scholarly journals A review of ENSO theories

2018 ◽  
Vol 5 (6) ◽  
pp. 813-825 ◽  
Author(s):  
Chunzai Wang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Enso Event ◽  
Tropical Pacific ◽  
Kelvin Waves ◽  
Western Pacific ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Negative Feedbacks ◽  
The Tropical Pacific

Abstract The El Niño and the Southern Oscillation (ENSO) occurrence can be usually explained by two views of (i) a self-sustained oscillatory mode and (ii) a stable mode interacting with high-frequency forcing such as westerly wind bursts and Madden-Julian Oscillation events. The positive ocean–atmosphere feedback in the tropical Pacific hypothesized by Bjerknes leads the ENSO event to a mature phase. After ENSO event matures, negative feedbacks are needed to cease the ENSO anomaly growth. Four negative feedbacks have been proposed: (i) reflected Kelvin waves at the ocean western boundary, (ii) a discharge process due to Sverdrup transport, (iii) western-Pacific wind-forced Kelvin waves and (iv) anomalous zonal advections and wave reflection at the ocean eastern boundary. These four ENSO mechanisms are respectively called the delayed oscillator, the recharge–discharge oscillator, the western-Pacific oscillator and the advective–reflective oscillator. The unified oscillator is developed by including all ENSO mechanisms, i.e. all four ENSO oscillators are special cases of the unified oscillator. The tropical Pacific Ocean and atmosphere interaction can also induce coupled slow westward- and eastward-propagating modes. An advantage of the coupled slow modes is that they can be used to explain the propagating property of interannual anomalies, whereas the oscillatory modes produce a standing oscillation. The research community has recently paid attention to different types of ENSO events by focusing on the central-Pacific El Niño. All of the ENSO mechanisms may work for the central-Pacific El Niño events, with an addition that the central-Pacific El Niño may be related to forcing or processes in the extra-tropical Pacific.

A decadal tropical Pacific condition unfavorable to central Pacific El Niño

2017 ◽  
Vol 44 (15) ◽  
pp. 7919-7926 ◽  
Author(s):  
Wenxiu Zhong ◽  
Xiao-Tong Zheng ◽  
Wenju Cai
Keyword(s):  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Central Pacific ◽  
Central Pacific El Niño

scholarly journals Impact of westerly wind burst on El Niño-sourthern oscillation

2020 ◽  
Author(s):  
◽  
Mohammad Alam
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Vital Role ◽  
Tropical Pacific ◽  
Westerly Wind ◽  
Central Pacific ◽  
Enso Events ◽  
The Tropical Pacific

Westerly wind bursts (WWBs), usually occurring in the tropical Pacific region, play a vital role in El Niño–Southern Oscillation (ENSO). In this study, we use a hybrid coupled model (HCM) for the tropical Pacific Ocean-atmosphere system to investigate WWBs impact on ENSO. To achieve this goal, two experiments are performed: (a) first, the standard version of the HCM is integrated for years without prescribed WWBs events; and (b) second, the WWBs are added into the HCM (HCM-WWBs). Results show that HCM-WWBs can generate not only more realistic climatology of sea surface temperature (SST) in both spatial structure and temporal amplitudes, but also better ENSO features, than the HCM. In particular, the HCM-WWBs can capture the central Pacific (CP) ENSO events, which is absent in original HCM. Furthermore, the possible physical mechanisms responsible for these improvements by WWBs are discussed.

scholarly journals Ocean salinity indices of interannual modes in the tropical Pacific

2021 ◽  
Author(s):  
Jianwei Chi ◽  
Tangdong Qu ◽  
Yan Du ◽  
Jifeng Qi ◽  
Ping Shi
Keyword(s):  
Global Warming ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Eastern Pacific ◽  
Dipole Mode ◽  
Eastern Tropical Pacific ◽  
Central Pacific El Niño ◽  
Eastern Pacific El Niño ◽  
The Tropical Pacific

AbstractThis study investigates the interannual modes of the tropical Pacific using salinity from observations, ocean reanalysis output and CMIP6 products. Here we propose two indices of sea surface salinity (SSS), a monopole mode and a dipole mode, to identify the El Niño—South Oscillation (ENSO) and its diversity, respectively. The monopole mode is primarily controlled by atmospheric forcing, namely, the enhanced precipitation that induces negative SSS anomalies across nearly the entire tropical Pacific. The dipole mode is mainly forced by oceanic dynamics, with zonal current transporting fresh water from the western fresh pool into the western-central and salty water from the subtropics into the eastern tropical Pacific. Under a global warming condition, an increase in the monopole and dipole mode variance indicates an increase in both the central and eastern Pacific El Niño variability. The increase in central Pacific El Niño variability is largely due to enhanced vertical stratification during global warming in the upper layer, with intensified zonal advection. An eastern Pacific El Niño-like warming pattern contributes to the increase in eastern Pacific El Niño, with enhanced precipitation over the central-eastern tropical Pacific.

scholarly journals A Precursory Signal of the Central Pacific El Niño Event: Eastern Pacific Cooling Mode

2021 ◽  
Author(s):  
Tao Lingjiang ◽  
Duan Wansuo
Keyword(s):  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Cooling Mode ◽  
Central Pacific El Niño ◽  
Climate Effect ◽  
Cp El Niño ◽  
El Niño Event ◽  
Basin Scale ◽  
The Tropical Pacific

Abstract In recent decades, the tropical Pacific frequently experiences a new type of El Niño with warming center in the central tropical Pacific (i.e., the CP-El Niño) with distinct global climate effect to the traditional El Niño (i.e., EP-El Niño). Predicting the El Niño diversity is still a huge challenge for climatologists partly due to the precursory signals of El Niño events with different type is unclear. In the present study, a novel precursory signal that presents a negative sea surface temperature anomaly in the eastern tropical Pacific (i.e., EP-cooling mode) is revealed, which tends to evolve into a CP-El Niño event. The transition from the EP-cooling mode to CP-El Niño is explained by the basin-scale air-sea coupling in the tropical Pacific and teleconnections between the tropical and North Pacific. With the EP-cooling mode as a predictor, the forecast skill for the CP-El Niño in hindcast experiments is obviously improved by using regression models. The results in the present study are therefore instructive for promoting a better understanding of El Niño diversity and predictability.

scholarly journals A Review of Atmosphere–Ocean Forcings Outside the Tropical Pacific on the El Niño–Southern Oscillation Occurrence

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 439 ◽  
Author(s):  
Shangfeng Chen ◽  
Bin Yu ◽  
Wen Chen ◽  
Renguang Wu
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Western Pacific ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Enso Variability ◽  
Tropical Western Pacific ◽  
The Tropical Pacific

The El Niño–Southern Oscillation (ENSO) is the strongest interannual air–sea coupled variability mode in the tropics, and substantially impacts the global weather and climate. Hence, it is important to improve our understanding of the ENSO variability. Besides the well-known air–sea interaction process over the tropical Pacific, recent studies indicated that atmospheric and oceanic forcings outside the tropical Pacific also play important roles in impacting and modulating the ENSO occurrence. This paper reviews the impacts of the atmosphere–ocean variability outside the tropical Pacific on the ENSO variability, as well as their associated physical processes. The review begins with the contribution of the atmosphere–ocean forcings over the extratropical North Pacific, Atlantic, and Indian Ocean on the ENSO occurrence. Then, an overview of the extratropical atmospheric forcings over the Northern Hemisphere (including the Arctic Oscillation and the Asian monsoon systems) and the Southern Hemisphere (including the Antarctic Oscillation and the Pacific–South American teleconnection), on the ENSO occurrence, is presented. It is shown that the westerly (easterly) wind anomaly over the tropical western Pacific is essential for the occurrence of an El Niño (a La Niña) event. The wind anomalies over the tropical western Pacific also play a key role in relaying the impacts of the atmosphere–ocean forcings outside the tropical Pacific on the ENSO variability. Finally, some relevant questions, that remain to be explored, are discussed.

scholarly journals An Investigation of the Differences between the North American Dipole and North Atlantic Oscillation

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 58 ◽  
Author(s):  
Xuejing Zhou ◽  
Wei Wang ◽  
Ruiqiang Ding ◽  
Jianping Li ◽  
Zhaolu Hou ◽  
...  
Keyword(s):  
North Atlantic ◽  
North American ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Central Pacific ◽  
The North ◽  
El Niño Event ◽  
Sst Warming ◽  
The Tropical Pacific

This study examines the differences between the North American dipole (NAD) and the North American Oscillation (NAO) in terms of their spatial structure, temporal variations, and climate impacts. The results indicate that the sea level pressure anomalies associated with the NAD are located in more western and southern areas than those associated with the NAO, and that the NAD has its own temporal variability. In addition, the NAD has a greater influence on sea surface temperature (SST) and precipitation anomalies in the northern tropical Atlantic (NTA) than the NAO does in the North Atlantic. In the tropical Pacific, the NAD tends to be more effective in forcing SST warming during spring in the northeastern subtropical Pacific (NESP). This can extend equatorward to reach the equatorial central Pacific in the autumn, finally leading to a central Pacific (CP)-type El Niño event. In contrast, the NAO induces only weak SST warming over the NESP, so that a CP-type El Niño event does not occur. Additional analysis indicates that the influence of the NAO can pass to the tropical Pacific only when the NAD and NAO have the same sign, suggesting that the NAD may serve as an important bridge linking the NAO to El Niño–Southern Oscillation (ENSO).

Salinity variability in the tropical Pacific during the Central-Pacific and Eastern-Pacific El Niño events

2019 ◽  
Vol 199 ◽  
pp. 103225 ◽  
Author(s):  
Jifeng Qi ◽  
Linlin Zhang ◽  
Tangdong Qu ◽  
Baoshu Yin ◽  
Zhenhua Xu ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Eastern Pacific El Niño ◽  
Salinity Variability ◽  
El Niño Events ◽  
El Nino Events ◽  
The Tropical Pacific

scholarly journals Changes in Independency between Two Types of El Niño Events under a Greenhouse Warming Scenario in CMIP5 Models

2015 ◽  
Vol 28 (19) ◽  
pp. 7561-7575 ◽  
Author(s):  
Yoo-Geun Ham ◽  
Yerim Jeong ◽  
Jong-Seong Kug
Keyword(s):  
Global Warming ◽  
El Niño ◽  
El Nino ◽  
Western Pacific ◽  
Cmip5 Models ◽  
Greenhouse Warming ◽  
Central Pacific ◽  
El Niño Events ◽  
The Western Pacific ◽  
El Nino Events

Abstract This study uses archives from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to investigate changes in independency between two types of El Niño events caused by greenhouse warming. In the observations, the independency between cold tongue (CT) and warm pool (WP) El Niño events is distinctively increased in recent decades. The simulated changes in independency between the two types of El Niño events according to the CMIP5 models are quite diverse, although the observed features are simulated to some extent in several climate models. It is found that the climatological change after global warming is an essential factor in determining the changes in independency between the two types of El Niño events. For example, the independency between these events is increased after global warming when the climatological precipitation is increased mainly over the equatorial central Pacific. This climatological precipitation increase extends convective response to the east, particularly for CT El Niño events, which leads to greater differences in the spatial pattern between the two types of El Niño events to increase the El Niño independency. On the contrary, in models with decreased independency between the two types of El Niño events after global warming, climatological precipitation is increased mostly over the western Pacific. This confines the atmospheric response to the western Pacific in both El Niño events; therefore, the similarity between them is increased after global warming. In addition to the changes in the climatological state after global warming, a possible connection of the changes in the El Niño independency with the historical mean state is discussed in this paper.

scholarly journals Two-year consecutive concurrences of positive Indian Ocean Dipole and Central Pacific El Niño preconditioned the 2019/2020 Australian “black summer” bushfires

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Guojian Wang ◽  
Wenju Cai
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Greenhouse Warming ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Positive Indian Ocean Dipole ◽  
The Future ◽  
Rainfall Anomalies

Abstract The 2019/20 Australian black summer bushfires were particularly severe in many respects, including its early commencement, large spatial coverage, and large number of burning days, preceded by record dry and hot anomalies. Determining whether greenhouse warming has played a role is an important issue. Here, we examine known modes of tropical climate variability that contribute to droughts in Australia to provide a gauge. We find that a two-year consecutive concurrence of the 2018 and 2019 positive Indian Ocean Dipole and the 2018 and 2019 Central Pacific El Niño, with the former affecting Southeast Australia, and the latter influencing eastern and northeastern Australia, may explain many characteristics of the fires. Such consecutive events occurred only once in the observations since 1911. Using two generations of state-of-the-art climate models under historical and a business-as-usual emission scenario, we show that the frequency of such consecutive concurrences increases slightly, but rainfall anomalies during such events are stronger in the future climate, and there are drying trends across Australia. The impact of the stronger rainfall anomalies during such events under drying trends is likely to be exacerbated by greenhouse warming-induced rise in temperatures, making such events in the future even more extreme.

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