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• Main Authors: Deng-Jing Chen, 陳登璟
• Other Authors: Pay-Liam Lin
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/58862655900484878044

碩士 === 國立中央大學 === 大氣物理研究所 === 100 === 　　In this research, trends of five climate change indices related to extreme precipitation events in Taiwan are investigated using daily observational records of conventional surface stations from 1950 to 2010. Four indices [simple daily intensity index (SDII), total number of day with precipitation ≥50 mm (R50), annual maximum consecutive 5-day precipitation amount (R5d), and the fraction of annual total precipitation from events exceeding the 1961–90 95th percentile (R95p)] describe the intensity (SDII), frequency (R25), and magnitude (R5d and R95p) of precipitation extremes, and the fifth index [consecutive dry days (CDD)] describes drought conditions. The annual probability density functions (PDFs) of precipitation indices for two epochs (i.e., 1950–80 and 1981–2010) are analyzed. The SDII is then roughly classified into three types: light, moderate, and high intensity. Since the 1980s, there has been a change in the types of precipitation intensity, resulting in more frequent moderate and heavy precipitation and less frequent light precipitation intensity. The other three precipitation-related indices (R25, R5d, and R95p) demonstrate a shift toward the right of the PDF over time, suggesting shorter annual number of days with intense precipitation and smaller consecutive 5-day precipitation amounts and smaller fraction of annual precipitation due to events exceeding the 1961–90 95th percentile from the first to the second epoch. 　　A nonparametric trend analysis is then performed for the entire period and six seasons, namely, spring, meiyu, summer, typhoon, autumn and winter. Long-term upward trends are evident for all five indices except R50. Southeastern Taiwan are dominated by upward trends of CDD (longer consecutive dry days)and downward trends of SDII (less intense precipitation), in particular during spring and winter season. 　　To investigate whether the trends are stable throughout the time, the derivatives of trends for each of the 30-yr running series are calculated (e.g., 1950–79, 1951–80, . . . , 1980–2010) for four precipitation-related indices at each station. For northern (southern) Taiwan, positive (negative) derivatives prevail for CDD in the presence of long term negative (positive) trends in the spring season, suggestive of a phase change in precipitation extremes and such extremes showing an upswing (downswing) recently. For Taiwan, there is also an indication of phase reversal over the last 60 year, with negative derivatives occurring in the presence of the background positive trends.