基于地面试验的土壤表面阻抗估算研究

Estimation of Soil Surface Resistance Based on Field Experiment

基于地面试验,利用土壤蒸发计算公式求算土壤水汽阻力的反推法,论文对土壤表面阻抗进行了估算,并研究了土壤表面阻抗与土壤含水量之间的关系。反推法所需参数土壤蒸发量由称重法获得,空气实际水汽压由观测的相对湿度和空气温度数据计算而得,土壤表面饱和水汽压由观测的土壤表面温度计算而得,空气动力学阻抗由观测的涡度相关数据计算而得。研究结果表明,土壤表面阻抗与土壤质量含水量之间存在较好的指数函数关系,即土壤表面阻抗随土壤质量含水量的增加呈指数函数递减,由此说明通过土壤含水量计算土壤表面阻抗是一种新的可行途径。另外,在计算过程中也发现空气动力学阻抗的准确计算是应用反推法获取土壤表面阻抗的最关键因素,也是给此方法带来不确定性最大的因素,较大的空气动力学阻抗误差甚至会使土壤表面阻抗出现负值。

Based on the field experimental data, soil surface resistance was deduced from the the- oretical formula of soil evaporation and the relationship between soil surface resistance and soil wa- ter content was studied in the paper. Soil evaporation obtained by weighing method, air vapor pressure calculated from relative humidity and air temperature, soil surface saturation vapor pres- sure calculated from soil surface temperature and aerodynamic resistance obtained by eddy covari- ance method were used to calculate soil surface resistance. The results showed that there is an ob- vious exponential function between soil surface resistance and soil water content, namely soil sur- face resistance exponentially declines with the increase of soil water content, which provides an alternative way of computing soil surface resistance. It should be noted that aerodynamic resist- ance is the key parameter in the calculation of soil surface resistance. In the study, aerodynamic resistance is derived from the formula of surface sensible heat flux. The error of aerodynamic re- sistance may even cause negative soil surface resistance value. The accuracy of soil surface resist- ance is determined by aerodynamic resistance to some extent.