The Changing Impact Mechanisms of a Diverse El Nino on the Western Pacific Subtropical High

The composite analyses during 1950-2016 show that the impacts of El Nino 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 Nino 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 Nino types. The CP-II El Nino becomes the most influential type of El Nino, while the CP-I El Nino becomes the least influential type. The different impacts and mechanisms for the CP-I and CP-II types of El Nino imply that these two subtypes of CP El Nino may involve different forcing from the Indian Ocean and extratropical Pacific for their generation. Plain Language Summary It is now well recognized that there exists a conventional Eastern Pacific type and an emerging Central Pacific type of El Nino. Recent studies have suggested that the CP El Nino should be further separated into two subtypes. It is shown here that these three El Niho-Southern Oscillation types produce distinct impacts on the western Pacific subtropical high (WPSH). The conventional views of El Nitlo's impacts on the WPSH and their underlying mechanisms need to be revised to take into account of the El Nino diversity. This study also offers new insights into the generation dynamics of the two subtypes of the CP El Nino. We find that the two subtypes of CP El Nino differ not only in their sea surface temperature anomalies in the northeastern Pacific but also in the Indian Ocean.