陆面过程模式对不同土壤物理性质的敏感性研究

The Sensitivity of Land Surface Model to Physical Properties of Different Soils

使用NCAR陆面过程模式 (LSM)和荷兰Cabauw 1987年的大气观测资料 ,考察了在 11种不同的土壤条件下陆面过程模式所模拟的地表能量及水分循环的差异 .结果表明 ,粘土含量较高的土壤具有较好的持水能力 ,蒸发量和径流量都比较大 ,而在含砂量高的土壤中 ,水分大量的下渗 ,蒸发量和径流量小 ,从而影响到地表热通量的分配 .在不考虑大气反馈的情况下 ,各种土壤造成的差异主要出现在春季的 4、5月份 .

Using NCAR Land Surface Model (LSM), the Netherlands Cabauw observational atmospheric forcing data are analyzed to study the difference of surface energy and water cycle on different soil types. Every soil type percentages are obtained from midpoint values of each textural class, following the U. S. Department of Agriculture textural triangle. It is found that in land surface model, soil thermal and hydraulic properties, parameterized from Farouki (1981) and Cosby (1984), are much depended on the values of percent sand, silt and clay. It is revealed that the assignments of water and energy are very sensitive to soil conditions. The soils rich in clay, such as clay and silty clay, have well water-content ability and result in more evaporation and more runoff; the soils rich in sand, for its low water potential and high hydraulic conductivity, conduct more water and less evaporation and runoff. The annual mean water content difference of the soil layers is about 0.2 m 3 \5m -3 , the drainage difference of groundwater is about 17%, the maximum difference in evaporation is equivalent to 10% of annual precipitation; the runoff difference is equivalent to 3.53% of annual precipitation. Because of the vegetation coverage is 97%, effect of soil moisture on net radiation is hardly presented. However, in the assignment of surface heat flux, the latent heat flux is the maximum and the sensible heat is the minimum, with the maximum difference in spring. The maximum standard deviation of the sensible heat and the latent heat is about 12 W\5m -2 .