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Wageningen University (2013)

Using vegetation indices from satellite images to estimate evapotranspiration and vegetation water use in North-Central Portugal

Slik, B. van der

Titre : Using vegetation indices from satellite images to estimate evapotranspiration and vegetation water use in North-Central Portugal

Auteur : Slik, B. van der

Université de soutenance : Wageningen University

Grade : Master of Science (MS) 2013

Résumé
Recent research has shown the remarkable potential of the use of remote sensing in retrieving evapotranspiration from natural and agricultural surfaces. The time courses of the main biophysical variables which affect crop photosynthesis and water consumption can be assessed using remote sensing data that will provide the spatial distribution of these variables over a region of interest (Duchemin et al. 2006). In this context, this study will investigate the feasibility of using vegetation indices Normalized difference vegetation index (NDVI) and Enhanced vegetation index (EVI) derived from MODIS remote sensing data to provide indirect estimates of : (1) crop coefficients, which represent the ratio of effective (EET) to potential evapotranspiration (PET) and (2) crop evapotranspiration (ETc). Discuss the potential of vegetation indices derived from satellite data to do the estimation of crop coefficients and crop evapotranspiration and analyze the dynamics of these paramenters in response to plant phenology and water availability to be used as drought indicators. The NDVI vegetation index showed better reliability for water use from vegetation in the study area than the EVI. Using NDVI, crop coefficient (Kc) and crop evapotranspiration (ETc) time-series from 2002 to 2012 were built for the study sites and compared with the SPI drought index and the results may indicate that the NDVI will be suitable to analyze the impact of the drought on the vegetation. Effective evapotranspiration (EET) patterns derived from the MODIS satellite (land surface evapotranspiration product MOD16) were analyzed and compared with measured effective evapotranspiration from experimental plots, to analyze the reliability of this product in the study area. The MODIS product did not provide satisfying results in showing evapotranspiration patterns that were comparable with EET calculations from the experimental plots but more extensive time-series of MODIS would be recommendable to increase the overlap period of MODIS and field observation EET values.

Mots clés : vegetation / remote sensing / satellite imagery / drought / evapotranspiration / ecohydrology / portugal / tropical forests / forest ecology

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Page publiée le 13 février 2015, mise à jour le 19 octobre 2018