基于集合卡尔曼滤波和通用陆面模型(CLM1.0)发展了一个地表温度的同化系统。这个系统同化了MODIS温度产品,并将MODIS的叶面积指数引入CLM模型中,主要用于改进地表水热通量的估算精度。将CLM输出的地表温度与MODIS地表温度建立关系,并作为同化系统的观测算子。将MODIS地表温度与实测地表温度进行了比较,将其均方差(Root Mean Square Error,RMSE)作为观测误差。选取3个美国通量网站点(Blackhill、Bondville、Brookings)作为实验数据,结果表明:同化结果中地表温度、显热通量的估算精度均有提高。其中Blackhill站的估算精度改进最大,均方差由81.5W·m-2减小到58.4W·m-2,Bondville站均方差由47.0W·m-2减小到31.8W·m-2,Brookings站均方差由46.5W·m-2减小到45.1W·m-2。潜热通量估算精度在Bondville站均方差由88.6W·m-2减小到57.7W·m-2,Blackhill站均方差由53.4W·m-2减小到47.2W·m-2。总之,结合陆面过程模型同化MODIS温度产品估算地表水热通量是可行的。
Aerodynamic roughness length （Z0m） is a key factor in surface flux estimations with remote sensing algorithms and/or land surface models. This paper calculates ZOrn over several land surfaces, with 3 years of experimental data from Xiaotangshan. The results show that Z0m is direction-dependent, mainly due to the heterogeneity of the size and spatial distribution of the roughness elements inside the source area along different wind directions. Furthermore, a heuristic parameterization of the aerodynamic roughness length for heterogeneous surfaces is proposed. Individual Z0m over each surface component （patch） is calculated firstly with the characteristic parameters of the roughness elements （vegetation height, leaf area index, etc.）, then Z0m over the whole experimental field is aggregated, using the footprint weighting method.
