中文摘要：

针对甘南草原生态系统水资源压力日益增大及草原退化的形势,本研究采用理论基础坚实、区域应用限制小、反演陆面蒸散发量较为合理准确的SEBS（Surface Energy Balance System）模型。在此基础上,将新一代对地观测数据MODIS应用于反演甘南草原区域地表蒸散发（Evapotranspiration,ET）,并对甘南草原区域7月份的日均ET进行了反演,分析了2000年和2009年间该区域ET的时空分布格局和发展变化。同时,采用图像剖面线分形的方法描述研究区遥感ET的局部以及微观的结构特征,了解遥感ET分布的空间差异和变化趋势。研究表明：该区域日均ET总体上是减少的,其中一些区域变化幅度较大,减少了50%左右;其中,在地表水含量丰富的吉木都塘草原风景区和桑科草原风景区以及西库乎鹿场附近的黄河支流、尕海自然保护区、科才苦河、白龙江、拱坝河及洮河的水体周围,ET量才有7.00mm左右,主要与该区域水资源的减少有关。

英文摘要：

In the context of increasing pressures on water resources and degrading grassland ecosystems in Gannan,this study was aimed at deriving ET across the grassland in Gannan using the Surface Energy Balance System（SEBS） model capable of being applied to large areas in conjunction with Moderate-resolution Imaging Spectroradiometer（MODIS） data produces.Specifically,the daily ET in July of the grassland was estimated,with analyzing the temporal and spatial distributions and changes in ET during the period 2000-2009.Meanwhile,the authors employed the fractal cross-hatching of image method to describe the remotely sensed ET and its distribution characteristics over the study area so as to gain a greater understanding of the differences in spatial distribution and changing trends in ET.The results of the fractal calculation indicated a fractal number of cross-hatching of 1.237 in 2000 and 1.337 in 2009.Marked variations in the profile curve in 2009 indicated a large gradient of ET,whereas a smaller gradient in spatial variation in ET occurred in 2000.Essential factors affecting ET distribution are the patch size of various landscapes,and the number and the combination of space.In particular,the uniformity degree of the distribution in landscapes plays a crucial role in the fractal number of ET.Results also show that as a whole,the average daily ET showed a decreasing trend,with a relatively larger change found in the Bailongjiang to Wubaixiang in Zhouqu County,where the magnitude of decrease was approximately 50%.There was,however,only 7 mm ET occurring over areas which had been sufficient in water resources and expected to show large ET rates,including imudoutang and Sangke grassland scenic pond,peaceful deer farm near the west bank of the Yellow River tributaries,the Gahai Nature Reserve,Branch was bitter River,Bailongjiang,the Dam River,and the Taohe River.This might be related to decreased water resources over these areas.It was also found that the discrepancy between the simulations and the observations were a