关键词: 冠层表面阻力, 蒸散, 环境因子, 拟合模型

Abstract: Surface resistance takes an important role in vegetation-atmosphere interaction. A model simulating the relationship between canopy surface resistance and environmental factors is established. According to one data set of Bowen ratio-energy balance above winter wheat canopy observed in 1992 in North China Plain, four parameters in the model are fitted by multi-variable nonlinear least-square optimum algorithm. The updated relationship between surface resistance and such environmental factors as solar radiation, air temperature, saturated vapour pressure deficit and soil moisture in root layer is obtained. The model is validated with other two data sets acquired in 1992 and 1995 for predicting canopy surface resistance. It is shown that the model is capable of modeling canopy surface resistance over the main growth stage of winter wheat with agreement index of 0.93 and 0.67, respectively. When the model is applied to Penman-Monteith formula, it is shown that the estimated evapotranspiration agrees well with that observed from field. The agreement index of evapotranspiration is over 0.90 and the mean bias is less than 5%. The evapotranspiration predicted by the model is closer to the observed with Bowen ratio-energy balance method than that by aerodynamics resistance method. The results of sensitivity analysis show that when four parameters change ±20%, the corresponding changes of evapotranspiration are different. The changes caused by the parameters related to saturated vapour pressure deficit and soil moisture are more obvious than those caused by the parameters related to solar radiation and air tempreture. Saturated vapour pressure deficit and soil moisture are shown the major factors affecting the evapotranspiration rate and canopy surface resistance. The influence of the parameters on evaporation depends on how much the environmental factors are.

Key words: canopy surface resistance, evapotranspiration, environmental factors, model