Research On Potential Evaportranspiration Changes Of XinJiang

Because of the inner situation of Eurasia, the special topography, atmospheric and solar radiation result the typical temperate continental climate.Wtih the rapidly increasing of population,agriculture and industrym, the water demand rised as well,which worsen the imbalance between supply and demand.The precisely estimation of evapotranspiration plays a practical role in the exploitaion of water resource, the formulation of irrigation programme and the restoration of the natural vegetation. Therefore, this paper aims to estabalish a ET model, which based on the high resolution images and long–term weather data.The model is computed with ArcGIS software.The process will help the fully understand of temporal and spatial variation.a. The Penman-Monteith model is used to calculat the potential evapotranspiration of the 54 stations in Xinjiang. The annual evapotranspiration can be divided into three intensity classes and four time slice, which the intense, middle and weak evapotranspiration. Also, the relationship between the annual potential evapotranspiration and climatic factor was analyzed.b. Satandized by the results of Penman-Monteith model,the results of the revised Penman model,Priestley-Taylor model, Hargreaves-Samani model and 1948 Penman model were analyzed and the error analysis was made.c. Based on ten minutes time frequency weather data, the Penman-Monteith model and Lascano-VanBavel ET algorithm were used on the computation of hourly evapotranspiration. d. With the SPOT-NDVI data, the annual ET-NDVI model is established, the independent variable is accumulated NDVI. The error analysis shows that, the model is good for the computation in North of Xinjiang and in Tianshan mountains, while it makes bigger mistaks in South of Xinjiang.e. The partition function is used to decide the fractural structure of annula evapotranspiration temporal series, the results showed that the annual evapotranspiration temporal series is a single fractural structure, which means that it can be analyzed with R/S on the trendency. The R/S analysis tells that the Hurst exponet of Sorth of Xinjiang, North of Xinjiang and Tianshan mountains from 1955 to 2008 are 0.8960, 0.7194, 0.7889, specificly. That means the three regions that show a markable Hurst, that is to say, the evapotranspiration change persistently. And the South of Xinjiang persistently strongly and Tianshan moutains persistently commonly, and the North of Xinjiang is the last one.