黄土高原における土壌水分と熱収支 : 土壌3層モデル内のパラメーターの決定とモデル計算の結果 Soil Water Content and Heat Balance in the Loess Plateau : Determination of Parameters in the Three-Layered Soil Model and Experimental Result of Model Calculation
Parameters used for a three-layered soil model are determined for the purpose of understanding the soil water content and heat balance on the Loess Plateau, China. The soil types on the Loess Plateau are divided into heavy loam, medium loam, light loam, sandy loam and sand. The soil water potential and the surface albedo are parameterized as the function of soil water content. The diffusion distance of water vapor that decides the evaporation efficiency can be simulated by using the saturated volumetric soil water content, field capacity of soil water content, wilting point and maximum value of the diffusion distance, even if the soil types are different.<br>The model calculation is verified by comparing the observed results. The calculated results of the soil water content and evaporation coincide with the values observed by gravimetric sampling and lysimeter. According to the results observed by the column experiment, the model calculation represents the qualitative difference of evaporation due to the soil texture.<br>Seasonal variation of the soil water content is simulated by using the actual meteorological data for the Loess Plateau. The soil on the Loess Plateau was generally superior from the viewpoint of the maintenance ability of moisture. It is found that the fractional extractable water calculated by the soil water content can be an index to classify the present state of vegetation cover such as forest, shrub, grassland or desert.
農業気象 60(1), 55-65, 2004-03-10