Research On Retrieving And Spatial-temporal Changes Of Evaporation Estimation In The Yellow River Delta Based On Refined SEBS Model

Evapotranspiration is one important parameter in water cycle, and it affects the redistribution of precipitation and radiant energy on the surface. Effective prediction of the evapotranspiration provides scientific basis for rational use and distribution of water resources, and growing understands water cycle status on the condition of different land use or cover classifications.The Yellow River Delta is located in the connection zone among the Bohai Sea and Dongying City. This vast land is rich in petroleum and natural gas resources. And in this area there is one of the most important marshes in the world : the Yellow River Delta Wetland, which is the most integrated, broadest, youngest wetland ecological system in warm temperate zone of our country.The surface energy balance system model which is the important remote sensing method requires only a small number parameter but have a higher precision. Instantaneous evapotranspiration when the satellite passed can be computed only by inputting the satellite images, digital elevation data and some meteorological data in this model.In this paper, the evapotranspiration of nature vegetation in Yellow River Delta is caculated by using meteorological data, digital elevation data and Landsat-5 TM Image and based on the theory of surface energy balance system. The basic parameters and computational method of the SEBS model are reasonably simplified and upswung which is in the environment of the geographical position and present situation in this area in order to more conveniently compute the evapotranspiration with a higher precision.The research on the evaporation estimation in the Yellow River Delta is processed from following six aspects:(1) Analysing and refinement of SEBS model method and theory The basis theory of SEBS model is undersood by reading relevant literatures. Then we analyse the basic theories and computational methods of all parameters in surface energy balance system. While the computational methods are reasonably simplified and upswung which is in the environment of the geographical position and present situation. And on how these simplified or changs could delete some parameters which is less influence on evapotranspiration estimation in this area. As following, the model of evapotranspiration estimation is built on the basic of these simplified computational methods.(2) Implementing SEBS modelThe surface energy balance system model is carried out under windows environment, on the basic of its theory and simplified computational methods by using C# program language. The model function is to meet a demand or requirement of evapotranspiration estimation, accomplishes the computational of all kind of relevant data, analyses the results, and generates thematic maps.(3) Validating the calculationsIn this paper the calculations are validated are in two aspects. First, the computational results in this model are compared with other model in order to check the rationality of analog results. Second, the computational results in this model are compared with others research results, which is to show the reliability.(4) Analysis of temporal-spatial distributionsIn the thesis we have made use of some TM image, which includes the data on May in 2003, 2005, 2007 and on April in 2008, to estimate evapotranspiration in the area of Yellow River Delta. And then a highly perceptive analysis of the calculations is elaborated from the characteristics of time-space distributional and different land use or cover. Analysis showing: the evapotranspiration of this area is considerable influenced by surface water, ground vegetation, wind velocity, solar radiation and human activities. And the distributions of evapotranspiration show a descending tendency from south to north, and a ascending trend from inland area to coastal. And the evapotranspiration in May is higher than April.