Relation between the upper ocean heat content in the equatorial Atlantic during boreal spring and the Indian monsoon rainfall during June–September

Pottapinjara, Vijay; Girishkumar, M. S.; Sanikommu, Sivareddy; Ravichandran, M.; Murtugudde, Raghu

doi:10.1002/joc.4506

Cited by 41 publications

(37 citation statements)

References 63 publications

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“…A cold (warm) phase of AZM is defined when the normalized AZM index is lower (greater) than 1 standard deviation. Prior to the analysis, the influence of ENSO is removed (details in supporting information Text S1) from all the variables following the methodology adopted in the previous studies (Pottapinjara et al, ; Sabeerali et al, ). The statistical significance of the correlation analysis is estimated using Pearsons test.…”

Section: Methodsmentioning

confidence: 99%

Atlantic Zonal Mode: An Emerging Source of Indian Summer Monsoon Variability in a Warming World

Sabeerali

Ajayamohan

Bangalath

et al. 2019

Geophysical Research Letters

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Atlantic Zonal Mode (AZM) and Indian summer monsoon rainfall (ISMR) are known to have an inverse relationship, which means that the cold (warm) phases of AZM result in strong (weak) ISMR. Here, we report that the inverse relationship between AZM and ISMR has significantly strengthened in recent decades. The cause of this strengthening relationship has been investigated. We find a robust increase in interannual variability of sea surface temperature over the eastern tropical Atlantic Ocean in recent decades, which implies an increase in the number of strong AZM events toward the end of the twentieth century. The increase in strong AZM events alters the large‐scale monsoon circulation over the Indian subcontinent by enhancing the Kelvin wave response into the Indian Ocean, leading to an enhanced AZM‐ISMR teleconnection. This demands a better representation of the AZM‐ISMR teleconnection in climate models for improving seasonal monsoon prediction in a warming world.

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Section: Methodsmentioning

confidence: 99%

Atlantic Zonal Mode: An Emerging Source of Indian Summer Monsoon Variability in a Warming World

Sabeerali

Ajayamohan

Bangalath

et al. 2019

Geophysical Research Letters

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“…Chattopadhyay et al, 2015). Recently, also the tropical South Atlantic (TSA) and the Atlantic zonal mode have been identified as source for Indian monsoon variability and predictability (Kucharski et al, 2007(Kucharski et al, , 2008Losada et al, 2010;Barimalala et al, 2011;Pottapinjara et al, 2014Pottapinjara et al, , 2015. It should be noted that the TSA and Atlantic zonal mode are closely related (Wang et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…The impact from other ocean basins is of secondary importance. On the other hand, the correct representation of these other teleconnections could provide improved predictability of the Indian monsoon, particularly in non-ENSO years (Pottapinjara et al, 2014(Pottapinjara et al, , 2015. The TSA-Indian monsoon teleconnection has also been identified as the leading mode in the coupled variability between the tropical Atlantic region and the Indian monsoon (Syed and Kucharski, 2016).…”

Section: Introductionmentioning

confidence: 99%

Influence of tropical South Atlantic sea‐surface temperatures on the Indian summer monsoon in CMIP5 models

Kucharski

Joshi

2017

Quart J Royal Meteoro Soc

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In this study the teleconnection from the tropical South Atlantic to the Indian monsoon has been assessed in observations and in 32 models from the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project Phase 5 (CMIP5). All models show that the regression pattern of tropics‐wide Atlantic sea‐surface temperature (SST) anomalies onto the tropical South Atlantic index correlates well with that in observations, even though with varying spatial standard deviations. However, only about half of the 32 models considered show the correct sign of rainfall response over India to a warm anomaly in the south tropical Atlantic, which is a reduction of rainfall. On the other hand, models generally do show large‐scale responses broadly consistent with the observations, and the signal over India depends on relatively subtle changes in the response. This response to a tropical South Atlantic warm (cold) anomaly is a low‐level quadrupole in stream function with an anticyclonic (cyclonic) anomaly over the Arabian Sea and India. This anticyclonic (cyclonic) anomaly leads to a weakening (strengthening) of the Somali jet and low‐level divergence (convergence) over India, both inducing a reduction (an increase) of Indian rainfall. The models which do not show the correct rainfall response over India also show a response similar to the one indicated above, but with maximum of the anticyclonic (cyclonic) response shifted to the western Pacific. The large‐scale Walker circulation adjustment to the tropical South Atlantic SST anomalies is identified as one of the factors which account for the differences in the low‐level stream‐function response. Models (and the observations) with the correct sign of the rainfall signal over India show the dominant upper‐level convergence (divergence) as response to a warm (cold) tropical South Atlantic in the western Pacific region, whereas models with the wrong sign of the rainfall signal show it predominantly in the central‐eastern Pacific. The fact that such relatively subtle changes in the response lead to a reversal of the rainfall signal over India raises the question about the robustness of the tropical South Atlantic–Indian monsoon teleconnection.

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“…The last four decades of climate research have revealed the influence of the ocean-atmosphere coupled system variability within the tropical Atlantic basin on the observed climate conditions in the adjacent continental regions [1][2][3][4][5][6]. Recent studies have also shown that atmospheric perturbations generated in this region by the ocean-atmosphere coupled variability act as forcing conditions on the El Niño-Southern oscillation (ENSO) [7][8][9][10], Pacific meridional mode [11], North Atlantic oscillation (NAO) [10,12], and Indian monsoon [13,14]. Therefore, a more accurate understanding of the tropical Atlantic variability could improve climate prediction over the adjacent regions, benefiting their 2 of 16 populations, and, from a broader perspective, deepen our understanding of the interactions between the tropical Atlantic variability and diverse large-scale phenomena.…”

Section: Introductionmentioning

confidence: 99%

Analyzing the Influence of the North Atlantic Ocean Variability on the Atlantic Meridional Mode on Decadal Time Scales

et al. 2019

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Important features of the Atlantic meridional mode (AMM) are not fully understood. We still do not know what determines its dominant decadal variability or the complex physical processes that sustain it. Using reanalysis datasets, we investigated the influence of the North Atlantic Ocean variability on the dominant decadal periodicity that characterizes the AMM. Statistical analyses demonstrated that the correlation between the sea surface temperature decadal variability in the Atlantic Ocean and the AMM time series characterizes the Atlantic multidecadal oscillation (AMO). This corroborates previous studies that demonstrated that the AMO precedes the AMM. A causal inference with a newly developed rigorous and quantitative causality analysis indicates that the AMO causes the AMM. To further understand the influence of the subsurface ocean on the AMM, the relationship between the ocean heat content (0–300 m) decadal variability and AMM was analyzed. The results show that although there is a significant zero-lag correlation between the ocean heat content in some regions of the North Atlantic (south of Greenland and in the eastern part of the North Atlantic) and the AMM, their cause-effect relationship on decadal time scales is unlikely. By correlating the AMO with the ocean heat content (0–300 m) decadal variability, the former precedes the latter; however, the causality analysis shows that the ocean heat content variability drives the AMO, corroborating several studies that point out the dominant role of the ocean heat transport convergence on AMO.

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Relation between the upper ocean heat content in the equatorial Atlantic during boreal spring and the Indian monsoon rainfall during June–September

Cited by 41 publications

References 63 publications

Atlantic Zonal Mode: An Emerging Source of Indian Summer Monsoon Variability in a Warming World

Atlantic Zonal Mode: An Emerging Source of Indian Summer Monsoon Variability in a Warming World

Influence of tropical South Atlantic sea‐surface temperatures on the Indian summer monsoon in CMIP5 models

Analyzing the Influence of the North Atlantic Ocean Variability on the Atlantic Meridional Mode on Decadal Time Scales

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