Abstract:Based on historical track data of tropical cyclones (TC) in Northwest Pacific, 〖JP2〗ERA Interim reana〖JP〗 lysis dataset and oceanic Ni〖AKn~D〗o indices, the characteristics of tropical cyclones in the Northwest Pacific during the two types of ENSO period are discussed by using statistical methods. The results indicate that the intensity and duration of TC are increasing and severe typhoon activities are more frequent over the Northwest Pacific in summer (SU) El Ni〖AKn~D〗o period. During the occurrence of autumn (AU) El Ni〖AKn~D〗o, the duration and intensity of TC are longer and larger than those generated in SU El Ni〖AKn~D〗o, and the frequency of TC is lower, but the number of super typhoons accounts for one third of total TC, with fewer of TCs landing in China. In addition, the formation positions of TC are more eastward than SU El Ni〖AKn~D〗o. However, the intensity and duration of TC are smaller and shorter, with more low level TCs generated in the SU La Ni〖AKn~D〗a epoch. When the AU La Ni〖AKn~D〗a occurs, the intensity, duration, and TC strength are slightly larger and the generation location is eastward than those TC generated in SU La Ni〖AKn~D〗a period. Further more, it is found that the differences of relative vorticity, vertical shear and SSTA in the Central Pacific are important reasons for the diversification of TC activities during the two types of ENSO, and the intensity and position of subtropical high also have a greater impact on TC activity.