蒸發散量(Evapotranspiration)為水平衡重要之一環。傳統經常利用蒸發皿量測結果或利用相關經驗公式推估結果應用到整個研究集水區，並無法反應出集水區的實際狀況。近年來，由於遙測技術的進步，利用衛星遙測估算蒸發散，可由傳統的「點」觀測拓展至整個集水區的「面」觀測。因此，本研究目的為利用MODIS衛星影像配合Penman-Monteith公式及地表能量平衡模式來估算潛勢蒸發散量，並討論不同估算方法中各氣象因子對潛勢蒸發散估算結果之影響。

　　MODIS感測器具有多個波段，可供組合之分析方式較多樣，因此本研究採用MODIS影像進行潛勢蒸發散量推估，首先針對影像進行前處理，利用濾雲後氣象站無雲像元之輻射強度及亮度溫度與地面觀測資料，建立各氣象因子迴歸式，並採用Penman-Monteith、SEBAL及S-SEBI三種估算蒸發散方法，估算台灣西半部各氣象站潛勢蒸發散量，再根據兩種評鑑指標優選適合台灣西半部地區遙測資料估算潛勢蒸發散量之方法。

　　研究結果顯示以Penman-Monteith法較適合遙測資料估算潛勢蒸發散量。再者討論不同估算方法中各氣象因子對估算結果之影響，結果發現各方法之主要誤差來源分別為：Penman-Monteith主要來自淨輻射量及風速的影響；SEBAL模式則為淨輻射量及動量粗糙長度；而S-SEBI模式則因影像解析度不足所造成乾濕控制線的不確定性。本文應用MODIS影像估算潛勢蒸發散量之方法，可供相關領域學者未來研究之參考。

　Evapotranspiration is one of the important factors in water budget analysis. Pan observation or the empirical evapotranspiration calculation is traditional used as regional evapotranspiration in Taiwan. Recently, the technique of remote sensing (RS) has been widely applied in hydrology. Hence, the study is aimed to estimate regional potential evapotranspiration using RS based on both Penman-Monteith and surface energy balance methods. The influences of meteorological factors on results of potential evapotranspiration from various methods were also discussed.

　MODIS sensor has many bands to provide more information for analyzing. Therefore, we chose MODIS images to estimate potential evapotranspiration. First, the pre-processing of MODIS images and cloud filtering were first proceeded. Then, the regression relationships of meteorological factors were established by using radiance, brightness temperature and meteorological data observed at ground weather stations. In this study, Penman-Monteith, SEBAL and S-SEBI, were compared for estimating potential evapotranspiration over western Taiwan.

　The validation results from 14 meteorological stations showed that Penman-Monteith method has more reliable estimation than surface energy balance models. We also found that estimation of Penman-Monteith method is majorly influenced by net radiation and wind speed. The SEBAL mode is affected by the net radiation and momentum roughness length. The accuracy of S-SEBI mode is controlled by the radiation and evaporation.

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