干旱区农田下垫面kB^(-1)变化特征及参数化

Change characteristics and parameterization of kB^(-1) over arid farmland surface

利用古浪非均匀近地层观测试验中农田下垫面的湍流观测数据,计算了其附加阻尼k B-1,并对其变化特征进行了分析,之后通过对k B-1影响因子的分析,发展了一种适用于干旱区农田下垫面的k B-1参数化方案W14,最后对W14在平坦戈壁下垫面上的适用性进行了检验.结果表明:农田下垫面k B-1日均值随着叶面积指数的增大有线性减小的趋势,k B-1的日变化随着叶面积指数的增大而变得更加明显.k B-1受地表特征叶面积指数、动力学因子Re*和热力学因子θs-θa的综合影响.基于这些影响因子所发展的W14在干旱区农田下垫面上计算的感热通量精度高,优于已有参数化方案的计算精度.并且W14在平坦戈壁下垫面也有一定的适用性.

Based on the turbulence data observed in the Gulang heterogeneous underlying surface layer experiment, kB^-1 value of the farmland surface was calculated and the characteristics of kB^-1 were analyzed. A new parameteriza- tion of kB^-1 called W14 was proposed through the kB^-1＇s impact factor analysis. The applicability of W14 was tested in the flat Gobi surface. The results showeded that the daily average kB^-1 value tended to decrease linearly with an increased leaf area index（LAI）; the diurnal variation of kB^-1 became more significant with an increase of LAI. kB^-1 was comprehensively influenced by the surface feature LAI, dynamic factor（Re,） and thermodynamic factor（θs -θa）. W14 scheme which was developed on the basis of these influence factors has high precision in estimating sensible heat flux over farmland surface in arid region, and it is better than other tested schemes. And it can also be applied to the flat Gobi surface.