[Estimating evapotranspiration of plantation with non-uniform terrain based on two-wavelength method.]

Kilometer-scale evapotranspiration is usually estimated by remote sensing images, combined with empirical or semi-empirical models, with results being verified with empirical data. However, it is usually difficult to obtain real-time measurements which can match the pixel scale of remote sensing. We analyzed kilometer-scale evapotranspiration by the combination of near-infrared and microwave technique in the Ecosystem Research Station of the Yellow River in Xiaolangdi, during period of plantation growth (1st July to 19th October 2016). Results showed that the combination of near-infrared and microwave technique could obtain well diurnal cycles in different weather conditions, with the overall energy balance reaching 0.87. The technique was sensitive to the variation of relative humidity of air, but not sensitive to that of soil moisture. The error of estimation was resulted from Bowen ratios and atmospheric stability. Compared with the eddy covariance method, the error was within a reasonable range. As estimated by the two-wavelength method, the maximum daily and total evapotranspiration of the study area was 3.5 mm and 162.4 mm, respectively.