| dc.description.abstract | In Taiwan, approximately 73% of the total water resource is been used for agricultural purposes. Among the 73% of agricultural water usage, more than half of the water is used for the paddy rice irrigation. As a result, it is important to evaluate the evapotranspiration characteristic of the paddy rice fields. Traditionally, evapotranspiration is measured by using basin or empirical function with surface meteorological data. However, these methods only measure points and may not effectively address the evapotranspiration over a large spatial domain. To resolve such issue, using remote sensing technology to estimate the evapotranspiration becomes an interest field, as the remote sensing technology has the advantage of acquiring large surface data instantaneously and the data can be used to retrieve surface parameters, as well as thermal prosperities.
The research presented here is to use satellite images in conjunction with the in-situ surface meteorological measurement, such as temperature and wind velocity, to estimate the surface heat fluxes that include soil heat flux, sensible heat flux, and latent heat flux. This method is based on surface energy balance to estimate the surface heat fluxes. Once the heat fluxes has been determined, the evaporation then can be derived from radiation and evaporation controlled lines.
The satellite data used for this study are the MODIS level 1D image obtaining from CSRSR (Center of Space and Remote Sensing Research), National Central University. In additional, derivative products of the MODIS sensor from USGS/NASA were also obtained for comparative study. The result shows that using MODIS level 1D data as input parameters produces better result and is closer to the ground measurement. Hence, the MODIS level 1D data were used to study the surface heat fluxes of two rice agricultural cycles in 2006. With the correlation coefficient over 0.60, the result shows a potential in estimating the surface heat fluxes of paddy rice fields in Chiayi area, and can be helpful to control the water used to irrigate the paddy rice. | en_US |