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<p>The South China Sea summer monsoon (SCSSM), recognized as a dominant interannual variability over the western North Pacific (WNP), has been observed to influence the development of the Indian Ocean dipole (IOD) through atmospheric bridges. This study aims to evaluate the performance of the community integrated earth system model (CIESM) in simulating the SCSSM–IOD connection and the underlying mechanisms. The significant correlation coefficients (~ 0.6) between the SCSSM and IOD during boreal summer and autumn are effectively reproduced in the multi-model ensemble (MME) mean from 23 CMIP6 models. These simulations also reasonably capture the atmospheric bridges over the WNP and the southern Maritime Continent, including the precipitation dipole and regional Hadley circulation. Specifically, SCSSM-induced surface wind anomalies over the tropical eastern Indian Ocean amplify local sea surface temperature (SST) anomalies via positive wind–evaporation–SST and wind–thermocline–SST feedbacks, thereby intensifying the zonal SST gradient and promoting the autumnal peak of the IOD. In contrast, the correlation between SCSSM and IOD in the CIESM is significantly higher (~ 0.8), far exceeding both observed values and the MME mean. However, the atmospheric bridges in the CIESM are substantially weakened, largely due to biases in the magnitude and spatial distribution of precipitation anomalies over the WNP. These discrepancies are largely attributed to unrealistic SCSSM–ENSO interactions. In CIESM, ENSO-induced vertical motions over the Maritime Continent strengthen surface zonal winds, particularly in the zonal component, artificially enhancing the SCSSM’s impact on the IOD. Thus, more accurate representation of SCSSM–ENSO relationship in CIESM is essential for improving IOD simulations.</p>

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Simulation of the South China Sea summer monsoon effect on the Indian Ocean dipole in community integrated earth system model

  • 期刊论文

  • 发表日期：

    2025年12月19日

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  • Yazhou Zhang,
  • Yilin Li,
  • Yue Shi,
  • Jianping Li,
  • Bin Zuo,
  • Yang Zhao,
  • Yina Diao,
  • Ting Liu

摘要

The South China Sea summer monsoon (SCSSM), recognized as a dominant interannual variability over the western North Pacific (WNP), has been observed to influence the development of the Indian Ocean dipole (IOD) through atmospheric bridges. This study aims to evaluate the performance of the community integrated earth system model (CIESM) in simulating the SCSSM–IOD connection and the underlying mechanisms. The significant correlation coefficients (~ 0.6) between the SCSSM and IOD during boreal summer and autumn are effectively reproduced in the multi-model ensemble (MME) mean from 23 CMIP6 models. These simulations also reasonably capture the atmospheric bridges over the WNP and the southern Maritime Continent, including the precipitation dipole and regional Hadley circulation. Specifically, SCSSM-induced surface wind anomalies over the tropical eastern Indian Ocean amplify local sea surface temperature (SST) anomalies via positive wind–evaporation–SST and wind–thermocline–SST feedbacks, thereby intensifying the zonal SST gradient and promoting the autumnal peak of the IOD. In contrast, the correlation between SCSSM and IOD in the CIESM is significantly higher (~ 0.8), far exceeding both observed values and the MME mean. However, the atmospheric bridges in the CIESM are substantially weakened, largely due to biases in the magnitude and spatial distribution of precipitation anomalies over the WNP. These discrepancies are largely attributed to unrealistic SCSSM–ENSO interactions. In CIESM, ENSO-induced vertical motions over the Maritime Continent strengthen surface zonal winds, particularly in the zonal component, artificially enhancing the SCSSM’s impact on the IOD. Thus, more accurate representation of SCSSM–ENSO relationship in CIESM is essential for improving IOD simulations.