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

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.