- 學位論文
以HHT判斷臺灣河川的豐枯週期
Defining drought and wet seasons in Taiwan using HHT
摘要
在臺灣地區進行水文分析時，通常以降雨量達一定程度作為界定豐枯水期之基準，然因降雨受氣候影響進而推延界定基準之時間同時亦改變豐枯週期，所以並無法精確判定豐枯期距，本研究將臺灣分五大區域取各河川流量資料:北部基隆河、北勢溪、東北部蘭陽溪、中部大安溪、濁水溪、南部高屏溪、東部秀姑巒溪，利用可以處理非線性、非穩態資料的方法將具有訊號水位流量數據利用時頻分析方法Hilbert-Hung Transform(HHT)，做為豐枯水期分析之工具，為解決模態混雜(mode mixing)的問題，使用了整體經驗模式解構法(Ensemble Empirical Model Decomposition(EEMD))，EEMD可將流域內各流量站的流量分離為IMF分量與一條趨勢向量(Residual)，將結果經由希爾伯特轉換求得能量頻譜圖，於頻譜圖用其積分方式求得時間與振幅的邊際時間圖，於發現能量變化與殘值有相關性，故藉由趨勢向量，進而判定河川的豐枯週期。 本研究分析豐枯水期結果與水利署及前人研究比較，由結果證實與雨量界定臺灣豐枯週期的差異不大，然本方法所使用EEMD不但證實過去經驗的可靠性，也可精確判定豐枯週期。
並列摘要
Rainfall variation will change the wet and dry period due to that the rainfall is usually used as a reference to define the period while doing hydrologic analysis in Taiwan which means it is hard to dertermine the period accurately. In this study,we separate Taiwan into five regions and get the flow data of river in these regions: the northern Keelung River、Peishis River, northeast Lanyang River, central Choshui River、Daan River, southern Kaoping River, eastern Hsiukuluan River, use can handle nonlinear and non-stationary method of data will have water flow data signals using time-frequency analysis method Hilbert-Hung Transform (HHT), as the analysis tool of wet and dry period ,for solving the problem of mode mixed, use the Ensemble Empirical Model Decomposition (EEMD), EEMD can be the watershed flow stations separating the IMF component and Residual, the results obtained via the Hilbert transform the energy spectrum, the spectrum diagram with its integral approach time and amplitude obtained marginal time diagram, the discovery of the energy change was correlated with the residual, by the residual, and thus determine the river wet and dry period. This study analyzes the wet and dry period results comparing the Water Resources Agency and previous study as defined by the results confirm and rainfall in Taiwan wet and dry period is insignificant, then the EEMD method not only prove the reliability of past experiences, but also accurately determine wet and dry period.