应用EOS/MODIS卫星资料反演与估算西北雨养农业区地表能量和蒸散量

应用定西地区的陆面过程野外观测资料和四次EOS_MODIS卫星资料，对典型的西北半干旱雨养农业区的基本地表特征参数进行反演，在此基础上对各能量通量和蒸散量进行估算，进而分别分析其季节和空间变化.结果表明：应用卫星数据估算的各参量的相对误差基本都在20%以内，其空间和时间变化基本反映了当地的实际情况；区域各通量和日蒸散量分布极不均匀，表现为四季相差比较大的单峰型变化特征，冬季最小、其次是秋季、夏春两季最大；与面积较大的中、低植被覆盖度区域相比，小范围的高植被覆盖度区域的地表净辐射、潜热和日蒸散量相对较高，土壤热通量和显热通量相对较低，并且都在春、夏季节表现得更加显著.低、中植被覆盖度区的各能量通量的季节变化不显著的特征反映了半干旱西北雨养农业区土壤的干土层相对比较厚的特征.

Estimation of surface energy and day evapotranspiration in a dry-farming region of Northwest China using satellite data

By using observational data of land processes and EOS/MODIS data,the surface parameters,energy flux and day evapotranspiration in the dry-farming region in Northwest China are derived.Then,the spatial-temporal variety of flux and day evapotranspiration are analyzed.The result shows that surface characters of the region are well reflected by retrieval values from EOS/MODIS.The most of relative errors of different parameters are less than 20%.There are asymmetric distributions of flux and day evapotranspiration of the region.The current of seasonal change is of a single-apex model,which is lower in winter and higher in summer.Comparing with the region with middle and low vegetation fractions,the values of some parameters are higher for the region with a higher vegetation fraction,which include net radiation,latent heat flux and day evapotranspiration.The values of other parameters are lower which are soil heat flux and sensible heat flux.The characters of all these parameters are more prominent in spring and summer.Seasonal change of energy flux in middle and low vegetation fraction regions is not obvious,showing that dry soil is thick in the dry-farming region in Northwest China.