Simulation of Thermal and Hydraulic Properties Affected by Organic and Gravel Soil over the Tibetan Plateau during Summer

The soil of some parts of the Tibetan Plateau contains an abundance of organic matter and gravel. On the basis of previous research, a new parameterization scheme has been developed to consider the influences of these material on soil thermal and hydrological conductivities. Sensitivity experiments conducted by using the Common Land Model to improve the parameterizations of soil temperature, hydraulic conductivities, and soil surface resistance are compared with simulation results from off-line numerical experiments reported by Southeast Tibet and Namco stations. By using the new parameterization scheme, the average deviation of the simulated soil moisture reported by the former station decreased by 0.04; however, the value showed a slight increase above the layer of 20 cm at the latter station. Although the average deviation of soil temperature, except at the surface, is decreased by 0.2℃ at the Southeast Tibet station, the biases decrease above the layer of 40 cm at the Namco station. With the new parameterization, the discrepancies of soil net radiation and surface sensible and latent heat fluxes are reduced. In particular, the surface latent heat flux at the Namco station in July and August is reduced by about 20 W m^-2, which is closer to the observation value than that obtained by using the original parameterization.