LAS在西北干旱区荒漠均匀下垫面的观测研究

Observation Study in Desert Homogeneous of Arid Region in Northwestern of China Using Large Aperture Scintillometers

利用"古浪非均匀近地层观测试验"的仪器平行对比观测部分试验数据,首先分析荒漠均匀下垫面大孔径闪烁仪(Large Aperture Scintillometer,LAS)光径线上等间距架设的4台涡动相关仪(EddyCovariance System,EC)观测的摩擦速度和感热通量的一致性。然后,基于4种不同下垫面建立稳定度普适函数分析,利用4台EC观测摩擦速度平均值,计算了LAS观测区域的感热通量,进而比较了LAS和EC两者观测值的差异。结果表明,4台EC观测的摩擦速度与感热通量一致性好,摩擦速度的差别<10%,感热通量的差别在10%左右。4种稳定度普适函数计算的LAS区域感热通量在白天、夜晚与EC观测平均值变化趋势一致,但计算值偏大;TAG(Thiermann and Grassl)稳定度普适函数计算值与EC观测平均值较接近。其主要原因除不同下垫面试验所得稳定度普适函数的差异外,Kipp&Zonen LAS所测感热通量的系统性偏高不可忽视。

Using the experimental data that came from the instrument parallel comparison in Gulang Heterogeneous Underlying Surface Layer Experiment, the consistency of friction velocity and sensible heat flux observed by four sets of EC （Eddy Covariance System） which equidistantly lay on light path line of LAS （Large Aperture Scintillometer） was analyzed at first, and then the difference among the calculat- ed regional sensible heat fluxs observed by LAS based on universal stability functions established by four different kinds of underlying surface employing the mean value of observation friction velocity from four sets of EC was analyzed, finally a further comparison between the two observations of LAS and EC was made. The results show that, friction velocity and sensible heat flux observed by four sets of EC have a good trend of consistency; the difference of friction velocity is less than 10~, and the difference of sensible heat flux is about 10%. The regional sensible heat flux of LAS calculated by four kinds of universal stabili- ty functions in the daytime and nighttime have identical changing trend with the average observed by EC, the calculated value is usually bigger than normal, the calculated value of TAG universal stability function is closer to the average value observed by EC. Except for the main reason that universal stability functions from experiments of different underlying surface have some differences, the sensible heat flux observed by Kipp＆Zonen LAS is systemic higher can not be ignored too.