Using MODIS Data to estimate Taiwan Soil Moisture by Evaporative Fraction

• Main Authors: Chi-Hung Chuang, 莊麒弘
• Other Authors: Hwa-Lung Yu
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/xdkz7f

碩士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 105 === Soil water content is one of the important parameters in meteorology, hydrology and agriculture, which affects the operation of the mechanism such as surface water circulation and plant evapotranspiration, and the soil moisture before rainfall is an important reference index on slope disaster. However, the measurement of soil water content is often limited by the spatial limitations of the observation instrument. If the image information obtained by satellite remote sensing technology can be used to estimate the soil water content, the soil moisture content of large area can be obtained. This paper will use the satellite data from the MODIS (Moderate Resolution Imaging Spectroradiometer) to estimate the soil water content. The calculation part of the estimation of soil water content, this paper will use the point of view of evaporation, the calculation of the evaporative fraction. The ratio of actual evapotranspiration and the potential evapotranspiration can be obtained by the relationship of the surface energy balance equation, and the surface energy balance algorithm, SEBAL (Surface Energy Balance Algorithm for Land), is used. Combined with the two-dimensional relationship between the surface temperature and the vegetation index to select the extreme value of the SEBAL algorithm to calculate the evaporative fraction, and then estimate the soil water content. In this paper, we will use the satellite data of MODIS every eight days to calculate the evapotranspiration ratio of Taiwan in 2015 and compare it with the soil moisture content of the soil and water conservation bureau and soil and water conservation station, and then observe the correlation between the two parameters. The results show that the evapotranspiration ratio estimated by satellite telemetry can show the trend of soil water content, and there is a natural logarithm relationship between the two. The correlation coefficient R-square is different due to the different situation of the site of the Soil and Water Conservation Bureau, Between 0.3 and 0.7.