scholarly journals Links between Tropical Pacific SST and Cholera Incidence in Bangladesh: Role of the Eastern and Central Tropical Pacific

2008 ◽  
Vol 21 (18) ◽  
pp. 4647-4663 ◽  
Author(s):  
Benjamin A. Cash ◽  
Xavier Rodó ◽  
James L. Kinter
Keyword(s):  
El Niño ◽  
General Circulation ◽  
Physical Mechanism ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Circulation Model ◽  
Tropical Pacific ◽  
Bacterial Disease ◽  
Monsoon Circulation

Abstract Recent studies arising from both statistical analysis and dynamical disease models indicate that there is a link between incidence of cholera, a paradigmatic waterborne bacterial disease (WBD) endemic to Bangladesh, and the El Niño–Southern Oscillation (ENSO). However, a physical mechanism explaining this relationship has not yet been established. A regionally coupled, or “pacemaker,” configuration of the Center for Ocean–Land–Atmosphere Studies atmospheric general circulation model is used to investigate links between sea surface temperature in the central and eastern tropical Pacific and the regional climate of Bangladesh. It is found that enhanced precipitation tends to follow winter El Niño events in both the model and observations, providing a plausible physical mechanism by which ENSO could influence cholera in Bangladesh. The enhanced precipitation in the model arises from a modification of the summer monsoon circulation over India and Bangladesh. Westerly wind anomalies over land to the west of Bangladesh lead to increased convergence in the zonal wind field and hence increased moisture convergence and rainfall. This change in circulation results from the tropics-wide warming in the model following a winter El Niño event. These results suggest that improved forecasting of cholera incidence may be possible through the use of climate predictions.

scholarly journals Indo-Western Pacific Climate Variability: ENSO Forcing and Internal Dynamics in a Tropical Pacific Pacemaker Simulation

2018 ◽  
Vol 31 (24) ◽  
pp. 10123-10139 ◽  
Author(s):  
Chuan-Yang Wang ◽  
Shang-Ping Xie ◽  
Yu Kosaka
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Internal Variability ◽  
Tropical Pacific ◽  
Western Pacific ◽  
Ocean Atmosphere ◽  
Sst Anomalies

El Niño–Southern Oscillation (ENSO) peaks in boreal winter but its impact on Indo-western Pacific climate persists for another two seasons. Key ocean–atmosphere interaction processes for the ENSO effect are investigated using the Pacific Ocean–Global Atmosphere (POGA) experiment with a coupled general circulation model, where tropical Pacific sea surface temperature (SST) anomalies are restored to follow observations while the atmosphere and oceans are fully coupled elsewhere. The POGA shows skills in simulating the ENSO-forced warming of the tropical Indian Ocean and an anomalous anticyclonic circulation pattern over the northwestern tropical Pacific in the post–El Niño spring and summer. The 10-member POGA ensemble allows decomposing Indo-western Pacific variability into the ENSO forced and ENSO-unrelated (internal) components. Internal variability is comparable to the ENSO forcing in magnitude and independent of ENSO amplitude and phase. Random internal variability causes apparent decadal modulations of ENSO correlations over the Indo-western Pacific, which are high during epochs of high ENSO variance. This is broadly consistent with instrumental observations over the past 130 years as documented in recent studies. Internal variability features a sea level pressure pattern that extends into the north Indian Ocean and is associated with coherent SST anomalies from the Arabian Sea to the western Pacific, suggestive of ocean–atmosphere coupling.

Interannual oscillations in an ocean general circulation model coupled to a simple atmosphere model

1989 ◽  
Vol 329 (1604) ◽  
pp. 189-205 ◽  
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
Coupled System ◽  
General Circulation Models ◽  
Atmospheric Model ◽  
Ocean General Circulation Model ◽  
Coupled Oscillations

A model is being developed for tropical air-sea interaction studies that is intermediate in complexity between the large coupled general circulation models (GCMS) that are coming into use, and the simple two-level models with which pioneering El Nino Southern Oscillation studies were done. The model consists of a stripped-down tropical Pacific Ocean GCM, coupled to an atmospheric model that is sufficiently simple that steady-state solutions may be found for low-level flow and surface stress, given oceanic boundary conditions. This permits examination of the nature of interannual coupled oscillations in the absence of atmospheric noise. In preliminary tests of the model the coupled system is found to undergo a Hopf bifurcation as certain parameters are varied, giving rise to sustained three to four year oscillations. For stronger coupling, a secondary bifurcation yields six month coupled oscillations during the warm phase of the El Nino-period oscillation. Such variability could potentially affect the predictability of the coupled system.

scholarly journals Extratropical Influences on the El Niño–Southern Oscillation through the Late Quaternary

2007 ◽  
Vol 20 (5) ◽  
pp. 788-800 ◽  
Author(s):  
Andrew B. G. Bush
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Late Quaternary ◽  
Circulation Model ◽  
Linear Stability Theory ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Enso Events

Abstract A sequence of numerical simulations with a coupled atmosphere–ocean general circulation model configured for particular times during the late Quaternary shows that simulated El Niño–Southern Oscillation (ENSO) events decrease in frequency from the Last Glacial Maximum (LGM) to today, in accord with linear stability theory, but increase in amplitude. Diagnostic analyses indicate that altered momentum fluxes from midlatitude eddy activity caused by changes in orbital forcing (in the Holocene) and topographic forcing (at the LGM) regulate the strength of climatological easterlies and therefore affect both the tropical mean state and the characteristics of interannual variability. The fact that climatic teleconnections associated with paleo-ENSO are fundamentally different during these times suggests a way in which to reconcile some of the existing discrepancies amongst interpretations of proxy records and numerical paleoclimate simulations.

scholarly journals Modulation of the Relationship between ENSO and Its Combination Mode by the Atlantic Multidecadal Oscillation

2020 ◽  
Vol 33 (11) ◽  
pp. 4679-4695 ◽  
Author(s):  
Xin Geng ◽  
Wenjun Zhang ◽  
Fei-Fei Jin ◽  
Malte F. Stuecker ◽  
Aaron F. Z. Levine
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
Atlantic Multidecadal Oscillation ◽  
Climate Impacts ◽  
Enso Events ◽  
Combination Mode ◽  
The Relationship

AbstractRecent studies demonstrated the existence of a conspicuous atmospheric combination mode (C-mode) originating from nonlinear interactions between El Niño–Southern Oscillation (ENSO) and the Pacific warm pool annual cycle (AC). Here we find that the C-mode exhibits prominent decadal amplitude variations during the ENSO decaying boreal spring season. It is revealed that the Atlantic multidecadal oscillation (AMO) can largely explain this waxing and waning in amplitude. A robust positive correlation between ENSO and the C-mode is detected during a negative AMO phase but not during a positive phase. Similar results can also be found in the relationship of ENSO with 1) the western North Pacific (WNP) anticyclone and 2) spring precipitation over southern China, both of which are closely associated with the C-mode. We suggest that ENSO property changes due to an AMO modulation play a crucial role in determining these decadal shifts. During a positive AMO phase, ENSO events are distinctly weaker than those in an AMO negative phase. In addition, El Niño events concurrent with a positive AMO phase tend to exhibit a westward-shifted sea surface temperature (SST) anomaly pattern. These SST characteristics during the positive AMO phase are both not conducive to the development of the meridionally asymmetric C-mode atmospheric circulation pattern and thus reduce the ENSO/C-mode correlation on decadal time scales. These observations can be realistically reproduced by a coupled general circulation model (CGCM) experiment in which North Atlantic SSTs are nudged to reproduce a 50-yr sinusoidally varying AMO evolution. Our conclusion carries important implications for understanding seasonally modulated ENSO dynamics and multiscale climate impacts over East Asia.

Predictability of Two Types of El Niño Assessed Using an Extended Seasonal Prediction System by MIROC

2015 ◽  
Vol 143 (11) ◽  
pp. 4597-4617 ◽  
Author(s):  
Yukiko Imada ◽  
Hiroaki Tatebe ◽  
Masayoshi Ishii ◽  
Yoshimitsu Chikamoto ◽  
Masato Mori ◽  
...  
Keyword(s):  
El Niño ◽  
Lead Time ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
Seasonal Prediction ◽  
Ocean General Circulation Model ◽  
Prediction System ◽  
Central Pacific

Abstract Predictability of El Niño–Southern Oscillation (ENSO) is examined using ensemble hindcasts made with a seasonal prediction system based on the atmosphere and ocean general circulation model, the Model for Interdisciplinary Research on Climate, version 5 (MIROC5). Particular attention is paid to differences in predictive skill in terms of the prediction error for two prominent types of El Niño: the conventional eastern Pacific (EP) El Niño and the central Pacific (CP) El Niño, the latter having a maximum warming around the date line. Although the system adopts ocean anomaly assimilation for the initialization process, it maintains a significant ability to predict ENSO with a lead time of more than half a year. This is partly due to the fact that the system is little affected by the “spring prediction barrier,” because increases in the error have little dependence on the thermocline variability. Composite analyses of each type of El Niño reveal that, compared to EP El Niños, the ability to predict CP El Niños is limited and has a shorter lead time. This is because CP El Niños have relatively small amplitudes, and thus they are more affected by atmospheric noise; this prevents development of oceanic signals that can be used for prediction.

scholarly journals El Niño–Southern Oscillation Simulation at 6000 Years before Present with the MRI-CGCM2.3: Effect of Flux Adjustment

2007 ◽  
Vol 20 (11) ◽  
pp. 2484-2499 ◽  
Author(s):  
Akio Kitoh ◽  
Tatsuo Motoi ◽  
Shigenori Murakami
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Before Present ◽  
Equatorial Pacific Ocean ◽  
Flux Adjustment

Abstract Modulation of El Niño–Southern Oscillation at the mid-Holocene [6000 yr before present (6 ka)] is investigated with a coupled ocean–atmosphere general circulation model. The model is integrated for 300 yr with 6-ka and present (0 ka) insolation both with and without flux adjustment, and the effect of flux adjustment on the simulation of El Niño is investigated. The response in the equatorial Pacific Ocean in 6 ka is in favor of weaker El Niño variability resulting from lowered sea surface temperature (SST) and a more diffuse thermocline. Atmospheric sensitivity in 6 ka is larger than that in 0 ka because of increased trade winds, while oceanic sensitivity in 6 ka is weaker than that in 0 ka, resulting from destabilization of the upper ocean, both in the flux- and non-flux-adjusted experiments. However, the use of flux adjustment causes a difference in the total response. El Niño variability in 6 ka does not change much from that in 0 ka with the flux-adjusted case, while the 6-ka El Niño variability is weaker without flux adjustment. Because the observed proxy data suggest weaker El Niño variability in the mid-Holocene, the non-flux-adjusted version gives a more reasonable response despite a larger bias in its basic states, implying that nondistortion of sensitivity to forcing is more important.

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