中文摘要：

本研究首先对当今常用的冻土模式进行了改进。以土壤总焓和土壤水总质量替代原来的温度和体积水含量作为方程预报量，使冰水相变速率项变为诊断量，避免了原冻土模式计算过程中由于冰水相变速率项预估的误差造成计算过程中的温度偏差。同时对该新形式模式所发展的诊断量方程组设计了合理省时的数值计算方案。实验表明，改进后模式的模拟结果与观测值有较好的吻合。此外，分析比较了目前常用的3种冻融方案的理论基础及模拟结果，发现基于热力学平衡态推导得到的包含土壤水势影响的参数化方案能很好地模拟土壤的冻融变化过程，不同的冻融方案会对土壤内的温度、水量及表面的感热和潜热模拟结果产生较大的影响。

英文摘要：

In this paper,firstly, new version of frozen soil model is presented, in which the enthalpy and total volumetric water equivalent content in soil is used as predictive variables to replace the predictive variables of soil temperature and volumetric liquid water content in the current models respectively. It makes the required estimation of liquid-ice phase change rate in the current models unnecessary, and therefore avoids the introduction of the error in estimation of the phase change rate into the new model and in turn will improve the new version model in both speeding convergence of numerical iterative process and enhancing the model performance. At the same time, a nu- merical scheme is also developed for the diagnostic equations in the new version, which is very efficient for finding the true solution with a few iteration times. It＇s proved the numerical simulation results of the new version model are in good agreement with two field observed data. Besides, based on analyzing three schemes for soil freezing-thaw from theoretical view and comparing the numerical simulation results, it is found that the parameterization scheme, which takes the relation between moisture potential and temperature in soil derived from the equilibrium thermodynamics theory into consideration, can describe the freezing-thaw processes well. Numerical results have shown that different freezing-thaw parameterizations have greater influence on simulated soil temperature, water content, and latent and sensible heat fluxes at soil surface .