Analysis of evapotranspiration pattern by SEBAL model during the growing season in the agro-pastoral ecotone in Northwest China

Evapotranspiration(ET) is the major component of water cycle and energy balance in the soil-vegetation-atmosphere system. Accurate estimation of regional ET is crucial to agricultural water allocation and water resources management. Combining the MODIS data and the meteorological observations from national weather stations, this paper used the SEBAL(Surface Energy Balance Algorithms for Land) model of energy balance theory to estimate the ET pattern of agro-pastoral ecotone in Northwest China during the growing season in 2015(April to October). The Penman-Monteith formula(P-M), together with the crop coefficients, was used to compare the ET results by the SEBAL model. The results show that the average absolute error between the SEBAL and the P-M ET values is 0.79 mm/d, the root mean square error(RMSE) is 0.94 mm/d, and R~2=0.76. While slightly higher than the actual ET values, the SEBAL estimated ET values reasonably represent ET pattern in the study region. The range of daily average ET is 0.12-10.66 mm/d, a