| Summary: | 碩士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 105 === Canopy resistance is a key parameter for implementing the Penman-Monteith equation, which is a well-known method of estimating evapotranspiration. In order to estimate evapotranspiration, it is essential to know the knowledge concerning canopy resistance. Recent research (Pauwels and Samson, 2006) compared different methods of estimating the canopy resistance above a wet sloping grassland and showed that Katerji and Perrier method (Katerji and Perrier, 1983) had better performance on estimating canopy resistance. In this study, we tried to use the same idea and compared six methods to estimate canopy resistance, which are the Jarvis type equation (Jarvis, 1976; Stewart, 1988), the Jarvis-Blanken and Black method (Blanken and Black, 2004), the Todorovic method (Todorovic, 1999), the Katerji and Perrier method, a new approach and constant canopy resistance. The study site was located in County Cork, southwest Ireland(51°〖59〗^'' N 8°〖46〗^'' W), and perennial ryegrass (Lolium perenne L.) was the dominant grass species in this area. An eddy covariance system was used to measure the latent heat flux above this humid grassland. The observed canopy resistance was calculated by rearranging the Penman-Monteith equation combined with the observed latent and sensible heat flux. Our results showed latent heat flux estimation as being less sensitive to the accuracy of canopy resistance predictions. We also found that the Katerji and Perrier method and the new approach have better performance than other methods in estimating the canopy resistance and latent heat flux.
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