几种实际蒸散计算方法在土壤水分模拟中的应用

APPLICATION OF SOME ACTUAL EVAPOTRANSPIRATION MODELS IN SIMULATION OF SOIL MOISTURE

在田间试验的基础上 ,将较为常用的Penman和Priestley Taylor参考蒸散模式的修正模型、实际蒸散模式中常用的密集植被状况下的Penman Menteith模式和稀疏植被状况下的Shuttleworth Wallace模式计算的玉米蒸散结果进行比较 ,并利用不同气候年型的土壤水分观测资料对土壤水分变化进行模拟 ,发现干燥年型几种蒸散模型的模拟效果均好于湿润年型 ,尤其是动力模型。在湿润年份Penman修正模型的模拟效果好于Priestley Taylor修正模型 ;在干燥年份玉米旺盛生长季Shuttleworth Wallace模式的拟合效果好于Penman Menteith模式 ;但在湿润年份Penman Menteith模式在叶面积较大时模拟效果较好。相对而言 ,参考蒸散修正模型中含有土壤水分参数 ,对土壤水分变化的模拟较为稳定 ,动力模型中含有参数较多 ,并非全部实测 ,因而在玉米生长量较小、表面干湿状况变化较大时模拟的稳定性较差。模拟结果表明 ,使用环境要素模拟土壤水分变化在一定时间长度内效果较好 ,时间过长可造成较大的累积误差。

Based on experiments in the field, a comparison of modified referenced evapotranspiration model such as Penman model and Priestley Taylor model, actual evapotranspiration model such as Penmen Menteithin model for closed canopy and Shuttleworth Wallace model for sparse canopy is made. Observed data of soil moisture in two years of different climatic patterns is used to simulate the variation of soil moisture. The results show that in dry years the fitness of four models is better than that in rainy years, especially for dynamical models. In rainy years, when maize plants fully grow, the fitness of Shuttleworth Wallace model is better than that of Penman Menteith model, but in dry years when leaf area is bigger, the fitness of Penman model is better. Comparatively, fitness of modified referenced evapotranspiration models is stable owing to those models including parameters of soil moisture. There are many parameters in dynamical models among which some parameters are not observed. Therefore, when maize plant is small and the moisture content in surfaces of both leaves and soil varied frequently, the fitness of dynamical models is unstable. The results also show that the fitness of variation of soil moisture content simulated by using environmental factors is reasonable in a certain time scale and a big accumulated error will appear on a long time scale over one month.