基于冠层顶端水面蒸发估算水稻蒸腾蒸发量及冠层下土面蒸发

Calculations of Crop Evapotranspiration of Rice and Soil Evaporation Beneath Rice Canopy Based on Water Surface Evaporation of Canopy Top

改进FAO-56推荐作物系数模型,用易于观测的冠层顶端水面蒸发(Epan)代替参考作物蒸腾蒸发(ET0),采用作物生长指标(叶面积指数)确定作物系数及冠层下土面蒸发系数;根据波文比能量平衡法及Lysimeter实测作物蒸腾蒸发量(ETc)及冠层下土面蒸发(Eg,稻田为冠层下水面蒸发),检验模型准确性。结果表明,基于Epan确定的作物系数(Kc pan)与FAO推荐值虽有较大差异,但可以用于估算ETc,作为田间灌水指导依据。另外,新增Eg计算模块,应用叶面积指数模拟土面蒸发系数(Ke)的动态变化,实现了作物蒸腾及土面蒸发的分离预测。

Crop coefficient method of estimating evapotranspiration （ETc） recommended by FAO - 56 was revised through using water surface evaporation of canopy top （Epan） instead of reference evapotranspiration （ETo）, and applying the leaf area index to determine crop coefficient and soil evaporation coefficient. The revised model was verified by comparing the measured ETc and fitted values using Bowen Ratio Energy Balance method. The results showed that Epan could be used to estimate ETc, though there was a relative larger difference between crop coefficient based on Epan and crop coefficient by FAO. The new calculation module of soil evaporation beneath the rice canopy and the dynamic change of soil evaporation coefficient fitted by leaf area index realized the separating predictions of crop evaporation and soil evaporation.