scholarly journals Decadal Shift in El Niño Influences on Indo–Western Pacific and East Asian Climate in the 1970s*

2010 ◽  
Vol 23 (12) ◽  
pp. 3352-3368 ◽  
Author(s):  
Shang-Ping Xie ◽  
Yan Du ◽  
Gang Huang ◽  
Xiao-Tong Zheng ◽  
Hiroki Tokinaga ◽  
...  
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Rossby Waves ◽  
El Nino ◽  
East Asian ◽  
North Indian Ocean ◽  
Ocean Warming ◽  
Interdecadal Change ◽  
Wind Pattern ◽  
The North

Abstract El Niño’s influence on the subtropical northwest (NW) Pacific climate increased after the climate regime shift of the 1970s. This is manifested in well-organized atmospheric anomalies of suppressed convection and a surface anticyclone during the summer (June–August) of the El Niño decay year [JJA(1)], a season when equatorial Pacific sea surface temperature (SST) anomalies have dissipated. In situ observations and ocean–atmospheric reanalyses are used to investigate mechanisms for the interdecadal change. During JJA(1), the influence of the El Niño–Southern Oscillation (ENSO) on the NW Pacific is indirect, being mediated by SST conditions over the tropical Indian Ocean (TIO). The results here show that interdecadal change in this influence is due to changes in the TIO response to ENSO. During the postregime shift epoch, the El Niño teleconnection excites downwelling Rossby waves in the south TIO by anticyclonic wind curls. These Rossby waves propagate slowly westward, causing persistent SST warming over the thermocline ridge in the southwest TIO. The ocean warming induces an antisymmetric wind pattern across the equator, and the anomalous northeasterlies cause the north Indian Ocean to warm through JJA(1) by reducing the southwesterly monsoon winds. The TIO warming excites a warm Kelvin wave in tropospheric temperature, resulting in robust atmospheric anomalies over the NW Pacific that include the surface anticyclone. During the preregime shift epoch, ENSO is significantly weaker in variance and decays earlier than during the recent epoch. Compared to the epoch after the mid-1970s, SST and wind anomalies over the TIO are similar during the developing and mature phases of ENSO but are very weak during the decay phase. Specifically, the southern TIO Rossby waves are weaker, so are the antisymmetric wind pattern and the North Indian Ocean warming during JJA(1). Without the anchor in the TIO warming, atmospheric anomalies over the NW Pacific fail to develop during JJA(1) prior to the mid-1970s. The relationship of the interdecadal change to global warming and implications for the East Asian summer monsoon are discussed.

Strengthening of Tropical Indian Ocean Teleconnection to the Northwest Pacific since the Mid-1970s: An Atmospheric GCM Study*

2010 ◽  
Vol 23 (19) ◽  
pp. 5294-5304 ◽  
Author(s):  
Gang Huang ◽  
Kaiming Hu ◽  
Shang-Ping Xie
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Indian Ocean ◽  
Early Summer ◽  
Interdecadal Change ◽  
Northwest Pacific ◽  
Wind Pattern ◽  
Climate Anomalies

Abstract The correlation of northwest (NW) Pacific climate anomalies during summer with El Niño–Southern Oscillation (ENSO) in the preceding winter strengthens in the mid-1970s and remains high. This study investigates the hypothesis that the tropical Indian Ocean (TIO) response to ENSO is key to this interdecadal change, using a 21-member ensemble simulation with the Community Atmosphere Model, version 3 (CAM3) forced by the observed history of sea surface temperature (SST) for 1950–2000. In the model hindcast, the TIO influence on the summer NW Pacific strengthens in the mid-1970s, and the strengthened TIO teleconnection coincides with an intensification of summer SST variability over the TIO. This result is corroborated by the fact the model’s skills in simulating NW Pacific climate anomalies during summer increase after the 1970s shift. During late spring to early summer, El Niño–induced TIO warming decays rapidly for the epoch prior to the 1970s shift but grows and persists through summer for the epoch occurring after it. This difference in the evolution of the TIO warming determines the strength of the TIO teleconnection to the NW Pacific in the subsequent summer. An antisymmetric wind pattern develops in spring across the equator over the TIO, and the associated northeasterly anomalies aid the summer warming over the north Indian Ocean by opposing the prevailing southwest monsoon. In the model, this antisymmetric spring wind pattern is well developed after but absent before the 1970s shift.

scholarly journals The Indian Ocean Dipole: A Missing Link between El Niño Modokiand Tropical Cyclone Intensity in the North Indian Ocean

Climate ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 38 ◽  
Author(s):  
Kopal Arora ◽  
Prasanjit Dash
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
El Nino ◽  
North Indian Ocean ◽  
Missing Link ◽  
El Niño Modoki ◽  
The North ◽  
The Indian Ocean

This study is set out to understand the impact of El Niño Modoki and the Tropical Cyclone Potential Intensity (TCPI) in the North Indian Ocean. We also hypothesized and tested if the Indian Ocean Dipole (IOD) reveals a likely connection between the two phenomena. An advanced mathematical tool namely the Empirical Mode Decomposition (EMD) is employed for the analysis. A major advantage of using EMD is its adaptability approach to deal with the non-linear and non-stationary signals which are similar to the signals used in this study and are also common in both atmospheric and oceanic sciences. This study has identified IOD as a likely missing link to explain the connection between El Niño Modoki and TCPI. This lays the groundwork for future research into this connection and its possible applications in meteorology.

scholarly journals Linkage between Interannual Variation of the East Asian Intraseasonal Oscillation and Mei-Yu Onset

2018 ◽  
Vol 32 (1) ◽  
pp. 145-160 ◽  
Author(s):  
Yonghong Yao ◽  
Hai Lin ◽  
Qigang Wu
Keyword(s):  
Indian Ocean ◽  
South China Sea ◽  
South China ◽  
El Niño ◽  
El Nino ◽  
East Asian ◽  
Intraseasonal Oscillation ◽  
Eastern Indian Ocean ◽  
Ep El Niño ◽  
Sst Anomalies

AbstractThe mei-yu onset over the middle to lower reaches of the Yangtze River Valley (MLYRV) varies considerably from early June to mid-July, which leads to large interannual changes in rainy-season length, total summer rainfall, and flooding potential. Previous studies have investigated the impact of El Niño–Southern Oscillation (ENSO) on the mei-yu onset. This study shows that a strong (weak) East Asian and western North Pacific (EAWNP) intraseasonal oscillation (ISO) in spring leads to an early (late) onset of the mei-yu over the MLYRV, and this ISO–mei-yu relationship is attributed to different types of ENSO in the preceding winter. A strong EAWNP ISO in spring is related to an eastern Pacific El Niño (EP El Niño) in the previous winter, and negative sea surface temperature (SST) anomalies in the eastern Indian Ocean and the South China Sea (SCS) in May, which can cause an early onset of the South China Sea summer monsoon that also favors an early mei-yu onset. In contrast, a weak EAWNP ISO in spring is associated with a central Pacific El Niño (CP El Niño) before April, but with an EP El Niño after April, and positive SST anomalies in both the eastern Indian Ocean and the SCS in May. A statistical forecast model combining the intensity of spring EAWNP ISO, CP ENSO, and EP ENSO indices shows a high prediction skill of the observed mei-yu onset date.

scholarly journals Intensification and Northward Extension of Northwest Pacific Anomalous Anticyclone in El Niño Decaying Mid-Summer: An Energetic Perspective

2021 ◽  
Author(s):  
Haosu Tang ◽  
Kaiming Hu ◽  
Gang Huang ◽  
Ya Wang ◽  
Weichen Tao
Keyword(s):  
Energy Conversion ◽  
El Niño ◽  
El Nino ◽  
Dominant Role ◽  
North Indian Ocean ◽  
Northwest Pacific ◽  
Mean Flow ◽  
The North ◽  
Anomalous Anticyclone ◽  
Circulation Anomalies

Abstract The Northwest Pacific (NWP) anomalous anticyclone (AAC) intensifies and extends northward from El Niño decaying early to mid- summer despite the dissipating sea surface temperature anomalies in the North Indian Ocean, North Atlantic and tropical NWP. The present study investigates these two intraseasonal variations of AAC from the perspective of energetics. The efficiency of dry energy conversion from background mean flow to perturbations in the El Niño decaying mid-summer is high and well explains the intensification of El Niño-induced circulation anomalies over the East Asia (EA)-NWP. The baroclinic energy conversion plays a more dominant role in this process than barotropic energy conversion. Besides, mean state changes over the EA-NWP from early to mid- summer are found in favor of the northward shift of the preferred latitude of the circulation anomalies. Thus, the El Niño induced circulation anomalies over the EA-NWP are more northward-extended in the later period. Empirical orthogonal function analyses further confirm that the northward extension of El Niño-induced circulation anomalies over the EA-NWP stems from local optimal mode change from early to mid- summer.

scholarly journals Relative role of El Niño and IOD forcing on the southern tropical Indian Ocean Rossby waves

2014 ◽  
Vol 119 (8) ◽  
pp. 5105-5122 ◽  
Author(s):  
Soumi Chakravorty ◽  
C. Gnanaseelan ◽  
J. S. Chowdary ◽  
Jing-Jia Luo
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Rossby Waves ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
Relative Role

Indo-Pacific climate during the decaying phase of the 2015/16 El Niño: role of southeast tropical Indian Ocean warming

2017 ◽  
Vol 50 (11-12) ◽  
pp. 4707-4719 ◽  
Author(s):  
Zesheng Chen ◽  
Yan Du ◽  
Zhiping Wen ◽  
Renguang Wu ◽  
Chunzai Wang
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
Ocean Warming ◽  
Indian Ocean Warming

Predictability of Indian Ocean Dipole (IOD)

2016 ◽  
Author(s):  
Jing-Jia Luo
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
The West ◽  
The North ◽  
The Pacific ◽  
Westerly Winds ◽  
Ocean Atmosphere ◽  
The Indian Ocean

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Climate Science. Please check back later for the full article. The tropical Indian Ocean is unique in several aspects. Unlike the Pacific and the Atlantic Oceans, the Indian Ocean is bounded to the north by a large landmass, the Eurasian continent. The large thermal heat contrast between the ocean in the south and the land in the north induces the world’s strongest monsoon systems in South and East Asia, in response to the seasonal migration of solar radiation. The strong and seasonally reversing surface winds generate large seasonal variations in ocean currents and basin-wide meridional heat transport across the equator. In contrast to the tropical Pacific and the Atlantic, where easterly trade winds prevail throughout the year, westerly winds (albeit with a relatively weak magnitude) blow along the equatorial Indian Ocean, particularly during the boreal spring and autumn seasons, generating the semi-annual Yoshida-Wyrtki eastward equatorial ocean currents. As a consequence of the lack of equatorial upwelling, the tropical Indian Ocean occupies the largest portion of the warm water pool (with Sea Surface Temperature [SST] being greater than 28 °C) on Earth. The massive warm water provides a huge potential energy available for deep convections that significantly affect the weather-climate over the globe. It is therefore of vital importance to discover and understand climate variabilities in the Indian Ocean and to further develop a capability to correctly predict the seasonal departures of the warm waters and their global teleconnections. The Indian Ocean Dipole (IOD) is the one of the recently discovered climate variables in the tropical Indian Ocean. During the development of the super El Niño in 1997, the climatological zonal SST gradient along the equator was much reduced (with strong cold SST anomalies in the east and warm anomalies in the west). The surface westerly winds switched to easterlies, and the ocean thermocline became shallow in the east and deep in the west. These features are reminiscent of what are observed during El Niño years in the Pacific, representing a typical coupled process between the ocean and the atmosphere. The IOD event in 1997 contributed significantly to floods in eastern Africa and severe droughts and bushfires in Indonesia and southeastern Australia. Since the discovery of the 1997 IOD event, extensive efforts have been made to lead the rapid progress in understanding the air-sea coupled climate variabilities in the Indian Ocean; and many approaches, including simple statistical models and comprehensive ocean-atmosphere coupled models, have been developed to simulate and predict the Indian Ocean climate. Essential to the discussion are the ocean-atmosphere dynamics underpinning the seasonal predictability of the IOD, critical factors that limit the IOD predictability (inter-comparison with El Niño-Southern Oscillation [ENSO]), observations and initialization approaches that provide realistic initial conditions for IOD predictions, models and approaches that have been developed to simulate and predict the IOD, the influence of global warming on the IOD predictability, impacts of IOD-ENSO interactions on the IOD predictability, and the current status and perspectives of the IOD prediction at seasonal to multi-annual timescales.

Delayed impact of Indian Ocean warming on the East Asian surface temperature variation in boreal summer

2021 ◽  
pp. 1-40
Author(s):  
Sunyong Kim ◽  
Jong-Seong Kug
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
East Asian ◽  
Negative Relationship ◽  
North Indian Ocean ◽  
Ocean Warming ◽  
Boreal Summer ◽  
Indian Ocean Warming ◽  
Sst Anomaly ◽  
The Relationship

AbstractA significant negative relationship is found between the summer mean North Indian Ocean sea surface temperature (SST) and East Asian surface temperature anomalies. However, the relationship is distinctively different for each month and shows a time-lagged relation rather than a simultaneous one. The North Indian Ocean warming in June is responsible for significant cold anomalies over the Korea-Japan region that peak in July, exhibiting a 1-month leading role. The SST increase is closely associated with enhanced convective activity in the region in June, but the relationship between SST and resultant precipitation is substantially weakened afterward. This dependency of the precipitation sensitivity to SST anomaly is related to the climatological evolution of SST. The relatively low background SST due to the strengthening of southwesterly monsoons in the late summer can weaken the sensitivity of the precipitation to SST anomaly, yet the background SST in June is strong enough to maintain an increased sensitivity of precipitation. Thus, the Indian Ocean warming in June effectively drives atmospheric Kelvin waves that propagate into the equatorial western Pacific. In the western North Pacific (WNP), the resultant Kelvin wave-induced Ekman divergence triggers suppressed convection and anticyclonic anomalies. The WNP suppressed convection and anticyclonic anomalies move slowly northeastward until they are located near 20°N through the local air-sea interaction, and act as a source of the Pacific-Japan teleconnection. This teleconnection pathway brings clod surface anomalies to the Korea-Japan region due to the cyclonic circulation that causes the radiative and horizontal advection.

scholarly journals Indian Ocean Dipolelike Variability in the CSIRO Mark 3 Coupled Climate Model

2005 ◽  
Vol 18 (10) ◽  
pp. 1449-1468 ◽  
Author(s):  
Wenju Cai ◽  
Harry H. Hendon ◽  
Gary Meyers
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
El Niño ◽  
Climate Models ◽  
Rossby Waves ◽  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Sea Surface

Abstract Coupled ocean–atmosphere variability in the tropical Indian Ocean is explored with a multicentury integration of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Mark 3 climate model, which runs without flux adjustment. Despite the presence of some common deficiencies in this type of coupled model, zonal dipolelike variability is produced. During July through November, the dominant mode of variability of sea surface temperature resembles the observed zonal dipole and has out-of-phase rainfall variations across the Indian Ocean basin, which are as large as those associated with the model El Niño–Southern Oscillation (ENSO). In the positive dipole phase, cold SST anomaly and suppressed rainfall south of the equator on the Sumatra–Java coast drives an anticyclonic circulation anomaly that is consistent with the steady response (Gill model) to a heat sink displaced south of the equator. The northwest–southeast tilting Sumatra–Java coast results in cold sea surface temperature (SST) centered south of the equator, which forces anticylonic winds that are southeasterly along the coast, which thus produces local upwelling, cool SSTs, and promotes more anticylonic winds; on the equator, the easterlies raise the thermocline to the east via upwelling Kelvin waves and deepen the off-equatorial thermocline to the west via off-equatorial downwelling Rossby waves. The model dipole mode exhibits little contemporaneous relationship with the model ENSO; however, this does not imply that it is independent of ENSO. The model dipole often (but not always) develops in the year following El Niño. It is triggered by an unrealistic transmission of the model’s ENSO discharge phase through the Indonesian passages. In the model, the ENSO discharge Rossby waves arrive at the Sumatra–Java coast some 6 to 9 months after an El Niño peaks, causing the majority of model dipole events to peak in the year after an ENSO warm event. In the observed ENSO discharge, Rossby waves arrive at the Australian northwest coast. Thus the model Indian Ocean dipolelike variability is triggered by an unrealistic mechanism. The result highlights the importance of properly representing the transmission of Pacific Rossby waves and Indonesian throughflow in the complex topography of the Indonesian region in coupled climate models.

Indian Ocean warming during peak El Niño cools surrounding land masses

2017 ◽  
Vol 51 (5-6) ◽  
pp. 2097-2112 ◽  
Author(s):  
N. Herold ◽  
A. Santoso
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Ocean Warming ◽  
Indian Ocean Warming
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