On the impacts of the Indian summer monsoon on ENSO in a coupled GCM

Renguang Wu, Ben P. Kirtman

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


This study explores the impacts of the Indian summer monsoon (ISM) on the El Niño-Southern Oscillation (ENSO) evolution by utilizing two coupled general-circulation model simulations. The first simulation uses the Center for Ocean-Land-Atmosphere Studies anomaly-coupled model and the second simulation employs a new coupling strategy, interactive ensembles, that is designed to increase the signal-to-noise ratio of boundary forcing. The effects of monsoon variability related and unrelated to ENSO are separated through composites in terms of both sea surface temperature (SST) over the Niño-3.4 area (170°W-120°W, 5°S-5°N) and Indian summer monsoon rainfall (IMR) anomalies. It is found that ENSO-related monsoon variability has significant impacts on warm events. In the interactive-ensemble simulation, a weak (strong) monsoon enhances (weakens) an ongoing warm event. The monsoon impacts are manifested in the surface zonal wind-stress anomalies in the western central equatorial Pacific. In the anomaly-coupled simulation, the monsoon-ENSO relationship is difficult to detect. The ongoing cold events are only weakly affected by monsoon variability. Monsoon variability that is unrelated to ENSO also induces noticeable SST anomalies in the equatorial central Pacific in the following winter. In the interactive-ensemble model, a weak (strong) monsoon induces noticeable warm (cold) SST anomalies. The long-term change of the ISM-ENSO relationship is also analysed. Fluctuations of the IMR-Niño-3.4 SST correlation are larger in the anomaly-coupled model than in the interactive-ensemble model. No apparent relation is found between the long-term change of the correlation and that of the monsoon and ENSO anomalies or standard deviations. In the interactive-ensemble simulation, the IMR and concurrent El Niño-3.4 SST standard deviations show in-phase long-term changes. In the anomaly-coupled simulation, the long-term changes of the IMR and summer Niño-3.4 SST standard deviations have an out-of-phase relation.

Original languageEnglish (US)
Pages (from-to)3439-3468
Number of pages30
JournalQuarterly Journal of the Royal Meteorological Society
Issue number595 PART B
StatePublished - Oct 1 2003
Externally publishedYes


  • El Niño
  • Long-term change
  • Wind stress

ASJC Scopus subject areas

  • Atmospheric Science


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