长江源区蒸散量变化规律及其影响因素

The Variation of Evapotraspiration and the Impacts on It in the Source Region of the Yangtze River

利用空间分辨率为1 100 m的NOAA遥感数据,运用表面能量平衡系统(SEBS)模型,结合当地气象站实际观测数据,计算了1991-2001年长江源区的蒸散量,运用线性回归的方法计算了源区各像素点的蒸散量变化趋势,统计分析了蒸散量的多年变化规律。运用地理信息系统技术分析了气温、地表温度、降水量和植被指数(NDVI)等主要因素对蒸散量变化的影响。研究结果表明,源区蒸散量以6.8 mm/a的速度增加。全球变暖引起的气温、地表温度的升高是蒸散量增加的主要原因;在空间分布上,河流左岸阳坡蒸散量增加,右岸阴坡蒸散量减小;降水量、植被覆盖度分别与蒸散量有很好的正相关关系,源区东南部降水量大,植被相对旺盛,蒸腾作用强烈,蒸散量大;西北部降水量小,植被生长稀疏,蒸散量较小。

The source region of the Yangtze River has experienced eco-hydrology deterioration in lastest 2 to 3 decades.To analyse the region hydrological variations,exploit Surface Energy Balance System（SEBS）,based on NOAA remote sensing data,and the meteorological data provided by local meteorological stations,we calculated the annual evapotranspiration（ET） in the source region of the Yangtze River from 1991 to 2001.Employing linear regression method to count the evapotranspiration trends in every pixel,we analysed the inter-annual variation of evapotranspiration spatially.Using Geographic Information System,the impacts of temperature,surface land temperature,precipitation and NDVI（vegetation index） on evapotranspiration variation have been assessed.The results show that evapotraspiration increases at the speed of 6.8 mm/a.The rising temperatures with the Global Warming are the main factors to lead to the inter-annual evapotraspiration increasing in the lastest two decades.In space,evapotranspiration increases at the left bank of the Yangtze River,which is sunny aspect,while the evapotranspiration decreases at the right bank of the river,back sides of the mountains.Precipitation and vegetation coverage have a good positive correlation with evapotranspiration respectively.Evapotranspiration in the southeast of the region with large rainfall and relatively dense vegetation is larger than that in the northwest of the region with small rainfall and sparse vegetation.Findings of this study may be significant for finding out relationship between water resources and climate changes.