Indian Summer Monsoon and El Niño Southern Oscillation in CMIP5 Models: A Few Areas of Agreement and Disagreement

Gagnon

Siingh

2018

Theor Appl Climatol

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Bias correction of global and regional climate models is essential for credible climate change projections. This study examines the bias of the models of the Coupled Model Inter-comparison Project Phase 5 (CMIP5) in their simulation of the spatial pattern of sea surface temperature (SSTs) in different phases of the El Niño Southern Oscillation (ENSO) and their teleconnections-highlighting the strengths and weaknesses of the models in different oceanic sectors. The comparison between the model outputs and the observations focused on the following three features: (i) the typical horseshoe pattern seen in the Pacific Ocean during ENSO events with anomalies in SSTs opposite to the warm/cool tongue, (ii) different signature in the tropical Pacific Ocean from that of the North and tropical Atlantic Ocean, and (iii) spurious signature in the southern hemisphere beyond 45°S. Using these three cases, it was found that the model simulations poorly matched the observations, indicating that more attention is needed on the tropical/extratropical teleconnections associated with ENSO. More importantly, the observed SST coupling between the tropical Pacific Ocean and the Atlantic Ocean is missing in almost all models, and differentiating the models between high/low top did not improve the results. It also found that SSTs in the tropical Pacific Ocean are relatively well simulated when compared with observation. This work has improved our understanding of the simulation of ENSO and its teleconnections in the CMIP5 models and has raised awareness of the bias existing in the models, which requires further attention by climate modellers.

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confidence: 99%

Evaluating ENSO teleconnections using observations and CMIP5 models

Gagnon

Siingh

2018

Theor Appl Climatol

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“…Various research (Roy 2017;Turner and Annamalai 2012;Annamalai et al 2007) explored model simulations of ISM and ENSO and discussed limitations where models disagree with observation. Here, we studied global hydrological cycle to address further on what areas models agree in general ( Fig.…”

Section: Discussion On Limitations Of Modelsmentioning

confidence: 99%

“…The ENSO can influence seasonal precipitation in various regions of the globe, and Indian summer monsoon (ISM) is one of the most crucial one (e.g. Maity and Kumar 2006;Kripalani and Kulkarni 1997;Roy 2017). It was shown that El Niño (EN) years experience less rain whereas La Niña (LN), more rainfall.…”

Section: Introductionmentioning

confidence: 99%

“…ISM precipitation has likely increased over the last decade, after reversing the drying trend that happened from the mid of the 1970s to the mid of 1990s (IPCC 2013). Roy (2017) and Turner and Annamalai (2012) used CMIP3 and CMIP5 model simulations respectively to examine/ compare ISM precipitation and ENSO with observation. The authors elaborately discussed various issues why models failed to match observations.…”

Section: Introductionmentioning

confidence: 99%

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The role of natural factors (part 2): Indian summer monsoon in climate change period—observation and CMIP5 models

Kripalani

2019

Theor Appl Climatol

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This study discusses the role of natural factors and related teleconnections for Indian summer monsoon (ISM) with a special emphasis on later two decades of the last century. The combined influence of the sun and volcanos on ISM is examined using observational data as well as CMIP5 model outputs. Possible mechanisms relating to a disruption of the usual ENSO-ISM teleconnection for those decades are explored. Observation suggested that the regional Hadley circulation, via the NAO in the northern hemisphere and Indian Ocean Dipole in the southern hemisphere, may have a role in the change in ISM behaviour. Such features though captured well in the observation are shown missing in models. Additionally, it indicates that differences among models mainly originate in a regional level, which could be due to inconsistency in representing regional teleconnection features. Interestingly, all models perform reasonably well in terms of global thermodynamic scaling arguments. The overall study underpins important areas, where natural factors influence regional climate, but models miss out and suggest discrepancies among each other. Such knowledge has major implications in regional as well as global scale. The modelling community will also greatly benefit by an improved representation of ENSO and ISM in models. R. H. Kripalani is retired Senior Scientist,

“…Drought years in India are usually aligned with warm ENSO or El Niño years while excess rainfall years match with La Niña. Several studies have discussed ENSO-ISM teleconnections (Turner et al, 2005;Kumar et al, 2006;Roy, 2017); moreover, few studies also detected some complementary effect on the ISM from the Indian Ocean Dipole (Ashok et al, 2001) and also from the North Atlantic Oscillation (NAO) in the previous seasons (Liu and Yanai, 2001). Such connections were shown to be sensitive to the chosen reference period of the observations (Roy and Collins, 2015).…”

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confidence: 99%

ENSO teleconnections to the Indian summer monsoon under changing climate

Intl Journal of Climatology

Tedeschi

Collins

2019

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The teleconnection between the El Niño–Southern Oscillation (ENSO) and Indian summer monsoon rainfall is analysed in CMIP5 simulations in both historical and future scenario. A subset of models is selected, based on their ability to simulate mean rainfall and the ENSO teleconnection in the historical simulations, and those are used to examine future predictions in the central northeast region of India. For canonical and mixed canonical Modoki ENSO events, the rainfall teleconnection is spatially extended over most of India in the future. For pure Modoki ENSO events, the teleconnection disappears, and practically no influence is detected in any parts of India. Analysis of zonal wind at 200 mb indicates that for the Modoki events, there is a larger spread of changes across the models, while for canonical events there is more inter‐model consistency. A rainfall decomposition technique reveals a battle between changes in circulation which act to weaken the rainfall teleconnection and changes in moisture change which act to strengthen it. The picture is most consistent in the sub‐ensemble of models in the central northeast region but less consistent in regions covering southern India.