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<p>Two of the key factors that influence the Indian summer monsoon rainfall (ISMR) are the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). The study focuses on assessing the lead/lag relationship between climatic events (ENSO and IOD) and extreme precipitation, specifically at 95th (R95p) and 99th (R99p) percentiles during Positive IOD (pIOD), Negative IOD (nIOD), El Niño, La Niña, and the combination of ENSO and IOD events. The climate indices, Oceanic Niño Index (ONI) and Dipole Mode Index (DMI), have shown a lag relationship with extreme precipitation over all the homogeneous rainfall zones of India from 1955 to 2014 during the Southwest monsoon. However, the Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model ensemble mean (MMEM) indicates a lead relationship in some of the regions. This disparity may be due to the underlying uncertainties associated with CMIP6 simulations of sea surface temperature (SST). The model uncertainty is found to be the major source of uncertainty in long-term SST projections, followed by scenario and ensemble uncertainties. The changes in the extreme precipitation along with the lead/lag relationships were examined under Shared Socioeconomic Pathway 585 (SSP5-8.5). In contrast to historical simulations, the correlation is observed to be high with a time lag for all climatic events. During El Niño, there is a 2-month lag between ONI and extreme precipitation, whereas a 1-month lag is observed during La Niña over the arid NW region.</p>

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Assessing the Relationship Between Extreme Precipitation, ENSO and IOD During the Indian Summer Monsoon Using CMIP6 Simulations

  • 期刊论文

  • 发表日期：

    2025年9月5日

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  • Meera M. Nair,
  • A. Naga Rajesh,
  • T. Kesavavarthini,
  • A. Sabarinath

摘要

Two of the key factors that influence the Indian summer monsoon rainfall (ISMR) are the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). The study focuses on assessing the lead/lag relationship between climatic events (ENSO and IOD) and extreme precipitation, specifically at 95th (R95p) and 99th (R99p) percentiles during Positive IOD (pIOD), Negative IOD (nIOD), El Niño, La Niña, and the combination of ENSO and IOD events. The climate indices, Oceanic Niño Index (ONI) and Dipole Mode Index (DMI), have shown a lag relationship with extreme precipitation over all the homogeneous rainfall zones of India from 1955 to 2014 during the Southwest monsoon. However, the Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model ensemble mean (MMEM) indicates a lead relationship in some of the regions. This disparity may be due to the underlying uncertainties associated with CMIP6 simulations of sea surface temperature (SST). The model uncertainty is found to be the major source of uncertainty in long-term SST projections, followed by scenario and ensemble uncertainties. The changes in the extreme precipitation along with the lead/lag relationships were examined under Shared Socioeconomic Pathway 585 (SSP5-8.5). In contrast to historical simulations, the correlation is observed to be high with a time lag for all climatic events. During El Niño, there is a 2-month lag between ONI and extreme precipitation, whereas a 1-month lag is observed during La Niña over the arid NW region.