非均匀下垫面湍流通量观测的印痕分析

Footprint Analysis of Turbulent Flux Measurement over Heterogeneous Surface

利用2005年在北京昌平区小汤山开展的非均匀下垫面观测实验的观测数据,分别处理了涡旋相关法和大孔径闪烁仪LAS测得的感热通量,并运用印痕模型对数据进行"源区"分析。分析结果表明:在复杂地表上,涡旋相关的测量值由于混杂了其他下垫面的通量信息,不能真实地反映其观测区域的湍流特征,存在着观测误差。而LAS观测出现的低估问题则与掺混高度和"源区"有关。通过用印痕方法进行数据订正后,以上问题均得到很好的改善,订正结果与LAS观测通量的线性关系良好,两者的相关系数达到0.9。实验结果验证了印痕模型在非均匀下垫面的适用性。

To test the applicability of the footprint modal over complex surface, heat flux data measured from Beijing Xiao Tang Shan heterogeneous field experiment in May 2005 are used. The data from eddy covariance measurements and Large Aperture Scintillometer （LAS） are processed and analyzed by a footprint model, respectively. Because of heterogeneity, the measurement of eddy covariance method seems to be ambiguous, which contains turbulence information from other land covers. The LAS data have a problem of underestimation due to the blending height and ＇ source area＇ effect. After corrected by the footprint method, they are in good agreement. The results demonstrate that the footprint model is an effective and practical tool to solve the heterogeneous problem in the turbulence flux study.