On the Energy Exchange between Tropical Ocean Basins Related to ENSO*

2014 ◽  
Vol 27 (17) ◽  
pp. 6393-6403 ◽  
Author(s):  
Michael Mayer ◽  
Leopold Haimberger ◽  
Magdalena A. Balmaseda
Keyword(s):  
El Niño ◽  
Energy Transport ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Tropical Pacific ◽  
Surface Fluxes ◽  
Energy Budgets ◽  
Tropical Ocean ◽  
The Tropical Pacific

Abstract Vast amounts of energy are exchanged between the ocean, atmosphere, and space in association with El Niño–Southern Oscillation (ENSO). This study examines energy budgets of all tropical (30°S–30°N) ocean basins and the atmosphere separately using different, largely independent oceanic and atmospheric reanalyses to depict anomalous energy flows associated with ENSO in a consistent framework. It is found that variability of area-averaged ocean heat content (OHC) in the tropical Pacific to a large extent is modulated by energy flow through the ocean surface. While redistribution of OHC within the tropical Pacific is an integral part of ENSO dynamics, variability of ocean heat transport out of the tropical Pacific region is found to be mostly small. Noteworthy contributions arise from the Indonesian Throughflow (ITF), which is anticorrelated with ENSO at a few months lag, and from anomalous oceanic poleward heat export during the La Niña events in 1999 and 2008. Regression analysis reveals that atmospheric energy transport and radiation at the top of the atmosphere (RadTOA) almost perfectly balance the OHC changes and ITF variability associated with ENSO. Only a small fraction of El Niño–related heat lost by the Pacific Ocean through anomalous air–sea fluxes is radiated to space immediately, whereas the major part of the energy is transported away by the atmosphere. Ample changes in tropical atmospheric circulation lead to enhanced surface fluxes and, consequently, to an increase of OHC in the tropical Atlantic and Indian Ocean that almost fully compensates for tropical Pacific OHC loss. This signature of energy redistribution is robust across the employed datasets for all three tropical ocean basins and explains the small ENSO signal in global mean RadTOA.

scholarly journals Multiyear Statistical Prediction of ENSO Enhanced by the Tropical Pacific Observing System

2020 ◽  
Vol 33 (1) ◽  
pp. 163-174 ◽  
Author(s):  
Desislava Petrova ◽  
Joan Ballester ◽  
Siem Jan Koopman ◽  
Xavier Rodó
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Computational Cost ◽  
Tropical Pacific ◽  
Statistical Prediction ◽  
Tropical Ocean ◽  
Statistical Dynamic ◽  
Dynamic Components ◽  
The Tropical Pacific

AbstractThe theoretical predictability limit of El Niño–Southern Oscillation has been shown to be on the order of years, but long-lead predictions of El Niño (EN) and La Niña (LN) are still lacking. State-of-the-art forecasting schemes traditionally do not predict beyond the spring barrier. Recent efforts have been dedicated to the improvement of dynamical models, while statistical schemes still need to take full advantage of the availability of ocean subsurface variables, provided regularly for the last few decades as a result of the Tropical Ocean–Global Atmosphere Program (TOGA). Here we use a number of predictor variables, including temperature at different depths and regions of the equatorial ocean, in a flexible statistical dynamic components model to make skillful long-lead retrospective predictions (hindcasts) of the Niño-3.4 index in the period 1970–2016. The model hindcasts the major EN episodes up to 2.5 years in advance, including the recent extreme 2015/16 EN. The analysis demonstrates that events are predicted more accurately after the completion of the observational array in the tropical Pacific in 1994, as a result of the improved data quality and coverage achieved by TOGA. Therefore, there is potential to issue long-lead predictions of this climatic phenomenon at a low computational cost.

scholarly journals What Controls the Duration of El Niño and La Niña Events?

2019 ◽  
Vol 32 (18) ◽  
pp. 5941-5965 ◽  
Author(s):  
Xian Wu ◽  
Yuko M. Okumura ◽  
Pedro N. DiNezio
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Surface Wind ◽  
Heat Content ◽  
Tropical Pacific ◽  
La Niña ◽  
Tropical Atlantic ◽  
La Nina ◽  
The Tropical Pacific

Abstract The temporal evolution of El Niño and La Niña varies greatly from event to event. To understand the dynamical processes controlling the duration of El Niño and La Niña events, a suite of observational data and a long control simulation of the Community Earth System Model, version 1, are analyzed. Both observational and model analyses show that the duration of El Niño is strongly affected by the timing of onset. El Niño events that develop early tend to terminate quickly after the mature phase because of the early arrival of delayed negative oceanic feedback and fast adjustments of the tropical Atlantic and Indian Oceans to the tropical Pacific Ocean warming. The duration of La Niña events is, on the other hand, strongly influenced by the amplitude of preceding warm events. La Niña events preceded by a strong warm event tend to persist into the second year because of large initial discharge of the equatorial oceanic heat content and delayed adjustments of the tropical Atlantic and Indian Oceans to the tropical Pacific cooling. For both El Niño and La Niña, the interbasin sea surface temperature (SST) adjustments reduce the anomalous SST gradient toward the tropical Pacific and weaken surface wind anomalies over the western equatorial Pacific, hastening the event termination. Other factors external to the dynamics of El Niño–Southern Oscillation, such as coupled variability in the tropical Atlantic and Indian Oceans and atmospheric variability over the North Pacific, also contribute to the diversity of event duration.

scholarly journals Indian Ocean impact on ENSO evolution 2014–2016 in a set of seasonal forecasting experiments

2021 ◽  
Author(s):  
Michael Mayer ◽  
Magdalena Alonso Balmaseda
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
El Niño ◽  
Initial Conditions ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Tropical Pacific ◽  
Decadal Variations ◽  
The Indian Ocean

AbstractThis study investigates the influence of the anomalously warm Indian Ocean state on the unprecedentedly weak Indonesian Throughflow (ITF) and the unexpected evolution of El Niño-Southern Oscillation (ENSO) during 2014–2016. It uses 25-month-long coupled twin forecast experiments with modified Indian Ocean initial conditions sampling observed decadal variations. An unperturbed experiment initialized in Feb 2014 forecasts moderately warm ENSO conditions in year 1 and year 2 and an anomalously weak ITF throughout, which acts to keep tropical Pacific ocean heat content (OHC) anomalously high. Changing only the Indian Ocean to cooler 1997 conditions substantially alters the 2-year forecast of Tropical Pacific conditions. Differences include (i) increased probability of strong El Niño in 2014 and La Niña in 2015, (ii) significantly increased ITF transports and (iii), as a consequence, stronger Pacific ocean heat divergence and thus a reduction of Pacific OHC over the two years. The Indian Ocean’s impact in year 1 is via the atmospheric bridge arising from altered Indian Ocean Dipole conditions. Effects of altered ITF and associated ocean heat divergence (oceanic tunnel) become apparent by year 2, including modified ENSO probabilities and Tropical Pacific OHC. A mirrored twin experiment starting from unperturbed 1997 conditions and several sensitivity experiments corroborate these findings. This work demonstrates the importance of the Indian Ocean’s decadal variations on ENSO and highlights the previously underappreciated role of the oceanic tunnel. Results also indicate that, given the physical links between year-to-year ENSO variations, 2-year-long forecasts can provide additional guidance for interpretation of forecasted year-1 ENSO probabilities.

scholarly journals El Niño in a changing climate: a multi-model study

Ocean Science ◽  
2005 ◽  
Vol 1 (2) ◽  
pp. 81-95 ◽  
Author(s):  
G. J. van Oldenborgh ◽  
S. Y. Philip ◽  
M Collins
Keyword(s):  
Standard Deviation ◽  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Enso Cycle ◽  
Tropical Pacific Ocean ◽  
Enso Variability ◽  
The Tropical Pacific

Abstract. In many parts of the world, climate projections for the next century depend on potential changes in the properties of the El Niño - Southern Oscillation (ENSO). The current staus of these projections is assessed by examining a large set of climate model experiments prepared for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Firstly, the patterns and time series of present-day ENSO-like model variability in the tropical Pacific Ocean are compared with that observed. Next, the strength of the coupled atmosphere-ocean feedback loops responsible for generating the ENSO cycle in the models are evaluated. Finally, we consider the projections of the models with, what we consider to be, the most realistic ENSO variability. Two of the models considered do not have interannual variability in the tropical Pacific Ocean. Three models show a very regular ENSO cycle due to a strong local wind feedback in the central Pacific and weak sea surface temperature (SST) damping. Six other models have a higher frequency ENSO cycle than observed due to a weak east Pacific upwelling feedback loop. One model has much stronger upwelling feedback than observed, and another one cannot be described simply by the analysis technique. The remaining six models have a reasonable balance of feedback mechanisms and in four of these the interannual mode also resembles the observed ENSO both spatially and temporally. Over the period 2051-2100 (under various scenarios) the most realistic six models show either no change in the mean state or a slight shift towards El Niño-like conditions with an amplitude at most a quarter of the present day interannual standard deviation. We see no statistically significant changes in amplitude of ENSO variability in the future, with changes in the standard deviation of a Southern Oscillation Index that are no larger than observed decadal variations. Uncertainties in the skewness of the variability are too large to make any statements about the future relative strength of El Niño and La Niña events. Based on this analysis of the multi-model ensemble, we expect very little influence of global warming on ENSO.

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 Modulation of cross-isothermal velocities with ENSO in the tropical Pacific cold tongue

2021 ◽  
Author(s):  
Anna-Lena Deppenmeier ◽  
Frank O. Bryan ◽  
William Kessler ◽  
LuAnne Thompson
Keyword(s):  
El Niño ◽  
Cold Water ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Budget ◽  
Vertical Mixing ◽  
Tropical Pacific ◽  
Cold Tongue ◽  
Diabatic Processes ◽  
The Tropical Pacific

AbstractThe tropical Pacific cold tongue (CT) plays a major role in the global climate system. The strength of the CT sets the zonal temperature gradient in the Pacific that couples with the atmospheric Walker circulation. This coupling is an essential component of the El Niño Southern Oscillation (ENSO). The CT is supplied with cold water by the equatorial undercurrent that follows the thermocline as it shoals toward the east, adiabatically transporting cold water towards the surface. As the thermocline shoals, its water is transformed through diabatic processes producing water mass transformation (WMT) that allows water to cross mean isotherms. Here, we examine WMT in the cold tongue region from a global high resolution ocean simulation with saved budget terms that close its heat budget exactly. Using the terms of the heat budget, we quantify each individual component of WMT (vertical mixing, horizontal mixing, eddy fluxes, solar penetration), and find that vertical mixing is the single most important contribution in the thermocline, while solar heating dominates close to the surface. Horizontal diffusion is much smaller. During El Niño events, vertical mixing, and hence cross-isothermal flow as a whole, is much reduced, while during La Niña periods strong vertical mixing leads to strong WMT, thereby cooling the surface. This analysis demonstrates the enhancement of diabatic processes during cold events, which in turn enhances cooling of the CT from below the surface.

Diverse impacts of Indian Ocean Dipole on El Niño-Southern Oscillation

2021 ◽  
pp. 1-46
Author(s):  
Lei Zhang ◽  
Weiqing Han ◽  
Gerald A. Meehl ◽  
Aixue Hu ◽  
Nan Rosenbloom ◽  
...  
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
The Impact ◽  
The Tropical Pacific

AbstractUnderstanding the impact of the Indian Ocean Dipole (IOD) on El Niño-Southern Oscillation (ENSO) is important for climate prediction. By analyzing observational data and performing Indian and Pacific Ocean pacemaker experiments using a state-of-the-art climate model, we find that a positive IOD (pIOD) can favor both cold and warm sea surface temperature anomalies (SSTA) in the tropical Pacific, in contrast to the previously identified pIOD-El Niño connection. The diverse impacts of the pIOD on ENSO are related to SSTA in the Seychelles-Chagos thermocline ridge (SCTR; 60°E-85°E and 7°S-15°S) as part of the warm pole of the pIOD. Specifically, a pIOD with SCTR warming can cause warm SSTA in the southeast Indian Ocean, which induces La Niña-like conditions in the tropical Pacific through interbasin interaction processes associated with a recently identified climate phenomenon dubbed the “Warm Pool Dipole”. This study identifies a new pIOD-ENSO relationship and examines the associated mechanisms.

Impacts of El Niño-Southern Oscillation on Natural and Human Systems

2007 ◽  
Author(s):  
César N. Caviedes
Keyword(s):  
El Niño ◽  
Wind Shear ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Tropical Species ◽  
Humboldt Current ◽  
The Pacific ◽  
Gulf Of Guayaquil ◽  
The Tropical Pacific

Off the coasts of northern Perú and southern Ecuador, warm equatorial waters meet the cold Humboldt Current. Variations in sea temperatures and associated fauna have been known to fishing folk since colonial times. They noticed that toward the end of every year tepid waters appeared between the Gulf of Guayaquil (Ecuador) and Point Pariñas (Perú) and persisted until late February, causing tropical species to be added to the fish they commonly caught. Coupled with the arrival of warm waters was a surge in air humidity and an increase in summer showers. Since this environmental phenomenon occurred around Christmas, the local fishermen called it El Niño, or Child Jesus. Early scientific observations on the nature and extent of these phenomena revealed that they were not regionally restricted to coastal Perú and Ecuador, but extended over the whole tropical Pacific, involving pressure fields and wind flows across the basin. Thus, when referring to this coupled ocean-atmospheric system, both variations of sea temperature across the tropical Pacific and changes of the atmosphere in contact with the ocean must be considered (Neelin et al., 1998). Normally, the tropical Pacific Ocean, from the coast of Ecuador and Perú to longitude 120°W, is dominated by westward- flowing cold waters, which are the prolongation of the Humboldt Current. Near longitude 120°W, sea surface temperatures approach normal equatorial values of ~28°C. When the flow reaches the western Pacific, it creates a sealevel rise of nearly 40 cm, which is maintained by the wind shear of the equatorial easterlies. The thermocline, which marks the lower boundary of the sun-heated water layer, runs at a depth of 40 m between Perú and the Galápagos Islands, but on the Asian side of the Pacific it dips to 120 m, revealing a marked asymmetry in the thickness of the sunheated layer across the Pacific. During El Niño years, the westward flow of cooler waters is weak because there is less wind shear from the easterly winds, and the thermocline plunges to 80 m in the eastern equatorial Pacific.

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