern Oscillation (ENSO) is the dominant interannual variability of Earth’s climate system, and strongly modulates global temperature, precipitation, atmospheric circulation, tropical cyclones and other extreme events. However, forecasting ENSO is one of the most difficult problems in climate sciences affecting both interannual climate prediction and decadal prediction of near-term global climate change. The key question is what cause the switch between El Nino and La Nina. For the past 30 years, ENSO forecasts have been limited to short lead times after ENSO sea surface temperature (SST) anomaly has already developed, but unable to predict the switch between El Nino and La Nina. Here, we demonstrate that the switch between El Nino and La Nina is caused by a subsurface ocean wave propagating from western Pacific to central and eastern Pacific and then triggering development of SST anomaly. This is based on analysis of all ENSO events in the past 136 years using multiple long-term observational datasets. The wave’s slow phase speed and decoupling from atmosphere indicate that it is a forced wave. Further analysis of Earth’s angular momentum budget and NASA’s Apollo Landing Mirror Experiment suggests that the subsurface wave is likely driven by lunar tidal gravitational force.

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.

Model Biases in the Simulation of the Springtime North Pacific ENSO Teleconnection

2020 ◽  
Vol 33 (23) ◽  
pp. 9985-10002
Author(s):  
Ruyan Chen ◽  
Isla R. Simpson ◽  
Clara Deser ◽  
Bin Wang
Keyword(s):  
El Niño ◽  
North Pacific ◽  
Climate Models ◽  
El Nino ◽  
Coupled Model ◽  
La Niña ◽  
Late Winter ◽  
The North ◽  
La Nina ◽  
The North Pacific

AbstractThe wintertime ENSO teleconnection over the North Pacific region consists of an intensified (weakened) low pressure center during El Niño (La Niña) events both in observations and in climate models. Here, it is demonstrated that this teleconnection persists too strongly into late winter and spring in the Community Earth System Model (CESM). This discrepancy arises in both fully coupled and atmosphere-only configurations, when observed SSTs are specified, and is shown to be robust when accounting for the sampling uncertainty due to internal variability. Furthermore, a similar problem is found in many other models from piControl simulations of the Coupled Model Intercomparison Project (23 out of 43 in phase 5 and 11 out of 20 in phase 6). The implications of this bias for the simulation of surface climate anomalies over North America are assessed. The overall effect on the ENSO composite field (El Niño minus La Niña) resembles an overly prolonged influence of ENSO into the spring with anomalously high temperatures over Alaska and western Canada, and wet (dry) biases over California (southwest Canada). Further studies are still needed to disentangle the relative roles played by diabatic heating, background flow, and other possible contributions in determining the overly strong springtime ENSO teleconnection intensity over the North Pacific.

Composite Analysis of the Effects of ENSO Events on Antarctica

2016 ◽  
Vol 29 (5) ◽  
pp. 1797-1808 ◽  
Author(s):  
Lee J. Welhouse ◽  
Matthew A. Lazzara ◽  
Linda M. Keller ◽  
Gregory J. Tripoli ◽  
Matthew H. Hitchman
Keyword(s):  
El Niño ◽  
Geopotential Height ◽  
El Nino ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
La Niña ◽  
Austral Spring ◽  
Enso Events ◽  
La Nina ◽  
The Relationship

Abstract Previous investigations of the relationship between El Niño–Southern Oscillation (ENSO) and the Antarctic climate have focused on regions that are impacted by both El Niño and La Niña, which favors analysis over the Amundsen and Bellingshausen Seas (ABS). Here, 35 yr (1979–2013) of European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) data are analyzed to investigate the relationship between ENSO and Antarctica for each season using a compositing method that includes nine El Niño and nine La Niña periods. Composites of 2-m temperature (T2m), sea level pressure (SLP), 500-hPa geopotential height, sea surface temperatures (SST), and 300-hPa geopotential height anomalies were calculated separately for El Niño minus neutral and La Niña minus neutral conditions, to provide an analysis of features associated with each phase of ENSO. These anomaly patterns can differ in important ways from El Niño minus La Niña composites, which may be expected from the geographical shift in tropical deep convection and associated pattern of planetary wave propagation into the Southern Hemisphere. The primary new result is the robust signal, during La Niña, of cooling over East Antarctica. This cooling is found from December to August. The link between the southern annular mode (SAM) and this cooling is explored. Both El Niño and La Niña experience the weakest signal during austral autumn. The peak signal for La Niña occurs during austral summer, while El Niño is found to peak during austral spring.

scholarly journals Reversed Spatial Asymmetries between El Niño and La Niña and Their Linkage to Decadal ENSO Modulation in CMIP3 Models

2011 ◽  
Vol 24 (20) ◽  
pp. 5423-5434 ◽  
Author(s):  
Jin-Yi Yu ◽  
Seon Tae Kim
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Interaction Mechanism ◽  
Tropical Pacific ◽  
La Niña ◽  
Enso Events ◽  
La Nina ◽  
Spatial Asymmetries ◽  
Mean State

Abstract This study examines preindustrial simulations from Coupled Model Intercomparison Project, phase 3 (CMIP3), models to show that a tendency exists for El Niño sea surface temperature anomalies to be located farther eastward than La Niña anomalies during strong El Niño–Southern Oscillation (ENSO) events but farther westward than La Niña anomalies during weak ENSO events. Such reversed spatial asymmetries are shown to force a slow change in the tropical Pacific Ocean mean state that in return modulates ENSO amplitude. CMIP3 models that produce strong reversed asymmetries experience cyclic modulations of ENSO intensity, in which strong and weak events occur during opposite phases of a decadal variability mode associated with the residual effects of the reversed asymmetries. It is concluded that the reversed spatial asymmetries enable an ENSO–tropical Pacific mean state interaction mechanism that gives rise to a decadal modulation of ENSO intensity and that at least three CMIP3 models realistically simulate this interaction mechanism.

scholarly journals PDO–ENSO Effects in the Climate of Mexico

2006 ◽  
Vol 19 (24) ◽  
pp. 6433-6438 ◽  
Author(s):  
Edgar G. Pavia ◽  
Federico Graef ◽  
Jorge Reyes
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Climate Anomalies ◽  
Enso Events ◽  
La Nina ◽  
Mean Temperature ◽  
The Pacific

Abstract The role of the Pacific decadal oscillation (PDO) in El Niño–Southern Oscillation (ENSO)-related Mexican climate anomalies during winter and summer is investigated. The precipitation and mean temperature data of approximately 1000 stations throughout Mexico are considered. After sorting ENSO events by warm phase (El Niño) and cold phase (La Niña) and prevailing PDO phase: warm or high (HiPDO) and cold or low (LoPDO), the authors found the following: 1) For precipitation, El Niño favors wet conditions during summers of LoPDO and during winters of HiPDO. 2) For mean temperature, cooler conditions are favored during La Niña summers and during El Niño winters, regardless of the PDO phase; however, warmer conditions are favored by the HiPDO during El Niño summers.

scholarly journals Spatial Analysis of the Yellowfin Tuna (Thunnus albacares) Fishery, and its Relation to El Niño and La Niña Events in the Tropical Eastern Pacific

2002 ◽  
Vol 30 (1) ◽  
Author(s):  
Juan Antonio de Anda-Montañez ◽  
Susana Martínez-Aguilar ◽  
Alberto Amador-Buenrostro ◽  
Adriana Muhlia-Almazán
Keyword(s):  
Spatial Analysis ◽  
El Niño ◽  
El Nino ◽  
Yellowfin Tuna ◽  
La Niña ◽  
Eastern Pacific ◽  
Thunnus Albacares ◽  
Tropical Eastern Pacific ◽  
La Nina

scholarly journals The Pause End and Major Temperature Impacts during Super El Niños are Due to Shortwave Radiation Anomalies

2020 ◽  
pp. 1-20
Author(s):  
Antero Ollila
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
La Niña ◽  
Global Temperature ◽  
Temperature Changes ◽  
Simple Climate Model ◽  
Enso Events ◽  
La Nina ◽  
Temperature Impacts

The hiatus or temperature pause during the 21st century has been the subject of numerous research studies with very different results and proposals. In this study, two simple climate models have been applied to test the causes of global temperature changes. The climate change factors have been shortwave (SW) radiation changes, changes in cloudiness and ENSO (El Niño Southern Oscillation) events assessed as the ONI (Oceanic Niño Index) values and anthropogenic climate drivers. The results show that a simple climate model assuming no positive water feedback follows the satellite temperature changes very well, the mean absolute error (MAE) during the period from 2001 to July 2019 being 0.073°C and 0.082°C in respect to GISTEMP. The IPCC’s simple climate model shows for the same period errors of 0.191°C and 0.128°C respectively. The temperature in 2017-2018 was about 0.2°C above the average value in 2002–2014. The conclusion is that the pause was over after 2014 and the SW anomaly forcing was the major reason for this temperature increase. SW anomalies have had their greatest impacts on the global temperature during very strong (super) El Niño events in 1997-98 and 2015-16, providing a new perspective for ENSO events. A positive SW anomaly continued after 2015-16 which may explain the weak La Niña 2016 temperature impacts, and a negative SW anomaly after 1997-98 may have contributed two strong La Niña peaks 1998-2001. No cause and effect connection could be found between the SW radiation and temperature anomalies in Nino areas.

Impacts of El Niño and La Niña Cycles: Systems and Sectors

2008 ◽  
Author(s):  
Cynthia Rosenzweig ◽  
Daniel Hillel
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
La Niña ◽  
Enso Events ◽  
La Nina ◽  
The Pacific ◽  
The Pacific Ocean

Perturbations of the climate system caused by El Niño and La Niña events affect natural and managed systems in vast areas of the Pacific Ocean and far beyond it. (Other oscillations affect systems and sectors in wide swaths of the world as well.)1 El Niño–Southern Oscillation (ENSO) events have been associated with ecosystem disruptions and forest fires, crop failures and famines, disease epidemics, and even market fluctuations in various regions. The forms and degrees of impact depend not only on the strength and duration of an El Niño or La Niña event and its associated teleconnections, but also on the state, sensitivity, and vulnerability of the affected system and its biotic community, as well as its human population. The underlying characteristics of ecosystems and human societies in each region are important factors in their susceptibility to ENSO-related damages. Variation may be enhanced as ENSO effects ripple through natural and managed ecosystems. The underlying health of the affected biota, interrelationships among different biotic associations, and pressure by humans all affect marine as well as terrestrial ecosystem responses to ENSO events. Impacts on human systems can be both direct and indirect. Some ENSO phenomena, such as severe storms, affect human lives and infrastructures directly. Other impacts occur through alterations in the marine and terrestrial ecosystems and water supplies upon which human populations ultimately depend. In this chapter we consider some of the impacts that ENSO and other oscillations (described with their teleconnections in chapter 1) have on marine and terrestrial ecosystems and on human-managed systems apart from agriculture. The significant and geographically widespread changes that El Niño events induce in the Pacific Ocean alter conditions for various marine communities. These alterations include dramatic changes in the abundance and distribution of organisms, associated collapses of commercial fisheries, and ensuing consequences affecting human livelihood (Glantz, 2004; Lehodey et al., 2006). Some of the effects are well documented. Reductions in primary production of up to 95% were measured in the eastern equatorial Pacific in 1982–83 (Barber and Chavez, 1983.) Large changes in ecosystem structure and productivity have also been recorded in other parts of the Pacific Ocean, including the western Pacific and in the North Pacific subtropical gyre (north of the Hawaiian Islands) (Karl et al., 1995).

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