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Distinct Onset Mechanisms of Two Subtypes of CP El Niño and Their Changes in Future Warming


This study analyzes two subtypes of Central Pacific (CP) El Niño and shows that they possess different sea surface temperature evolution patterns in the Indo-Pacific Oceans, distinct generation mechanisms, and can respond differently to global warming. The CP-I type is triggered in the tropical western Pacific by the weaker-than-normal Australian winter monsoon (AM) through a subsurface thermocline mechanism and is accompanied by significant Indian Ocean warming. The CP-II type onsets in the subtropical North Pacific by the Pacific Meridional Mode (PMM) through a surface coupling mechanism and is accompanied by weak warming anomalies in the Indian Ocean. Two climate models projections indicate that the CP-II type may occur more frequently than the CP-I type in the future due to changes in PMM and AM activities, which should weaken El Niño influences on the Indian Ocean and result in more El Niño events that onset from the North American coast.

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