Numerical Simulation on Climate Effects of Freezing-Thawing Processes Using CCM3

A parameterization of soil freezing-thawing physics for use in the land-surface model of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) is developed and evaluated. The new parameterization scheme has improved the representation of physical processes in the existing land surface model. Numerical simulations using CCM3 with improved land-surface processes and with the original land-surface processes are compared against the NCEP reanalysis. It is found that the CCM3 version using the improved land surface model shows significant improvements in simulating precipitation in China during the summer season, the general circulation over East Asia, and wind fields over the Tibet Plateau. For the summer season, the improved model was able to better simulate the Indian summer monsoon components, including the mean northerly wind in the upper troposphere and mean southerly wind in the lower troposphere.