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西北干旱、半干旱地区,浅层包气带水分通量主要由水汽组成,而水汽在运移过程中产生的能量转换和质量迁移是地表质能平衡计算不可缺少的重要源汇项。在野外进行一个沙坑实验,发现土壤水在中午(12:00—15:00)达到最大值(10cm深度,5.9~6.1cm3/cm3;30cm深度,11.9~13.1cm3/cm3),而在凌晨(02:00—05:00)出现最小值(10cm深度,4.4~4.5cm3/cm3;30cm深度,10.4~10.8cm3/cm3)。为进一步验证该实验条件下的土壤水运移及分布规律,考虑了土壤水、汽、热耦合运移的HYDRUS-1D模型被用来对实验过程进行模拟,模拟结果与实测结果吻合较好。为描述土壤水分昼夜运移模式,笔者将土壤水耦合运移的时间信息和空间信息进行同步分析;并根据土壤水运移的不同驱动力,分别对温度梯度、基质势梯度作用下的液态水及汽态水通量进行了分析。
In the arid and semiarid regions of Northwest China, the flux of water in the shallow aeration zone is mainly composed of water vapor. The energy conversion and mass transfer during water vapor transport are important sources and sinks for the calculation of surface mass balance. A sand pit experiment was conducted in the field and found that soil water reached its maximum at noon (12: 00-15: 00) (10 cm depth, 5.9-6.1 cm3 / cm3; 30 cm depth, 11.9-13.1 cm3 / cm3) (02: 00-05: 00) appears the minimum value (10cm depth, 4.4 ~ 4.5cm3 / cm3; 30cm depth, 10.4 ~ 10.8cm3 / cm3). In order to further verify the soil water transport and distribution under the experimental conditions, the HYDRUS-1D model considering the coupling of soil water, steam and heat is used to simulate the experimental process. The simulation results are in good agreement with the measured results. In order to describe the diurnal and seasonal patterns of soil moisture movement, the author analyzed the temporal and spatial information of soil-water coupling and migration. According to the different driving forces of soil water transport, the author analyzed the effects of temperature gradient, Steam water flux was analyzed.