scholarly journals Different Types of ENSO Influences on the Indian Summer Monsoon Variability

2012 ◽  
Vol 25 (3) ◽  
pp. 903-920 ◽  
Author(s):  
Renguang Wu ◽  
Jilong Chen ◽  
Wen Chen
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Large Scale ◽  
Southern Oscillation ◽  
Western Indian Ocean ◽  
Air Humidity ◽  
Thermal Contrast ◽  
Preceding Winter ◽  
Sst Anomalies

Abstract Observational analysis reveals three types of El Niño–Southern Oscillation (ENSO) influences on the Indian summer monsoon (ISM): indirect influence of the preceding winter [December–February (DJF)] eastern equatorial Pacific (EEP) sea surface temperature (SST) anomalies (DJF-only cases), direct influence of the concurrent summer [June–September (JJAS)] EEP SST anomalies (JJAS-only cases), and coherent influence of both the preceding winter and concurrent summer EEP SST anomalies (DJF&JJAS cases). The present study distinguishes the three types of ENSO influences and investigates the processes connecting ENSO to the ISM separately. In the DJF-only cases, the preceding winter EEP SST anomalies induce north Indian Ocean (NIO) SST anomalies through air–sea interaction processes in the tropical Indian Ocean. The SST anomalies over the western Indian Ocean alter the surface air humidity there. Both processes favor an anomalous ISM. In the JJAS-only cases, an anomalous ISM is directly induced by ENSO through large-scale circulation changes. The meridional thermal contrast may also contribute to an anomalous ISM. In the DJF&JJAS cases, the preceding winter EEP SST anomalies induce NIO SST anomalies and change the surface air humidity over the western Indian Ocean. Concurrent summer EEP SST anomalies induce large-scale vertical motion anomalies over South Asia. Together, they lead to an anomalous ISM. The anomalous meridional thermal contrast may contribute to an anomalous ISM in late summer. Impacts of the preceding winter EEP SST anomalies in the DJF and JJAS cases may contribute to the contemporaneous correlation between ISM and EEP SST. There are more DJF&JJAS cases before than after the late 1970s. This provides an alternative interpretation for the observed weakening in the ISM–ENSO relationship around the late 1970s.

scholarly journals A Central Indian Ocean Mode and Heavy Precipitation during the Indian Summer Monsoon

2017 ◽  
Vol 30 (6) ◽  
pp. 2055-2067 ◽  
Author(s):  
Lei Zhou ◽  
Raghu Murtugudde ◽  
Dake Chen ◽  
Youmin Tang
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Critical Role ◽  
Western Indian Ocean ◽  
Heavy Precipitation ◽  
Central Indian Ocean ◽  
Monsoonal Precipitation ◽  
Monsoon System ◽  
The Indian Ocean

A central Indian Ocean (CIO) mode is found to play a critical role in driving the heavy precipitation during the Indian summer monsoon (ISM). It is typically denoted with a combination of intraseasonal sea surface temperature (SST) anomalies and intraseasonal wind anomalies over the central Indian Ocean, and it preserves the mechanistic links among various dynamic and thermodynamic fields. Like a T junction, it controls the propagation direction of the intraseasonal variabilities (ISVs) originating in the western Indian Ocean. During the ISM, the CIO mode creates an environment favorable for the northward-propagating mesoscale variabilities. These results unveil the relation between the subseasonal monsoonal precipitation and the CIO mode in the ocean–atmosphere system in the Indian Ocean. The identification of the CIO mode deepens our understanding of the coupled monsoon system and brightens the prospects for better simulation and prediction of monsoonal precipitation in the affected countries.

scholarly journals Role of the Indian Ocean in the Biennial Transition of the Indian Summer Monsoon

2007 ◽  
Vol 20 (10) ◽  
pp. 2147-2164 ◽  
Author(s):  
Renguang Wu ◽  
Ben P. Kirtman
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Indian Monsoon ◽  
Coupled Model ◽  
The Pacific ◽  
The Indian Ocean ◽  
Biennial Variability ◽  
Sst Anomalies

Abstract The biennial variability is a large component of year-to-year variations in the Indian summer monsoon (ISM). Previous studies have shown that El Niño–Southern Oscillation (ENSO) plays an important role in the biennial variability of the ISM. The present study investigates the role of the Indian Ocean in the biennial transition of the ISM when the Pacific ENSO is absent. The influence of the Indian and Pacific Oceans on the biennial transition between the ISM and the Australian summer monsoon (ASM) is also examined. Controlled numerical experiments with a coupled general circulation model (CGCM) are used to address the above two issues. The CGCM captures the in-phase ISM to ASM transition (i.e., a wet ISM followed by a wet ASM or a dry ISM followed by a dry ASM) and the out-of-phase ASM to ISM transition (i.e., a wet ASM followed by a dry ISM or a dry ASM followed by a wet ISM). These transitions are more frequent than the out-of-phase ISM to ASM transition and the in-phase ASM to ISM transition in the coupled model, consistent with observations. The results of controlled coupled model experiments indicate that both the Indian and Pacific Ocean air–sea coupling are important for properly simulating the biennial transition between the ISM and ASM in the CGCM. The biennial transition of the ISM can occur through local air–sea interactions in the north Indian Ocean when the Pacific ENSO is suppressed. The local sea surface temperature (SST) anomalies induce the Indian monsoon transition through low-level moisture convergence. Surface evaporation anomalies, which are largely controlled by surface wind speed changes, play an important role for SST changes. Different from local air–sea interaction mechanisms proposed in previous studies, the atmospheric feedback is not strong enough to reverse the SST anomalies immediately at the end of the monsoon season. Instead, the reversal of the SST anomalies is accomplished in the spring of the following year, which in turn leads to the Indian monsoon transition.

On the relationship between Indian Ocean Dipole, Indian summer monsoon and ENSO

2021 ◽  
Author(s):  
Annalisa Cherchi ◽  
Pascal Terray ◽  
Satyaban Bishoyi Ratna ◽  
Virna Meccia ◽  
Sooraj K.P.
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Indian Ocean Dipole ◽  
Climate Models ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Models ◽  
The Future ◽  
The Indian Ocean

<p>The Indian Ocean Dipole (IOD) is one of the dominant modes of variability of the tropical Indian Ocean and it has been suggested to have a crucial role in the teleconnection between the Indian summer monsoon and El Nino Southern Oscillation (ENSO). The main ideas at the base of the influence of the IOD on the ENSO-monsoon teleconnection include the possibility that it may strengthen summer rainfall over India, as well as the opposite, and also that it may produce a remote forcing on ENSO itself. The Indian Ocean has been experiencing a warming, larger than any other basins, since the 1950s. During these decades, the summer monsoon rainfall over India decreased and the frequency of Indian Ocean Dipole (IOD) events increased. In the future the IOD is projected to further increase in frequency and amplitude with mean conditions mimicking the characteristics of its positive phase. Still, state of the art global climate models have large biases in representing IOD and monsoon mean state and variability, with potential consequences for properties and related teleconnections projected in the future. This works collects a review study of the influence of the IOD on the ISM and its relationship with ENSO, as well as new results on IOD projections comparing CMIP5 and CMIP6 models.</p>

scholarly journals Regional and Local Impacts of the ENSO and IOD Events of 2015 and 2016 on the Indian Summer Monsoon—A Bhutan Case Study

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 954
Author(s):  
Katherine Power ◽  
Josefine Axelsson ◽  
Norbu Wangdi ◽  
Qiong Zhang
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
El Niño ◽  
Late Onset ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Local Scale ◽  
The Indian Ocean

The Indian Summer Monsoon (ISM) plays a vital role in the livelihoods and economy of those living on the Indian subcontinent, including the small, mountainous country of Bhutan. The ISM fluctuates over varying temporal scales and its variability is related to many internal and external factors including the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). In 2015, a Super El Niño occurred in the tropical Pacific alongside a positive IOD in the Indian Ocean and was followed in 2016 by a simultaneous La Niña and negative IOD. These events had worldwide repercussions. However, it is unclear how the ISM was affected during this time, both at a regional scale over the whole ISM area and at a local scale over Bhutan. First, an evaluation of data products comparing ERA5 reanalysis, TRMM and GPM satellite, and GPCC precipitation products against weather station measurements from Bhutan, indicated that ERA5 reanalysis was suitable to investigate ISM change in these two years. The reanalysis datasets showed that there was disruption to the ISM during this period, with a late onset of the monsoon in 2015, a shifted monsoon flow in July 2015 and in August 2016, and a late withdrawal in 2016. However, this resulted in neither a monsoon surplus nor a deficit across both years but instead large spatial-temporal variability. It is possible to attribute some of the regional scale changes to the ENSO and IOD events, but the expected impact of a simultaneous ENSO and IOD events are not recognizable. It is likely that 2015/16 monsoon disruption was driven by a combination of factors alongside ENSO and the IOD, including varying boundary conditions, the Pacific Decadal Oscillation, the Atlantic Multi-decadal Oscillation, and more. At a local scale, the intricate topography and orographic processes ongoing within Bhutan further amplified or dampened the already altered ISM.

The Influence of Tropical Indian Ocean SST on the Indian Summer Monsoon

2007 ◽  
Vol 20 (13) ◽  
pp. 3083-3105 ◽  
Author(s):  
Annalisa Cherchi ◽  
Silvio Gualdi ◽  
Swadhin Behera ◽  
Jing Jia Luo ◽  
Sebastien Masson ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Tropical Indian Ocean ◽  
Tropical Pacific Ocean ◽  
Sst Variability ◽  
The Indian Ocean ◽  
Sst Anomalies ◽  
The Tropical Pacific

Abstract The Indian summer monsoon (ISM) is one of the main components of the Asian summer monsoon. It is well known that one of the starting mechanisms of a summer monsoon is the thermal contrast between land and ocean and that sea surface temperature (SST) and moisture are crucial factors for its evolution and intensity. The Indian Ocean, therefore, may play a very important role in the generation and evolution of the ISM itself. A coupled general circulation model, implemented with a high-resolution atmospheric component, appears to be able to simulate the Indian summer monsoon in a realistic way. In particular, the features of the simulated ISM variability are similar to the observations. In this study, the relationships between the ISM and tropical Indian Ocean (TIO) SST anomalies are investigated, as well as the ability of the coupled model to capture those connections. The recent discovery of the Indian Ocean dipole mode (IODM) may suggest new perspectives in the relationship between ISM and TIO SST. A new statistical technique, the coupled manifold, is used to investigate the TIO SST variability and its relation with the tropical Pacific Ocean (TPO). The analysis shows that the SST variability in the TIO contains a significant portion that is independent from the TPO variability. The same technique is used to estimate the amount of Indian rainfall variability that can be explained by the tropical Indian Ocean SST. Indian Ocean SST anomalies are separated in a part remotely forced from the tropical Pacific Ocean variability and a part independent from that. The relationships between the two SSTA components and the Indian monsoon variability are then investigated in detail.

scholarly journals Impact of Northward-Propagating Intraseasonal Variability on the Onset of Indian Summer Monsoon

2014 ◽  
Vol 27 (1) ◽  
pp. 126-139 ◽  
Author(s):  
Lei Zhou ◽  
Raghu Murtugudde
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Large Scale ◽  
Southern Oscillation ◽  
Indian Subcontinent ◽  
Intraseasonal Variability ◽  
Monsoon Index ◽  
Process Understanding ◽  
Simple Regression Model ◽  
Predictive Understanding

Abstract The onset of the Indian summer monsoon (ISM) has a pronounced interannual variability, part of which originates from the large-scale circulation and its thermodynamic properties. While the northward-propagating intraseasonal variabilities (ISVs) are a prominent characteristic of the ISM, they tend to initiate an early onset by transferring moisture and momentum from the deep tropics to the Indian subcontinent. However, not all early onsets of ISM are attributable to strong ISVs and not all strong ISVs can lead to early ISM onsets. With a daily Indian monsoon index and a simple regression model, the onsets of ISM from 1982 to 2011 are separated into two groups. The years in which the early onsets of ISM are closely related to the northward-propagating ISVs are categorized as the ISVO years, and the other years in which the ISM onsets are not closely related to ISVs are categorized as non-ISVO years. The former category is the focus of this study. Before the onset of ISM in the ISVO years, the convective features are prominent, such as a cyclone over the Bay of Bengal (BoB) and the associated strong convection. The ocean–atmosphere interaction is found to be important for the northward-propagating ISVs before the ISM onset in the ISVO years. Evidence shows that warm SST anomalies drive the atmosphere and lead to atmospheric instability and convection. This reinforces the more recent view that the ocean does not just play a passive role in the northward-propagating ISVs. This process understanding helps shape the path to enhancing predictive understanding and monsoon prediction skills with obvious implications for the prediction of El Niño–Southern Oscillation.

scholarly journals Possible Role of the Indian Ocean in the In-Phase Transition of the Indian-to-Australian Summer Monsoon

2008 ◽  
Vol 21 (21) ◽  
pp. 5727-5741 ◽  
Author(s):  
Renguang Wu
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Southern Oscillation ◽  
Tropical Indian Ocean ◽  
Australian Summer Monsoon ◽  
The Indian Ocean ◽  
Numerical Model Experiments ◽  
Sst Anomalies ◽  
Australian Summer

Abstract Analysis of observations shows that in-phase transitions from the Indian summer monsoon (ISM) to the Australian summer monsoon (ASM) have occurred both in El Niño–Southern Oscillation (ENSO) and non-ENSO years. The present study investigates possible roles of the Indian Ocean in the in-phase ISM-to-ASM transitions. It is shown that an anomalous ISM leads to sea surface temperature (SST) anomalies in the tropical Indian Ocean through wind–evaporation effects. The resultant Indian Ocean SST anomalies induce an anomalous ASM of the same sign as the ISM through an anomalous east–west circulation over the eastern Indian Ocean and the Maritime Continent–northern Australia. The results indicate that the in-phase ISM-to-ASM transitions in non-ENSO years can be accomplished through monsoon–Indian Ocean interactions. The results of observational analysis are confirmed with numerical model experiments.

scholarly journals Atmosphere–ocean dynamics in the Western Indian Ocean recorded in corals

2005 ◽  
Vol 363 (1826) ◽  
pp. 121-142 ◽  
Author(s):  
J. Zinke ◽  
M. Pfeiffer ◽  
O. Timm ◽  
W.–C. Dullo ◽  
G. R. Davies
Keyword(s):  
Indian Ocean ◽  
Time Scales ◽  
Large Scale ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Western Indian Ocean ◽  
Strong Relationship ◽  
Ocean Dynamics ◽  
Climate Factors ◽  
Climate Modes

We present a set of Porites coral oxygen isotope records from the tropical and subtropical Western Indian Ocean covering the past 120–336 years. All records were thoroughly validated for proxy response to regional climate factors and their relation to large–scale climate modes. The records show markedly different imprints of regional climate factors. At the same time, all coral records show clear teleconnections between the Western Indian Ocean and the El Niño–Southern Oscillation (ENSO). The multi–proxy site analysis enables the detection of the covariance structure between individual records and climate modes such as ENSO. This method unravels shifts in ENSO teleconnectivity of the Western and Central Indian Ocean on multi–decadal time–scales (after 1976). The Seychelles record shows a stationary correlation with ENSO, Chagos corals show evidence for non–stationary d 18 O/ENSO relationships and the Southwestern Indian Ocean corals show a strong relationship with ENSO when the forcing is strong (1880–1920, 1970 to present). Our results indicate that the coral δ 18 O, in combination with other proxies, can be used to monitor temporal and spatial variations in the sea–surface temperature and the fresh water balance within the Indian Ocean on interannual to interdecadal time–scales.

scholarly journals VARIABILITY OF INDIAN SUMMER MONSOON : RELATIONSHIP WITH GLOBAL SST ANOMALIES

MAUSAM ◽  
2022 ◽  
Vol 45 (3) ◽  
pp. 205-212
Author(s):  
R. K. VERMA
Keyword(s):  
Indian Ocean ◽  
Long Range ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Atlantic Basin ◽  
Anal Ysis ◽  
The North ◽  
Sst Anomaly ◽  
Sst Anomalies

(iloh,tlcurr("!,1111111 ll111p .o; uflhe SlIllll1lt" r mUn!\4 lOn prt>cipil:lliull anomalies a nti St"a SU l f.IC(" Tt"mpt"1 a1lln"' (SST) a nUllul!it'.'i are pTt'St'IlI("d . n lir1 ) -)l' /u (1950..1479) rime St' 1; ("S uf 11l0n...nnn ind("x b co rn' l a h~d ....; Ih Iht"SST tillll' Sl'riCS al t"nch 1° ;<2° latitLIl1co! u nl:iluJt" box uf th t" \\(1(111 (>I,:eans usi ng COADS (Comprehensive O..:eanAllno...pl1("fl." Dala S('1)dn ta ttl "3riOUS timc IJgs o f lUonth s (i.t' .. l1luI11 h,'S of year s p recedi ng 'lI1.1 conc urrcnI lu Ihe1ll011Stllll1-)l'at) , Ctl lTclal ion..mups :'I ll' pn.-pUTl,.f 111111 Illaly"I'" 1(1 i.lclltify Il' IN."Oll lle ct it ln "-' Ilf llln ll....oon pTt'I,:ipil<ttiunwilh glubal S ~Ts.It is I'olin.! th ai tlll' lag,orrelatiuns .... ilh SST (Will 1:('01(31 and t'ilstt"m t'lluHt orial Padlic (Ninu-rl'l!inniliresuggl·..liw of IWlI I>p t' S o f inlt"raetjuns .....ith Ihe munsoun. The first on e, .... h il.:h sho ws pmili\'c <:orre lnlio n of summermonsoon pf('\.-ipililtion anoll1alit"s ",i lh Ihe ct"nlral and l":Jsl ..-mequaturial P<lciftc SST nnoUlal ies aboul a yea r be forelilt" 1l10 nsollfl. sUggl°.!>1Sthat lhe monsoon which follo ws abmlt a )'t'lir la ll'r ur tX'currence ofwaml t"pisode of EI..Nin~Suut hem Oscillatiun (ENSO) is generally ....-eltc It is also suggestetJ Ihal this inleract io n might be taki ng placelhruugh Ihe in llue nce or nOr1h em hemisp here int er tempera tures. Th e seco nd I)-PC of inleraclion of equ alorialPaci fic SST ....i lh mon soon is revealed through the strung n~al ive co rrela tio ns bqinning befo re lh e summer monsoon an d continuing ....; lh g~ a l er magnitud e an d o~ r ....i der extent. suuest ing th ai a .....arm SST anomaly j ust precedineanll concurrent to monsoon ~aso n weaken s th e monsson.AiNt"li intcf<n'lions bctween Ihe Indian Ocean and monsoon are also emph a si ~d in the anal ysis. Two key~ginns are ide nt ified. Th e cen tra l Indian Ocun south o f th e equalor shoW!strong positive corre la tions during (helalt' no n hl'm ",inler a nd spring. Th e other key Tq!'ion is in the north Ind ian Geran. Th e correlations are significanllynt'ga li\'e. Some teleconnections with th e Atlantic basin are also revealed which are ralhe rdifficuh to explain but ma yfind usefu l ap plications in monitoring and long-range forecas line of the monsoon.

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