一种非饱和土表层蒸发过程的预测方法

探索了一种由土壤基本物性指标、气象数据预测非饱和土表层蒸发过程的方法。通过土壤基本物理性质（颗粒分布、土粒相对密度、干密度）预测出土-水特征曲线（SWCC），进而得到土壤气相对湿度与含水率的关系，采用Penman-Wilson模型预测出了非饱和土表面的蒸发曲线。通过该方法，只需实地采取土样，获取其基本物理性质，由任意时刻土壤的含水率及气象数据就能预测出该时刻土表的蒸发速率。采用自制的自动蒸发测量系统进行浅层土蒸发试验，得到了蒸发曲线，与预测结果进行比较发现预测蒸发过程与实测结果一样皆由临界含水率和风干含水率将其分为3个阶段：稳定阶段、减速阶段和残余阶段，且蒸发量吻合，证明了所提出方法的准确性和实用性，对工程界估计土表蒸发量，确定水流量边界有重要意义。

A method for predicting evaporation process in unsaturated soil surface

A method for predicting evaporation process in unsaturated soil surface is presented based on physical properties of soil and meteorological data. The soil-water characteristic curve (SWCC) is estimated by physical properties of soil (i.e. particle size distribution, specific gravity and dry density). Then, the relationship between relative humidity of soil surface and water content is obtained based on the SWCC. Finally, the Penman-Wilson model is applied to predict evaporation curve of unsaturated soil surface. In this method, only in situ soil physical properties and meteorological data are needed to get the predicted evaporation curve. The evaporation rate of soil surface can be obtained with given water content at that time. Laboratory evaporation tests of thin layer soils are conducted in a designed evaporation measuring system. The measured evaporation curves are compared with those predicted. The results show that the measured and prediction evaporation curves have same processes and slight difference in evaporation rate. Three evaporation stages, i.e. stable rate stage, reducing rate stage and residual stage, are evidently shown in both observed and predicted curves. The stages are divided by as called critical moisture content and air-dried moisture content. The suggested method is accurate and practical for engineers to predict unsaturated soil surface evaporation rate and determine the boundary flux.