The HadISST (Hadley Centre Sea Ice and Sea Surface Temperature) dataset is used to define the years of El Ni？o, El Ni？o Modoki, and La Ni？a events and to find out the impacts of these events on typhoon activity. The results show that the formation positions of typhoon are farther eastward moving in El Ni？o years than in La Ni？a years and much further eastward in El Ni？o Modoki years. The lifetime and the distance of movement are longer, and the intensity of typhoons is stronger in El Ni？o and in El Ni？o Modoki years than in La Ni？a years. The Accumulated Cyclone Energy of typhoon is highly correlated with the Oceanic Ni？o Index with a correlation coefficient of 0.79. We also find that the typhoons anomalously decrease during El Ni？o years but increase during El Ni？o Modoki years. Besides, there are two types of El Ni？o Modoki, I and II. The intensity of typhoon in El Ni？o Modoki I years is stronger than in El Ni？o Modoki II years. Furthermore, the centroid position of the Western Pacific Warm Pool is strongly related to the area of typhoon formation with a correlation coefficient of 0.95. 1. Introduction Recent studies have found that there are two types of El Ni？o in the tropical Pacific, namely: Eastern-Pacific El Ni？o (EP-El Ni？o) and Central-Pacific El Ni？o (CP-El Ni？o) [1, 2]. The EP-El Ni？o is the canonical El Ni？o; a band of anomalous warm ocean water occurs in the eastern tropical Pacific. The CP-El Ni？o is also called El Ni？o Modoki, which is the band of anomalous warm ocean water occurring in the central equatorial Pacific. In this study, to avoid the confusion of the nomenclature used, hareafter the Eastern-Pacific El Ni？o is named as El Ni？o and the Central-Pacific El Ni？o is named as El Ni？o Modoki. The occurrences of anomalous warm water at different regions may cause different changes in air pressure, sea surface height, precipitation, and wind field [3–7]. Yu and Kao [8] and Kao and Yu [9] pointed out that the generation mechanism of the El Ni？o tied to thermocline variations but the El Ni？o Modoki may be affected significantly by atmospheric forcing than by basin-wide thermocline variations. Changes of oceanic environment in El Ni？o and La Ni？a events may alter the formation and intensity of a typhoon because warmer oceanic environment is more suitable for its formation and intensity increase [10–16]. Besides the influence of El Ni？o and La Ni？a events, Wang et al. [17] showed that different impacts of El Ni？o and El Ni？o Modoki events may also change the formation locations, durations, and intensities of tropical cyclones. They
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