scholarly journals The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event

2016 ◽  
Vol 29 (16) ◽  
pp. 5859-5877 ◽  
Author(s):  
Han-Ching Chen ◽  
Zeng-Zhen Hu ◽  
Bohua Huang ◽  
Chung-Hsiung Sui
Keyword(s):  
El Niño ◽  
El Nino ◽  
Equatorial Pacific ◽  
La Niña ◽  
Eastern Pacific ◽  
Enso Events ◽  
Mature Phase ◽  
La Nina ◽  
Eastern Equatorial Pacific ◽  
Equatorial Thermocline

Abstract This study shows the sudden basinwide reversal of anomalous equatorial zonal transport above the thermocline at the peaking phase of ENSO triggers rapid termination of ENSO events. The anomalous equatorial zonal transport is controlled by the concavity of anomalous thermocline meridional structure across the equator. During the developing phase of ENSO, opposite zonal transport anomalies form in the western-central and central-eastern equatorial Pacific, respectively. Both are driven by the equatorial thermocline anomalies in response to zonal wind anomalies over the western-central equatorial ocean. At this stage, the anomalous zonal transport in the east enhances ENSO growth through zonal SST advection. In the mature phase of ENSO, off-equatorial thermocline depth anomalies become more dominant in the eastern Pacific because of the reflection of equatorial signals at the eastern boundary. As a result, the meridional concavity of the thermocline anomalies is reversed in the east. This change reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, joining with the existing reversed zonal transport anomalies farther to the west, and forms a basinwide transport reversal throughout the equatorial Pacific. This basinwide transport reversal weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal transport reduces the existing zonal tilting of the equatorial thermocline and weakens its feedback to wind anomalies effectively. This basinwide reversal is built in at the peak phase of ENSO as an oceanic control on the evolution of both El Niño and La Niña events. The reversed zonal transport anomaly after the mature phase weakens El Niño in the eastern Pacific more efficiently than it weakens La Niña.

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.

scholarly journals Different influencing mechanisms of two ENSO types on the interannual variation in diurnal SST over the Niño 3 and 4 regions

2021 ◽  
pp. 1-47
Author(s):  
XIAODAN YANG ◽  
YAJUAN SONG ◽  
MENG WEI ◽  
YUHUAN XUE ◽  
ZHENYA SONG
Keyword(s):  
El Niño ◽  
Interannual Variation ◽  
El Nino ◽  
Southern Oscillation ◽  
Equatorial Pacific ◽  
La Niña ◽  
Trade Wind ◽  
Enso Events ◽  
Cp El Niño ◽  
La Nina

AbstractIn this paper, the different effects of the eastern equatorial Pacific (EP) and central equatorial Pacific (CP) El Niño-Southern Oscillation (ENSO) events on interannual variation in the diurnal sea surface temperature (SST) are explored in both the Niño 3 and Niño 4 regions. In the Niño 3 region, the diurnal SST anomaly (DSSTA) is negative during both EP and CP El Niño events and becomes positive during both EP and CP La Niña events. However, the DSSTA in the Niño 4 region is positive in El Niño years and negative in La Niña years, which is opposite to that in the Niño 3 region. Further analysis indicates that the incident shortwave radiation (SWR), wind stress (WS), and upward latent heat flux (LHF) are the main factors causing the interannual variation in the DSST. In the Niño 3 region, the decreased/increased SWR and the increased (decreased) LHF lead to the negative (positive) DSSTA in EP El Niño (La Niña) years. In addition, the enhanced (reduced) WS and the increased (decreased) LHF cause the negative (positive) DSSTA in CP El Niño (La Niña) years. In the Niño 4 region, the reduced (enhanced) trade wind plays a key role in producing in the positive (negative) DSSTA, while the decreased (increased) SWR has an opposite effect that reduces/increases the range of the DSSTA during both EP and CP El Niño (La Niña) events.

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.

scholarly journals Dynamics for El Niño-La Niña asymmetry constrain equatorial-Pacific warming pattern

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Michiya Hayashi ◽  
Fei-Fei Jin ◽  
Malte F. Stuecker
Keyword(s):  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Southern Oscillation ◽  
Equatorial Pacific ◽  
La Niña ◽  
Nonlinear Dynamical ◽  
La Nina ◽  
Warming Pattern ◽  
Enso Asymmetry

Abstract The El Niño-Southern Oscillation (ENSO) results from the instability of and also modulates the strength of the tropical-Pacific cold tongue. While climate models reproduce observed ENSO amplitude relatively well, the majority still simulates its asymmetry between warm (El Niño) and cold (La Niña) phases very poorly. The causes of this major deficiency and consequences thereof are so far not well understood. Analysing both reanalyses and climate models, we here show that simulated ENSO asymmetry is largely proportional to subsurface nonlinear dynamical heating (NDH) along the equatorial Pacific thermocline. Most climate models suffer from too-weak NDH and too-weak linear dynamical ocean-atmosphere coupling. Nevertheless, a sizeable subset (about 1/3) having relatively realistic NDH shows that El Niño-likeness of the equatorial-Pacific warming pattern is linearly related to ENSO amplitude change in response to greenhouse warming. Therefore, better simulating the dynamics of ENSO asymmetry potentially reduces uncertainty in future projections.

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.

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