Estimation Of Evapotranspiration In Beijing Plain Afforestation Region Based On SEBAL Model

The land surface evapotranspiration is the primary portion in water balance, and during the process the energy is absorbed and released, evapotranspiration plays an important role in energy balance, so the research of evapotransiration values much[1].The SEBAL(Surface Energy Balance Algorithm for Land)model is one of the most popular remote sensing methods to estimate the evapotranspiration, this method requires only a small number of atmosphere parameter and the data can be easily obtained, besides these advantages, the results have a higher precision and this method can be used in different kinds of terrains. In this paper, the Landsat8 Remote Sensing data is selected in April13,July 25,October 6 in 2014, these three images represent the spring, the summer and the autumn, besides these three images, the same period MODIS L1 B image data are also applied in estimating evapotranspiration, combined with Yanqing Station meteorological data and the land used data, the evapotranspiration of Yangqing Plain Afforestation Project can be obtained based on SEBAL model. According to the FAO-Penman equation provided by World Food and Agriculture Organization, combined with Yanqing Station meteorological data, the potential evapotranspiration can be estimated of Beijing Plain Afforestation Project. Thus the results estimated by Remote Sensing method can be verified, through analysis shows that the SEBAL model can estimate the evapotranspiration in Beijing Plain Afforestation Project effectively.This study mainly includes the two aspects as followings:(1)This paper uses the spatial modeling maker tools of the ERDAS IMAGINE software to achieve the estimation of the main parameters in SEBAL model, thus the daily evapotranspiration in Yanqing plain afforestation area can be achieved. The evapotranspiration which is estimated by remote sensing model is verificated by potential evapotranspiration of FAO-Penman algorithm. From the results, the relative error of April13, July 25 and October 6 is less than 10%. It can be considered that the ultimate estimated accuracy is satisfactory, the SEBAL energy balance model can be used to estimate the regional evapotranspiration in the amount.(2)From the Analysis of the ET. The distribution of ET in the Plains Afforestation area shows the Periodic season in different seasons, in summer the evapotranspiration is the highest, while the spring is the lowest. It can be seen from the distribution of the ET by Remote Sensing method in the same period, the different species of trees have differentevapotranspiration. Where the evapotranspiration of the broad-leaved forests trees,for example the willow, the poplar and the acacia trees, have greater evapotranspiration,than the pine-leaved forests trees, for example the small coniferous. In addition, the evapotranspiration also has a relationship of the age, besides the species. The results show that the evapotranspiration of planted trees increased firstly then decreased with the age of the tree.