scholarly journals Warming Trend of the Indian Ocean SST and Indian Ocean Dipole from 1880 to 2004*

2008 ◽  
Vol 21 (10) ◽  
pp. 2035-2046 ◽  
Author(s):  
Chie Ihara ◽  
Yochanan Kushnir ◽  
Mark A. Cane
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Warming Trend ◽  
Positive Events ◽  
The Pacific ◽  
El Niño Events ◽  
The Indian Ocean ◽  
El Nino Events

Abstract The state of the Indian Ocean dipole representing the SST anomaly difference between the western and southeastern regions of the ocean is investigated using historical SST reconstructions from 1880 to 2004. First, the western and eastern poles of the SST-based dipole mode index are analyzed separately. Both the western and eastern poles display warming trends over this period, particularly after the 1950s. The western pole tends to be anomalously colder than the eastern pole from 1880 to 1919, whereas in the interval 1950–2004 the SST anomalies over the western pole are comparable to those over the eastern pole though there are occasional outliers where the eastern pole is anomalously colder than the western pole. The tendencies of the occurrences of positive and negative dipole events in September–November show three distinct regimes during the period analyzed. In 1880–1919, negative dipole events associated with La Niña events occur more frequently than positive events. In 1920–49, some weak positive events occur relatively independently of El Niño events over the Pacific. The period of 1960–2004 is characterized by strong and frequent occurrences of positive events associated with El Niño events.

Different impacts of various El Niño events on the Indian Ocean Dipole

2013 ◽  
Vol 42 (3-4) ◽  
pp. 991-1005 ◽  
Author(s):  
Xin Wang ◽  
Chunzai Wang
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
El Niño Events ◽  
The Indian Ocean ◽  
El Nino Events

Indian Ocean Variability in the GFDL Coupled Climate Model

2007 ◽  
Vol 20 (13) ◽  
pp. 2895-2916 ◽  
Author(s):  
Qian Song ◽  
Gabriel A. Vecchi ◽  
Anthony J. Rosati
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Deep Convection ◽  
Warm Pool ◽  
Surface Winds ◽  
Pacific Warm Pool ◽  
El Niño Events ◽  
The Indian Ocean ◽  
El Nino Events

Abstract The interannual variability of the Indian Ocean, with particular focus on the Indian Ocean dipole/zonal mode (IODZM), is investigated in a 250-yr simulation of the GFDL coupled global general circulation model (CGCM). The CGCM successfully reproduces many fundamental characteristics of the climate system of the Indian Ocean. The character of the IODZM is explored, as are relationships between positive IODZM and El Niño events, through a composite analysis. The IODZM events in the CGCM grow through feedbacks between heat-content anomalies and SST-related atmospheric anomalies, particularly in the eastern tropical Indian Ocean. The composite IODZM events that co-occur with El Niño have stronger anomalies and a sharper east–west SSTA contrast than those that occur without El Niño. IODZM events, whether or not they occur with El Niño, are preceded by distinctive Indo-Pacific warm pool anomaly patterns in boreal spring: in the central Indian Ocean easterly surface winds, and in the western equatorial Pacific an eastward shift of deep convection, westerly surface winds, and warm sea surface temperature. However, delayed onsets of the anomaly patterns (e.g., boreal summer) are often not followed by IODZM events. The same anomaly patterns often precede El Niño, suggesting that the warm pool conditions favorable for both IODZM and El Niño are similar. Given that IODZM events can occur without El Niño, it is proposed that the observed IODZM–El Niño relation arises because the IODZM and El Niño are both large-scale phenomena in which variations of the Indo-Pacific warm pool deep convection plays a central role. Yet each phenomenon has its own dynamics and life cycle, allowing each to develop without the other. The CGCM integration also shows substantial decadal modulation of the occurrence of IODZM events, which is found to be not in phase with that of El Niño events. There is a weak, though significant, negative correlation between the two. Moreover, the statistical relationship between the IODZM and El Niño displays strong decadal variability.

scholarly journals Differences in the Initiation and Development of the Madden–Julian Oscillation over the Indian Ocean Associated with Two Types of El Niño

2017 ◽  
Vol 30 (4) ◽  
pp. 1397-1415 ◽  
Author(s):  
Pang-Chi Hsu ◽  
Ting Xiao
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Radiative Heating ◽  
Madden Julian Oscillation ◽  
Cp El Niño ◽  
El Niño Events ◽  
The Indian Ocean ◽  
Ep El Niño ◽  
El Nino Events

Abstract The influences of different types of Pacific warming, often classified as the eastern Pacific (EP) and central Pacific (CP) El Niño events, on Madden–Julian oscillation (MJO) activity over the Indian Ocean were investigated. Accompanied by relatively unstable (stable) atmospheric stratification induced by enhanced (reduced) moisture and moist static energy (MSE) in the lower troposphere, strengthened (weakened) MJO convection was observed in the initiation and eastward-propagation stages during CP (EP) El Niño events. To examine the key processes resulting in the differences in low-level moistening and column MSE anomalies over the Indian Ocean associated with the two types of El Niño, the moisture and column MSE budget equations were diagnosed using the reanalysis dataset ERA-Interim. The results indicate that the enhanced horizontal advection in the CP El Niño years plays an important role in causing a larger moisture and MSE growth rate over the MJO initiation area during CP El Niño events than during EP El Niño events. The increases in horizontal moisture and MSE advection primarily result from advection by mean flow across the enhanced intraseasonal moisture and MSE gradient, as well as by intraseasonal circulation across the mean moisture and MSE gradient associated with the CP El Niño. In the eastward development stage, the enhanced preconditioning comes from positive moisture and MSE advection anomalies in the CP El Niño events. Meanwhile, the strengthened MJO-related convection over the central-eastern Indian Ocean is maintained by increased atmospheric radiative heating and surface latent heat flux during the CP El Niño compared to the EP El Niño events.

The Influence of the Indian Ocean Dipole on Antarctic Sea Ice*

2015 ◽  
Vol 28 (7) ◽  
pp. 2682-2690 ◽  
Author(s):  
M. Nuncio ◽  
Xiaojun Yuan
Keyword(s):  
Indian Ocean ◽  
Sea Ice ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
Ross Sea ◽  
El Nino ◽  
Low Pressure ◽  
Weddell Sea ◽  
The Pacific ◽  
The Indian Ocean

Abstract This study explores the impact of the Indian Ocean dipole (IOD) on the Southern Hemisphere sea ice variability. Singular value decomposition (SVD) of September–November sea ice concentration and sea surface temperature (SST) anomalies reveals patterns of El Niño–Southern Oscillation (ENSO) in the Pacific and the IOD in the equatorial Indian Ocean. The relative importance of the IOD’s impact on sea ice in the Pacific sector of Antarctica is difficult to assess for two reasons: 1) ENSO generates larger anomalies in the Pacific and Weddell Sea and 2) many of the positive (negative) IODs co-occur with El Niño (La Niña). West of the Ross Sea, sea ice growth can be attributed to the negative heat fluxes associated with cold meridional flow between high and low pressure cells generated by the effects of the IOD. However, the locations of these positive and negative pressure anomaly centers tend to appear north of the sea ice zone during combined ENSO–IOD events, reducing the influence of the IOD on sea ice. The IOD influence is at a maximum in the region west of the Ross Sea. When ENSO is removed, sea ice in the Indian Ocean (near 60°E) increases because of cold outflows west of low pressure centers while sea ice near 90°E decreases because of the warm advection west of a high pressure center located south of Australia.

scholarly journals Studies of the seasonal prediction of heavy late spring rainfall over southeastern China

2021 ◽  
Author(s):  
Shouwen Zhang ◽  
Hui Wang ◽  
Hua Jiang ◽  
Wentao Ma
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Lead Time ◽  
Heavy Rainfall ◽  
El Nino ◽  
Late Spring ◽  
Southeastern China ◽  
River Region ◽  
El Niño Events ◽  
El Nino Events

AbstractThe late spring rainfall may account for 15% of the annual total rainfall, which is crucial to early planting in southeastern China. A better understanding of the precipitation variations in the late spring and its predictability not only greatly increase our knowledge of related mechanisms, but it also benefits society and the economy. Four models participating in the North American Multi-Model Ensemble (NMME) were selected to study their abilities to forecast the late spring rainfall over southeastern China and the major sources of heavy rainfall from the perspective of the sea surface temperature (SST) field. We found that the models have better abilities to forecast the heavy rainfall over the middle and lower reaches of the Yangtze River region (MLYZR) with only a 1-month lead time, but they failed for a 3-month lead time since the occurrence of the heavy rainfall was inconsistent with the observations. The observations indicate that the warm SST anomalies in the tropical eastern Indian Ocean are vital to the simultaneously heavy rainfall in the MLYZR in May, but an El Niño event is not a necessary condition for determining the heavy rainfall over the MLYZR. The heavy rainfall over the MLYZR in May is always accompanied by warming of the northeastern Indian Ocean and of the northeastern South China Sea (NSCS) from April to May in the models and observations, respectively. In the models, El Niño events may promote the warming processes over the northeastern Indian Ocean, which leads to heavy rainfall in the MLYZR. However, in the real world, El Niño events are not the main reason for the warming of the NSCS, and further research on the causes of this warming is still needed.

scholarly journals Two Independent Triggers for the Indian Ocean Dipole/Zonal Mode in a Coupled GCM

2005 ◽  
Vol 18 (17) ◽  
pp. 3428-3449 ◽  
Author(s):  
Albert S. Fischer ◽  
Pascal Terray ◽  
Eric Guilyardi ◽  
Silvio Gualdi ◽  
Pascale Delecluse
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
Sea Surface ◽  
Dynamical Response ◽  
Thermocline Depth ◽  
Second Phase ◽  
The Indian Ocean

Abstract The question of whether and how tropical Indian Ocean dipole or zonal mode (IOZM) interannual variability is independent of El Niño–Southern Oscillation (ENSO) variability in the Pacific is addressed in a comparison of twin 200-yr runs of a coupled climate model. The first is a reference simulation, and the second has ENSO-scale variability suppressed with a constraint on the tropical Pacific wind stress. The IOZM can exist in the model without ENSO, and the composite evolution of the main anomalies in the Indian Ocean in the two simulations is virtually identical. Its growth depends on a positive feedback between anomalous equatorial easterly winds, upwelling equatorial and coastal Kelvin waves reducing the thermocline depth and sea surface temperature off the coast of Sumatra, and the atmospheric dynamical response to the subsequently reduced convection. Two IOZM triggers in the boreal spring are found. The first is an anomalous Hadley circulation over the eastern tropical Indian Ocean and Maritime Continent, with an early northward penetration of the Southern Hemisphere southeasterly trades. This situation grows out of cooler sea surface temperatures in the southeastern tropical Indian Ocean left behind by a reinforcement of the late austral summer winds. The second trigger is a consequence of a zonal shift in the center of convection associated with a developing El Niño, a Walker cell anomaly. The first trigger is the only one present in the constrained simulation and is similar to the evolution of anomalies in 1994, when the IOZM occurred in the absence of a Pacific El Niño state. The presence of these two triggers—the first independent of ENSO and the second phase locking the IOZM to El Niño—allows an understanding of both the existence of IOZM events when Pacific conditions are neutral and the significant correlation between the IOZM and El Niño.

scholarly journals Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

2013 ◽  
Vol 10 (10) ◽  
pp. 6677-6698 ◽  
Author(s):  
J. C. Currie ◽  
M. Lengaigne ◽  
J. Vialard ◽  
D. M. Kaplan ◽  
O. Aumont ◽  
...  
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Near Surface ◽  
Climate Modes ◽  
The Indian Ocean

Abstract. The Indian Ocean Dipole (IOD) and the El Niño/Southern Oscillation (ENSO) are independent climate modes, which frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled biophysical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997/1998 ENSO and IOD event. Results suggest that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. A negative influence of IOD on chlorophyll concentrations is shown in a region around the southern tip of India in fall. IOD also depresses depth-integrated chlorophyll in the 5–10° S thermocline ridge region, yet the signal is negligible in surface chlorophyll. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Yet unlike most other regions examined, the combined explanatory power of IOD and ENSO in predicting depth-integrated chlorophyll anomalies is relatively low in this region, suggestive that other drivers are important there. We show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. Our results suggest that ENSO and IOD cause significant and predictable regional re-organisation of chlorophyll via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries, ecosystems and carbon budgets.

The Extreme El Niño Events Suppressing the Intraseasonal Variability in the Eastern Tropical Indian Ocean

2020 ◽  
Vol 50 (8) ◽  
pp. 2359-2372
Author(s):  
Gengxin Chen ◽  
Dongxiao Wang ◽  
Weiqing Han ◽  
Ming Feng ◽  
Fan Wang ◽  
...  
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Intraseasonal Variability ◽  
Tropical Indian Ocean ◽  
Ocean Dynamics ◽  
El Niño Events ◽  
Extreme El Niño ◽  
El Nino Events

AbstractIn the eastern tropical Indian Ocean, intraseasonal variability (ISV) affects the regional oceanography and marine ecosystems. Mooring and satellite observations documented two periods of unusually weak ISV during the past two decades, associated with suppressed baroclinic instability of the South Equatorial Current. Regression analysis and model simulations suggest that the exceptionally weak ISVs were caused primarily by the extreme El Niño events and modulated to a lesser extent by the Indian Ocean dipole. Additional observations confirm that the circulation balance in the Indo-Pacific Ocean was disrupted during the extreme El Niño events, impacting the Indonesian Throughflow Indian Ocean dynamics. This research provides substantial evidence for large-scale modes modulating ISV and the abnormal Indo-Pacific dynamical connection during extreme climate modes.

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