scholarly journals Role of Air–Sea Interaction in the Long Persistence of El Niño–Induced North Indian Ocean Warming*

2009 ◽  
Vol 22 (8) ◽  
pp. 2023-2038 ◽  
Author(s):  
Yan Du ◽  
Shang-Ping Xie ◽  
Gang Huang ◽  
Kaiming Hu
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Circulation Model ◽  
Ocean Dynamics ◽  
Northwest Pacific ◽  
Basin Scale ◽  
The Mean ◽  
Second Peak

Abstract El Niño induces a basin-wide increase in tropical Indian Ocean (TIO) sea surface temperature (SST) with a lag of one season. The north IO (NIO), in particular, displays a peculiar double-peak warming with the second peak larger in magnitude and persisting well through the summer. Motivated by recent studies suggesting the importance of the TIO warming for the Northwest Pacific and East Asian summer monsoons, the present study investigates the mechanisms for the second peak of the NIO warming using observations and general circulation models. This analysis reveals that internal air–sea interaction within the TIO is key to sustaining the TIO warming through summer. During El Niño, anticyclonic wind curl anomalies force a downwelling Rossby wave in the south TIO through Walker circulation adjustments, causing a sustained SST warming in the tropical southwest IO (SWIO) where the mean thermocline is shallow. During the spring and early summer following El Niño, this SWIO warming sustains an antisymmetric pattern of atmospheric anomalies with northeasterly (northwesterly) wind anomalies north (south) of the equator. Over the NIO as the mean winds turn into southwesterly in May, the northeasterly anomalies force the second SST peak that persists through summer by reducing the wind speed and surface evaporation. Atmospheric general circulation model experiments show that the antisymmetric atmospheric pattern is a response to the TIO warming, suggestive of their mutual interaction. Thus, ocean dynamics and Rossby waves in particular are important for the warming not only locally in SWIO but also on the basin-scale north of the equator, a result with important implications for climate predictability and prediction.

Interdecadal Variations in ENSO Teleconnection to the Indo–Western Pacific for 1870–2007

2012 ◽  
Vol 25 (5) ◽  
pp. 1722-1744 ◽  
Author(s):  
J. S. Chowdary ◽  
Shang-Ping Xie ◽  
Hiroki Tokinaga ◽  
Yuko M. Okumura ◽  
Hisayuki Kubota ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Indian Ocean ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Western Pacific ◽  
Northwest Pacific ◽  
Early Twentieth Century ◽  
Late Nineteenth

Slow modulation of interannual variability and its relationship to El Niño–Southern Oscillation (ENSO) is investigated for the period of 1870–2007 using shipboard surface meteorological observations along a frequently traveled track across the north Indian Ocean (NIO; from the Gulf of Aden through Malacca Strait) and the South China Sea (to Luzon Strait). During the decades in the late nineteenth–early twentieth century and in the late twentieth century, the El Niño–induced NIO warming persists longer than during the 1910s–mid-1970s, well into the summer following the peak of El Niño. During the epochs of the prolonged NIO warming, rainfall drops and sea level pressure rises over the tropical northwest Pacific in summer following El Niño. Conversely, during the period when the NIO warming dissipates earlier, these atmospheric anomalies are not well developed. This supports the Indian Ocean capacitor concept as a mechanism prolonging El Niño influence into summer through the persistent Indian Ocean warming after El Niño itself has dissipated. The above centennial modulation of ENSO teleconnection to the Indo–northwest Pacific region is reproduced in an atmospheric general circulation model forced by observed SST. The modulation is correlated not with the Pacific decadal oscillation but rather with the ENSO variance itself. When ENSO is strong, its effect in the Indo–northwest Pacific strengthens and vice versa. The fact that enhanced ENSO teleconnections occurred 100 years ago during the late nineteenth–early twentieth century indicates that the recent strengthening of the ENSO correlation over the Indo–western Pacific may not entirely be due to global warming but reflect natural variability.

scholarly journals Predictability of the California Niño/Niña*

2015 ◽  
Vol 28 (18) ◽  
pp. 7237-7249 ◽  
Author(s):  
Takeshi Doi ◽  
Chaoxia Yuan ◽  
Swadhin K. Behera ◽  
Toshio Yamagata
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Regional Climate ◽  
Circulation Model ◽  
Seasonal Prediction ◽  
La Niña ◽  
Boreal Summer ◽  
La Nina ◽  
Basin Scale

Abstract Predictability of a recently discovered regional coupled climate mode called the California Niño (Niña) off Baja California and California is explored using a seasonal prediction system based on the Scale Interaction Experiment-Frontier, version 1 (SINTEX-F1) coupled ocean–atmosphere general circulation model. Because of the skillful prediction of basin-scale El Niño (La Niña), the California Niño (Niña) that co-occurs with El Niño (La Niña) with a peak in boreal winter is found to be predictable at least a couple of seasons ahead. On the other hand, the regional coupled phenomenon peaking in boreal summer without co-occurrence with El Niño (La Niña) is difficult to predict. The difficulty in predicting such an intrinsic regional climate phenomenon may be due to model deficiency in resolving the regional air–sea–land positive feedback processes. The model may also underestimate coastal Kelvin waves with a small offshore scale, which may play an important role in the generation of the California Niño/Niña. It may be improved by increasing horizontal resolution of the ocean component of the coupled model. The present study may provide a guideline to improve seasonal prediction of regional climate modes for important industrial as well as social applications.

scholarly journals Stratospheric Communication of El Niño Teleconnections to European Winter

2009 ◽  
Vol 22 (15) ◽  
pp. 4083-4096 ◽  
Author(s):  
C. J. Bell ◽  
L. J. Gray ◽  
A. J. Charlton-Perez ◽  
M. M. Joshi ◽  
A. A. Scaife
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Circulation Model ◽  
Active Role ◽  
Late Winter ◽  
The Mean ◽  
Mean State

Abstract The stratospheric role in the European winter surface climate response to El Niño–Southern Oscillation sea surface temperature forcing is investigated using an intermediate general circulation model with a well-resolved stratosphere. Under El Niño conditions, both the modeled tropospheric and stratospheric mean-state circulation changes correspond well to the observed “canonical” responses of a late winter negative North Atlantic Oscillation and a strongly weakened polar vortex, respectively. The variability of the polar vortex is modulated by an increase in frequency of stratospheric sudden warming events throughout all winter months. The potential role of this stratospheric response in the tropical Pacific–European teleconnection is investigated by sensitivity experiments in which the mean state and variability of the stratosphere are degraded. As a result, the observed stratospheric response to El Niño is suppressed and the mean sea level pressure response fails to resemble the temporal and spatial evolution of the observations. The results suggest that the stratosphere plays an active role in the European response to El Niño. A saturation mechanism whereby for the strongest El Niño events tropospheric forcing dominates the European response is suggested. This is examined by means of a sensitivity test and it is shown that under large El Niño forcing the European response is insensitive to stratospheric representation.

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.

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.

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 Influence of the Seasonal Cycle on the Termination of El Niño Events in a Coupled General Circulation Model

2006 ◽  
Vol 19 (9) ◽  
pp. 1850-1868 ◽  
Author(s):  
Matthieu Lengaigne ◽  
Jean-Philippe Boulanger ◽  
Christophe Menkes ◽  
Hilary Spencer
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Circulation Model ◽  
Coupled System ◽  
Equatorial Pacific ◽  
Boreal Winter ◽  
Coupled General Circulation Model ◽  
El Niño Events ◽  
El Nino Events

Abstract In this study, the mechanisms leading to the El Niño peak and demise are explored through a coupled general circulation model ensemble approach evaluated against observations. The results here suggest that the timing of the peak and demise for intense El Niño events is highly predictable as the evolution of the coupled system is strongly driven by a southward shift of the intense equatorial Pacific westerly anomalies during boreal winter. In fact, this systematic late-year shift drives an intense eastern Pacific thermocline shallowing, constraining a rapid El Niño demise in the following months. This wind shift results from a southward displacement in winter of the central Pacific warmest SSTs in response to the seasonal evolution of solar insolation. In contrast, the intensity of this seasonal feedback mechanism and its impact on the coupled system are significantly weaker in moderate El Niño events, resulting in a less pronounced thermocline shallowing. This shallowing transfers the coupled system into an unstable state in spring but is not sufficient to systematically constrain the equatorial Pacific evolution toward a rapid El Niño termination. However, for some moderate events, the occurrence of intense easterly wind anomalies in the eastern Pacific during that period initiate a rapid surge of cold SSTs leading to La Niña conditions. In other cases, weaker trade winds combined with a slightly deeper thermocline allow the coupled system to maintain a broad warm phase evolving through the entire spring and summer and a delayed El Niño demise, an evolution that is similar to the prolonged 1986/87 El Niño event. La Niña events also show a similar tendency to peak in boreal winter, with characteristics and mechanisms mainly symmetric to those described for moderate El Niño cases.

An Analysis of the Linkage of Pacific Subtropical Cells with the Recharge–Discharge Processes in ENSO Evolution

2015 ◽  
Vol 28 (9) ◽  
pp. 3786-3805 ◽  
Author(s):  
Han-Ching Chen ◽  
Chung-Hsiung Sui ◽  
Yu-Heng Tseng ◽  
Bohua Huang
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Causal Relation ◽  
Circulation Model ◽  
Transport Processes ◽  
Water Volume ◽  
Time Lags ◽  
Wind Stress Curl ◽  
Time Intervals

Abstract The Simple Ocean Data Assimilation, version 2.2.4 (SODA 2.2.4), analysis for the period of 1960–2010 is used to study the variability of Pacific subtropical cells (STCs) and its causal relation with tropical climate variability. Results show that the interior STC transport into the equatorial basin through 9°S and 9°N is well connected with equatorial sea surface temperature (SST) (9°S–9°N, 180°–90°W). The highest correlation at interannual time scales is contributed by the western interior STC transport within 160°E and 130°W. It is known that the ENSO recharge–discharge cycle experiences five stages: the recharging stage, recharged stage, warmest SST stage, discharging stage, and discharged stage. A correlation analysis of interior STC transport convergence, equatorial warm water volume (WWV), wind stress curl, and SST identifies the time intervals between the five stages, which are 8, 10, 2, and 8 months, respectively. A composite analysis for El Niño–developing and La Niña–developing events is also performed. The composited ENSO evolutions are in accordance with the recharge–discharge theory and the corresponding time lags between the above denoted five stages are 4–12, 6, 2, and 4 months, respectively. For stronger El Niño events, the discharge due to interior STC transport at 9°N terminates earlier than that at 9°S because of the southward migration of westerly winds following the El Niño peak phase. This study clarifies subsurface transport processes and their time intervals, which are useful for refinement of theoretical models and for evaluating coupled ocean–atmosphere general circulation model results.

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