A study on the long-term variation of seasonal precipitation in the Taiwan area

• Main Authors: Yi-Ping Ting, 丁一萍
• Other Authors: Chung-Ru Ho
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/41931823634535621032

碩士 === 國立臺灣海洋大學 === 海洋環境資訊學系 === 94 === Abstract The purpose of this study was to explore the variation of seasonal precipitation in Taiwan area from 1965 to 2004. The study data include daily precipitation at 52 stations belonging to the Central Weather Bureau (CWB) and the Water Resources Agency (WRA). The first part of this study was to analyze total typhoons’ precipitation rate within a whole year. The second part of this study was to gather statistics about the nearly ten and the former past thirty years’ seasonal precipitation changes at the 52 stations. The final part of this study was to analyze the spatial and temporal distribution of monthly precipitation and its relationship with El Ni�瓨 episodes by principal component analysis. The results indicated an increasing trend of the nearly ten years’ typhoons, compared with the former past thirty years’ ones. In the nearly ten years, there were 5.5 typhoons in average per year; in the former past thirty years, there were 4.3 typhoons in average per year. The station at Mt. Ali was the most prominently influenced by typhoons’ tracks. Compared with the nearly ten and the past thirty years’ seasonal precipitations; regardless of the northern, the central, and the southern Taiwan, the annual precipitation tended to decrease. Nevertheless, during the northeast monsoon season, the precipitation amounts at central, southern, and eastern Taiwan all increased, and the precipitation days at central Taiwan were obviously reduced. During spring rain season, theses four areas’ precipitation all decreased. During Plum rain season, all theses four areas’ precipitation days and amounts decreased. During typhoon season, the precipitation days at northern Taiwan were obviously increased. The precipitation at central Taiwan increased, and the precipitation at southern Taiwan was slightly decreased. On the whole, the precipitation changes during the typhoon season were milder than the other three rain seasons. As for principal components analysis on precipitation amounts: The first principal component was relevant to the average annual precipitation. The second principal component was closely correlated to the longitude. The principal component value at east was much more than that at west. In the western area of the Mt. Central Range, the principal component value was decreasing from north to south. The third principal component was closely correlated to the latitude. The eastern Taiwan’s boundary line was from Taipei to Ilan, the principal component value at north was much more than that at south. The western Taiwan’s boundary line was from Chiayi to Tainan, the principal component value at north is also much more than that at south. The cross-correlation results between monthly precipitation and El Ni�瓨 events indicated that El Ni�瓨 phenomenon has some effects on Taiwan’s precipitation — the precipitation in Taiwan would be one month earlier than ever. The coefficient correlation was 0.35.