季节性冻融土壤水热耦合运移模拟

SIMULATION OF COUPLING TRANSMISSION OF WATER AND HEAT IN SOIL UNDER SEASONAL FREEZING AND THAWING

根据季节性冻融条件下土壤垂直一维水热运移状况,在地表能量质量平衡条件下,利用水热耦合模型对土壤温度和水分变化进行了模拟。模拟时考虑土壤冻结时冰和水对土壤体积热容、热传导及导水度的影响,并考虑了雪盖层的影响。本模型由实验所在地2008年1月1日至2010年12月31日连续3 a气象数据驱动,用实测地温、水分和冻结深度数据进行验证。结果表明,在地面以下0、5、40、80、160 cm等不同深处模拟温度与实测温度均方根误差(RMSE)分别为3.65、1.59、1.75、1.35、1.64℃,冻结深度也趋一致。除去表层,其他不同深度土壤含水量模拟值与实测值平均误差在3%左右,均方根误差低于4%。此模型及参数化方案能够模拟季节性冻融条件下一定深度土壤温度、水分运移状况,可用于多年冻土区活动层水、热变化规律研究,并可与生态过程模型耦合,从而改进冻土环境下生态系统模型中土壤温度、水分和冻融深度的模拟精度。

Based on vertical one-dimensional water and heat movement in soil under seasonal freezing and thawing, a water-heat coupling model was used to simulate variation of moisture and temperature in soil with surface energy and mass in balance. The simulation took into account the effect of ice and water, at times of freezing, on volumetric heat capacity, heat conduction and hydraulic conductivity and the effect of snow cover on the soil surface as well. The model used the meteorological data collected at the weather stations in the studied area during the three years from Jan. 1, 2008 to Dee. 13, 2010 and was verified with observed data of soil temperature, soil moisture, and depth of freezing. Results show that the simulated and the measured data of soil temperature varied with a root mean square error of 3.65, 1.59, 1.75, 1.35 and 1.64℃ at 0, 0. 05, 0. 40, 0. 80 and 1.60m in depth, respectively. The data of frozen depth was almost identical. And the data of soil moisture differed with a mean error of 3% at all the depths except for the surface, and with a root mean square error （RMSE） of less than 4%. Therefore, it could be concluded that the model presented in this study could be used to simulate water and heat movement within a certain depth of soil under seasonal freezing and thawing. It can also be used to study laws of the variation of soil water-heat in the active layer in the permanent frosted regions. Cou- pled with the ecological process model it will help improve precision of the frozen soil eco-environment model in simulating soil temperature, soil moisture and depth of freezing.