The composite analyses during 1950–2016 show that the impacts of El Niño on the western Pacific subtropical high (WPSH) are different among the Eastern Pacific type, Central Pacific type-I (CP-I), and Central Pacific type-II (CP-II). The three types of El Niño produce distinct impacts on WPSH due to the varying importance of the Northwestern Pacific coupling, Indian Ocean capacitor, and Maritime Continent mechanisms. The different enhancements and cancellations among these three mechanisms are related to differences in SST anomaly locations and Indian Ocean conditions among the El Niño types. The CP-II El Niño becomes the most influential type of El Niño, while the CP-I El Niño becomes the least influential type. The different impacts and mechanisms for the CP-I and CP-II types of El Niño imply that these two subtypes of CP El Niño may involve different forcing from the Indian Ocean and extratropical Pacific for their generation.

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.

This study examines a climate model hindcast of the responses of the western Pacific subtropical high (WPSH) to three types of El Niño events: the Eastern Pacific (EP) El Niño and the types I and II of Central Pacific (CP-I and CP-II) El Niño. These El Niño types differ from each other in the central locations and patterns of their sea surface temperature (SST) anomalies. They invoke four different mechanisms to impact the WPSH. Hindcasts produced by the Taiwan Central Weather Bureau (CWB) Climate Forecast System 1-tiered model (TCWB1T1) are analyzed. These hindcasts realistically simulate the impacts on the WPSH during the CP-I El Niño, but overestimate the impacts during the decaying summer of the EP El Niño and during the developing autumn and early winter of the CP-II El Niño. The overestimates are mainly the result of an overly strong Maritime Continent regional circulation mechanism during EP El Niños and an overly strong Indian Ocean capacitor mechanism during CP-II El Niños. Further analyses show that these model biases are related to biases in the simulations of El Niño SST anomalies and the Walker circulation. Both model deficiencies are common to contemporary coupled climate models.