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Interdecadal modulation of interannual ENSO-Indian summer monsoon rainfall teleconnections in observations and CMIP6 models: Regional patterns
March 02,2021

Nimmakanti Mahendra, Jasti Sriranga Chowdary, Patekar Darshana, Pilli Sunitha, Anant Parekh, Chellappan Gnanaseelan

Published in International Jounal of Climatology, JAN 2021

This study examined the Inter‐decadal modulations of interannual El NiñoSouthern Oscillation (ENSO)Indian Summer Monsoon (ISM) rainfall regional teleconnection patterns in the observations and Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Observations show strong epochal changes of the relationship between ENSO and allIndia summer rainfall (AISR) with weak teleconnections in epoch1 (centred around 1915) and epoch4 (recent epoch) and strong teleconnections in epoch2 (centred around 1940) and epoch3 (centred around 1970) during the study period of 1901–2014. While on the regional point of view, it is found that epochal/decadal ENSO teleconnections to rainfall over northern central India and southern peninsular India are stronger and stable in all epochs. Whereas the rainfalls over the regions like Central India and Eastern Central India (ECI) displayed strong epochal changes in teleconnections, similar to that of AISR. This suggests that changes in ENSOISM rainfall teleconnections are highly influenced by regional rainfall response. Anomalous upward motion over the head Bay of Bengal (BOB) and ECI regions related to Indian Ocean Dipole (IOD) and the westward extension of lowlevel cyclonic circulation from the WesternNorth Pacific (WNP) region are mainly responsible for the epochal changes in regional rainfall patterns over India associated with ENSO. We have assessed the fidelity of 29 CMIP6 models in representing the epochal changes in ENSOmonsoon teleconnections. Nearly, 35% of models simulate epochal changes in teleconnections reasonably well. In most of the models, epochal changes in teleconnections are influenced by the strength and location of largescale subsidence coupled to the strength of Walker circulation associated with ENSO. It is noted that the drivers of epochal changes in ENSOmonsoon teleconnections vary from model to model. Whereas, in the observations, the variance of ENSO itself in summer could influence modulations in the ENSO‐ISM teleconnections apart from IOD and WNP forcing.

Mahendra, N, Chowdary, JS, Darshana, P, Sunitha, P, Parekh, A, Gnanaseelan, C. Interdecadal modulation of interannual ENSOIndian summer monsoon rainfall teleconnections in observations and CMIP6 models: Regional patterns. Int J Climatol. 2021; 41: 2528– 2552. https://doi.org/10.1002/joc.6973.

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