CLM3.0模式中冻土过程参数化的改进及模拟试验

Improvement and Validation of the Frozen Soil Parameterization Scheme Used in NCAR CLM3.0 Model

对NCAR CLM3.0(Community Land Model)的冻土过程参数化进行了改进。根据平衡态的热力学关系和考虑含冰量的土壤基质势的经验公式定义了冰点下的最大液态水含量,超过最大液态水含量的部分冻结为冰,并在水导率的计算中加入了冰的阻挡作用。利用青藏高原改则站2003年4月1日至2004年12月31日的观测资料进行了单点模拟试验,模拟结果表明,原模式对辐射通量模拟比较准确,但低估了冬季冻结期的液态水含量,高估了冰含量,土壤温度也因此出现偏差,改进冻土参数化后对液态水和冰的模拟明显改善,土壤温度模拟也更接近实测,部分改进了模式对土壤水热过程的模拟能力。

A frozen soil parameterization scheme is developed based on the NCAR CLM3.0（Community Land Model）.Using the equilibrium thermodynamic relationship and the empirical equation considering the effect of ice on the matrix potential,the authors define the maximum liquid water content below the freezing point temperature and take account of the resistance of ice to hydraulic conductivity.Only when the liquid water exceeds the maximum,it freezes to ice.Both the original and modified scheme are tested using the observations of Gaize station on the Tibetan Plateau from April 2003 to December 2004.Results show that the original model can perform a good prediction of the radiation flux,but underestimates the liquid water content,and overestimates the ice content in winter,so soil temperature bias has thus occurred.The modified scheme obviously improves the estimation of soil liquid water and ice content,and the simulated soil temperature is closer to the observation.Thus it partly improves the simulation performance of CLM3.0 on frozen soil processes.