The Influence of Two Kinds of El Ni?o Events on the Strong Tropical Cyclone Generation and Strength in the Pacific Ocean

This paper focuses on the effects of two types of El Ni?o events on tropical cyclone activity.We classified El Ni?o events from 1961 to 2015 according to their sea surface temperature(SST) anomalies into an eastern type and a central type.Then we selected strong tropical cyclones to statistically analyze the tropical cyclone characteristics during different events and their effects,as well as to study the possible mechanisms related to thermodynamic and dynamic factors.The tropical cyclone generation areas were found to be very similar during the two kinds of events.The average number of tropical cyclone in the eastern event is more than that in central event,and the hurricane in northeastern Pacific(HNP) has more energy than the typhoon in northwestern Pacific(TNP) in all cases.The seasonal distribution of the TNP high-incidence centers during central El Ni?o events is opposite to that of the HNP.The TNP accumulated cyclone energy(ACE) intensity is similar in the fall and summer,and the HNP ACE intensity in the summer is greater than that in the fall.The SSTs are consistent with the TNP and HNP movement trends.The Walker circulation intensity was strongly affected by the eastern events,but it quickly returned to its normal state,while the intensity was slightly reduced in the central events,and it slowly returned to its normal state.The vertical velocity distributions in the Pacific are different at different stages of both events,and the distributions of vertical velocity anomalies for typhoons and hurricanes are consistent.

This paper focuses on the effects of two types of El Nino events on tropical cyclone activity. We classified El Nino events from 1961 to 2015 according to their sea surface temperature （SST） anomalies into an eastern type and a central type. Then we selected strong tropical cyclones to statistically analyze the tropical cyclone characteristics during different events and their effects, as well as to study the possible mechanisms related to thermodynamic and dynamic factors. The tropical cyclone generation areas were found to be very similar during the two kinds of events. The average number of tropical cyclone in the eastern event is more than that in central event, and the hurricane in northeastern Pacific （HNP） has more energy than the typhoon in northwestern Pacific （TNP） in all cases. The seasonal distribution of the TNP high-incidence centers during central El Nifio events is opposite to that of the HNP. The TNP accumulated cyclone energy （ACE） intensity is similar in the fall and summer, and the HNP ACE intensity in the summer is greater than that in the fall. The SSTs are consistent with the TNP and HNP movement trends. The Walker circulation intensity was strongly affected by the eastern events, but it quickly returned to its normal state, while the intensity was slightly reduced in the central events, and it slowly returned to its normal state. The vertical velocity distributions in the Pacific are different at different stages of both events, and the distributions of vertical velocity anomalies for typhoons and hurricanes are consistent.