%0 Journal Article
%T Impacts of Two Types of El Ni£¿o and La Ni£¿a Events on Typhoon Activity
%A Po-Chun Hsu
%A Chung-Ru Ho
%A Shin-Jye Liang
%A Nan-Jung Kuo
%J Advances in Meteorology
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/632470
%X 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¨C7]. 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¨C16]. 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
%U http://www.hindawi.com/journals/amete/2013/632470/