陳與汪(2000)的研究指出，1930-1997年期間之臺灣秋季降雨有準20年振盪現象。本 研究主要想瞭解陳與汪(2000)所提出的準20年振盪現象，是否存在長期變遷現象。透過 檢視臺灣全島秋季(9-11月)總降雨及兩種不同類型降雨(颱風降雨和非颱風降雨)在 1945-2015年期間的變化，本研究發現「不論是總降雨或是兩種不同類型降雨，其低頻 擾動都存在週期變遷現象」，在前期(1945-1985年)為準20年振盪現象，經過幾年轉換期 之後，在後期(1990-2015年)為準10年振盪現象。而透過分析10個中央氣象局局屬測站 在1945-2015年期間的降雨資料，本研究發現上述低頻擾動變遷為全島性現象，各地的 振盪週期變化相似，但振幅大小有東、西區域差異(東部的振幅較強，西部的振幅較弱）。 再進一步針對「是由哪些氣候因子影響臺灣秋季降雨之低頻擾動變遷?」這個議題進行 探討，本研究發現「亞洲大陸高壓」和「太平洋副熱帶高壓」這兩個氣候因子的長期變 化，以及「臺灣附近水氣通量」的低頻擾動變化，為影響臺灣秋季降雨之低頻擾動變遷 的可能原因。

This study examines the characteristics of low-frequency variations of autumn (September, October and November) rainfall in Taiwan, during 1945-2015. Analyses focus on the contribution of rainfall from two different types: the typhoon-related rainfall and the nontyphoon-related rainfall. By applying the 5-year running mean analysis on the autumn rainfall, our results showed that the autumn rainfall in Taiwan was dominated by a clear quasi twenty-year oscillation signal before 1985. After 1990, the oscillation period for the low-frequency variation of autumn rainfall was changed to about 10 years. By analyzing the rainfall data from 10 stations of the Central Weather Bureau during 1945-2015, we found that the above phenomenon of low-frequency variations is an island-wide phenomenon. Although the amplitudes of the oscillations vary from place to place, the oscillation period of autumn rainfall is similar for all examined stations in Taiwan. Further examinations on the issue of "What climatic factors affect low-frequency variations of autumn rainfall in Taiwan?" show that the changes of "continental high over China", "Pacific subtropical high", and "moisture flux" are three of important factors affecting the changes in the oscillation period of autumn rainfall (including typhoon-related and non-typhoon-related rainfall) in Taiwan.