臺灣西南部近五十年颱風降水特徵變化分析

Analysis on Change in Typhoon Rainfall of Southwestern Taiwan during the Recent 50 Years

本研究基於臺灣西南部之臺南、高雄、恆春等三處測候站1960年至2009年間的颱風降水資料，選擇年颱風事件最大總降水量、最大24小時降水量、年高強度颱風降水事件次數及該三項量值之變幅，藉由計量方法檢視區域平均值序列和測站序列的線性趨勢變化與階變特徵，並探討其災害意涵。分析結果顯示，近50年臺灣西南部地區在年颱風事件最大總降水量和最大24小時降水量、年高強度颱風降水次數變幅上未具有顯著的線性趨勢與階變變化。年颱風事件最大總降水量變幅、最大24小時降水量與年高強度颱風降水次數序列後期的集中量值有所增加，階變大多居主要地位，然而階變的升降型態組成和變異時間分布具有較為明顯的隨機性地域差異。年颱風事件的最大總降水量和最大24小時降水量上升趨勢雖不顯著，但因此兩項變數之變幅量值和高強度颱風降水事件的年次數均朝增加的方向變動，代表區內近期較易出現過去少見之極端高總降水量、高降水強度的颱風降水事件，其致災潛勢提高，水文災害風險相對加大，此變化趨向可能延續至短期的未來，亟需加以密切觀察與關注。

In this study, the monotonic trend and step changes within the typhoon rainfall of Southwestern Taiwan during 1960-2009 are desired to be explored. The annual series of maximum total rainfall, 24-hours maximum rainfall, high-intensive rainfall frequency and their amplitudes were selected as indicator variables. Region-based and station-based analyses were carried out for the data of Tainan, Kaohsiung and Hengchun by using some nonparametric statistical methods. At significant level of 0.05 and 0.10 respectively, no changes were detected in the regional or most station series of annual maximum total rainfall, 24-hours maximum rainfall and frequency amplitude of high-intensive rainfall. In contrast, central tendency measure of the other three variables tends to increase recently, and step change is with relative significance widely. There is a randomness property existing in those changes. It is evidently reflected in the local variations of the association of shift direction or change points among stations or them and region. The result of this study also revealed that the occurrence probability of extreme rainfall events derived from typhoon in Southwestern Taiwan seem to be rising recently. Potential of hydrological hazard become higher in short-term scale therefore. The information is important for disasters prevention in the future.