An Exploratory Study of the Relationship between Annual Frequency of Invaded Typhoons in Taiwan and El Nino/Southern Oscillation

聖嬰現象與侵台颱風發生頻率之初步研究

張忍成(Jen-Cheng Joseph Chang)

《Terrestrial, Atmospheric and Oceanic Sciences》 7卷1期 (1996/03) Pp. 83-105

並列摘要

In this study, a nonlinear association between the characteristics of invaded typhoons (hereafter, referred to as ITYs) in Taiwan and sea surface temperature anomalies (SSTAs) over the equatorial eastern Pacific is identified. The relation is such that the years with a warmer-than-normal SSTA condition in the late season generally correspond to fewer annual ITYs (＜4),while those with a cooler SSTA are basically associated with more ITYs (≥4).When the SSTA becomes too cold(≤-1.0℃), however, the annual total number of ITYs is, in fact, greatly reduced (~1-2) instead of being increased.
It is suggested that such a phenomenon is caused by different large-scale atmospheric responses to the underlying sea surface temperature conditions. A lower-level anti-cyclonic circulation with strong divergence suppresses the usual activities of tropical cyclones over the western North Pacific (WNP) in the cold years. An opposite mechanism occurs in the early season of the cool years. During the warm years, the typhoon activities over the WNP are not necessarily suppressed but are rather displaced eastward in response to an anomalous cyclonic circulation over the eastern part of WNP. Under such a configuration, however, Taiwan is not in the path of the preferential storm track.
This observation appears to be useful in the long term forecasting of typhoon activities in the Taiwan area, as long as the SSTAs can be predicted.

並列關鍵字

El Nino/Southern Oscillation ； Invaded typhoons in Taiwan