- 學位論文
應用HHT分析洪水與乾旱特性之研究─以石門水庫入流量為例
A Study of Flood and Drought Characteristic Using HHT─A Case Study of Shihmen Reservoir Inflow
摘要
在極端氣候的影響下，雨量與流量在時間與空間上的分佈是否變得較不平均，豐水期的流量是否有增強的可能性，洪水是否有逐年增強的趨勢；另外乾旱現象是否越來越頻繁，連續乾旱的時間是否也越來越長。為了了解極端氣候下臺灣地區洪水與乾旱的特性為何，本研究將石門水庫入流量分為年最大日流量、年濕季總流量、年最長乾旱天數以及年乾季總流量4種方案，分別以希爾伯特-黃轉換(Hilbert-Huang transform, HHT)與傅利葉轉換(Fourier transform)進行時頻分析並將產生出的時頻圖進行比較。當中傅利葉轉換時頻圖所表現出的能量不夠集中，頻率分佈範圍較廣，精確度較低，無法確切的判斷局部時間點上的頻率與能量變化，然而HHT能忠實的呈現頻率交界間的變化，能量較為集中，可用較高的解析度表現出局部時間與頻率之間的關係，因此選擇HHT進行假說檢定分析。 各方案使用移動平均法從時間上進行分組，每次以一組時間的能量做為基準時間，並與其他組時間的能量進行檢定，將各組時間的檢定通過次數各自累加並分析觀察近年來流量所呈現的趨勢、週期，是否呈現加劇或減緩的現象，並且進而探討洪水與乾旱的特性。從年最大日流量與年濕季總流量結果得知，洪水與濕季總流量皆有增強的趨勢；從年最長乾旱天數與年乾季總流量結果得知，近15年，乾旱天數有逐年增加的趨勢，而乾季期間總流量沒有呈現逐漸下降的趨勢。綜合以上觀點，旱澇並存與極端氣候現象逐年顯著。
並列摘要
The influence of the extreme climate on rainfall and flow in time and space distribution are becoming less equal, wet period whether there is an enhanced flow of the possibility of flooding if there is increasing trend year by year; another phenomenon is more frequent droughts, continuous drought whether the time getting longer and longer. In order to understand the extreme weather in Taiwan why the characteristics of flood and drought, in this study, Shihmen Reservoir inflow into annual maximum daily flow, total flow in the wet season, the annual number of days and the longest droughts in the dry season the total flow four kinds of cases, respectively, Hilbert - Huang Transform (HHT) and Fourier transform for generating a time-frequency analysis and time-frequency diagram for comparison. Among the Fourier transform of the time-frequency diagram showing the energy is not enough focus, frequency distribution broader, less accurate, can not determine the exact local time points changes in the frequency and energy, however, faithfully rendering HHT frequency variation between the junction, the energy is more concentrated, higher resolution available locally exhibit the relationship between time and frequency, so choose HHT analysis with test of hypothesis. Cases using the moving average method from the time grouped, each with a set of time as the reference time of the energy group time and energy of the other test, the time of the test in each group the respective accumulated and analyzed by observing the number of flows in recent years emerging trends, period, whether to render exacerbate or mitigate the phenomenon, and then explore the characteristics of flood and drought. From the annual maximum daily flow rate and total flow in the wet season results, floods and wet season total flow individually increasing trend; longest drought in the number of days from the year and the annual dry season, the total flow results, nearly 15 years, droughts have increased year by year the number of days trend, while the total flow during the dry season, did not show a declining trend. Based on the above point of view, the coexistence of droughts and waterlogging with extreme weather phenomena remarkable every year.