| Summary: | 碩士 === 國立臺灣大學 === 大氣科學研究所 === 92 === Abrupt change is characterized by a significant change between the two steady states, continuing more than 5 years. In the present study, we have a start to investigate the 1950’s abrupt change of Taiwan, and research the area of abrupt change and how it happened.
First, by the approach of Yasunaka, we find that the global suddenly change of 1950’s is obvious in temperature but not in sea surface temperature and sea level pressure. Even though that, we still find some place with the shift, like America, Africa and India. Then, we use the method of Yonetani (1992) to detect regional abrupt change, and find an apparent one in east-asia (90°-140°E, 20°-50°N). After regime shift, temperature decreased in most eastern asia, and increased in coast of eastern asia, especially in Kuroshio extension. There was also a tendency that the pressure increased as a whole. Because circulation changed like above, monsoon though which was near Taiwan weakened and temperature difference decreased, monsoon was inferred to descend after 1950’s.
The reason caused abrupt change is discussed. Because the time of abrupt change was close to transition of PDO and the warmth of kuroshio extention was very similar to cold phase of PDO, we try to find the relationship between the abrupt change and Pacific Decadal Oscillation (PDO). To compare the delay viewpoints of Latif et al. (1996)、Deser(1999) and Bo Qiu (2003), we match up the variation of temperature and pressure. Some information searched out that kuroshio extention warmed, with anticyclone on its north, and decadal change of sea surface temperature moved westly then southly after 1947, the transition of PDO. So kuroshio extention and the southern part warmed after 4-5 years, because the reason of delay. Thinking of a point of view above, we consider the 1950’s abrupt change is similar to Deser(1999). So we infer the reason which make the abrupt change happened in east-asia is the delay of PDO, adjusted by rossby wave through 4-5 years.
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