Estimation of surface Evapotranspiration in Daxing District based on SEBS model validated by Large Aperture Scintillator

摘要

Evapotranspiration is the main process of water and energy exchange in the hydrosphere, atmosphere and biosphere, and it is also one of the most important components in water cycle. The application of remote sensing technology makes it possible to estimate evapotranspiration at regional scale. Many models have emerged to accurately retrieve evapotranspiration and surface fluxes at different spatial and temporal scales in order to better serve the research and application in related fields. In this study, the temporal and spatial variations of surface energy and evapotranspiration in Daxing District from March to May in 2014 and 2015 (the main growth period of winter wheat) were analyzed using MODIS image and surface energy balance model (SEBS) basedon physical processes at the pixel scale of 1 000 m, combined with local meteorological data and ground observation data. The daily evapotranspiration simulated by SEBS model and measured by large aperture scintillator were validated. The results showedthaUl) Verification of SEBS model inversion results by large aperture scintillator method, the standard errors between the estimated values of SEBS model and the observed values of large aperture scintillator were less than 10% (4% and 9%). The root mean square errors were 2.40 mm/d and 1.26 mm/d, respectively, which have good fitting results (R2=0.8511 and 0.8348), it showed that the method was reasonable and feasible in the study area. 2) Overall, The daily average evapotranspiration of winter wheatin Daxing District in 2014 and 2015 showed a trend of ETaiay > ETAprii> ETMarch, and reached its peak in late May. The average values were 3.82 mm/d and 3.14 mm/d, the maximum values were 6.59 mm/d, 5.57 mm/d, and the minimum values were 1.55 mm/d and 1.36 mm/d, respectively.3) The distribution of evapotranspiration in the study area was highly consistent with that of land use types. The spatial variation trend of daily evapotranspiration was as follows: ETcemrai> ETweatrn> ETEastem.The results can provide scientific reference for the rational allocation and management of water resources in Daxing District of Beijing.