應用現地遙測技術推估水稻蒸發散量

Estimating Rice Paddy Evapotranspiration using Field-based Remote Sensing

賈西亞(Sergio Garcia Jimenez)

指導教授 ： 鄭克聲

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00047

摘要

欲使用現地遙測的方式對作物灌溉做管理，需要先根據實驗區域情況進行現地調查並收集現地資料。 本研究的實驗區域是屬於北台灣的氣候條件，在本研究中，使用現地測量之水稻田的反射光譜和蒸發散資料，計算水稻在四個不同生長階段的植生指數(vegetation indices, VI)和一種新的光譜指數來推估適合此實驗區域的作物係數(crop coefficient, Kc)。在水稻秧苗期、營養生長期和成熟期所推估的作物係數與前人研究的建議參考值十分吻合；然而，在生殖生長期所推估的作物係數卻與前人研究有很大的差異，其原因是由於使用蒸散儀的方法無法有效的反映實際的水稻田土壤的情況。反射光譜波長範圍為350nm到1050nm，並進行平滑及一階微分處理。經由迴歸分析與群集分析反射光譜的主成分，來選出最適當的波長反射率，以比值、差值、常態化差異、和複迴歸計算新組成的植生指數。新組成之植生指數提升了與Kc值間之關聯，但由一階微分處理後新組成之植生指數沒有提升與Kc值間的關聯。

關鍵字

現地遙測 ； 作物蒸發散量 ； 水稻田 ； 植生指數 ； 土水平衡

並列摘要

Management of crop irrigation by using field-based remote sensing requires background data obtained from field experiments carried out under local conditions. In this study, spectral and evapotranspiration data were used to evaluate well-known vegetation indices (VI) and new spectral indicators for estimating current crop coefficient (Kc) in rice paddy under northern Taiwan climatic conditions. Estimated Kc values for the initial, development and late growth stages were very close to those suggested in previous research works, however, the Kc values at the mid-stage greatly differ from previous Kc values, possibly due to lysimeter method did not perfectly match the paddy soil heat conditions in the field. Spectral reflectance (Refl) values were smoothed and first-order derivative spectra (ρ) were calculated for each individual wavelength between 350 and 1050nm. Based on regression relationship analysis and principal component analysis (PCA) of grouped data, the most appropriate wavelengths were selected and new combinations were calculated by using rationing, differencing, normalized differencing and multiple regression. New indicators improve the degree of correlation between Kc and VI while no significant improvements were found for new wavelengths combinations derived from the first-order derivative.

並列關鍵字

field-based remote sensing ； crop evapotranspiration ； rice paddy ； vegetation index ； soil water balance

參考文獻

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