Impacts of Land Surface Hydrological Parameterizations on Terrestrial Carbon Flux Simulation

The soil water is one important controlling factor to the carbon assimilation process of the terrestrial vegetation, and the reasonable description of land surface hydrological cycle is crucial to the accurate estimation of the carbon flux between vegetation and atmosphere. By using Global Soil Wetness Project (GSWP-2) near surface meteorological dataset, several global simulation are carried out to evaluate the possible impacts of different land surface hydrological schemes on the terrestrial carbon flux simulation by using NCAR Community Land Model version 3.0 (NCAR CLM3.0). Results show that the original scheme of NCAR CLM3.0 gives too much leaf interception as well as too large surface runoff. As a result, it produces too dry soil and thus too smaller carbon assimilation over most tropical regions, especially in the dry season. In contrast, all the other three schemes (NY Scheme, Niu et al. 2005; RD scheme, Dickinson 2005; CoLM scheme, Dai 2005) substantially improved the representation of the land surface hydrological cycle. The decreased leaf interception and surface runoff produces wetter soil and larger carbon assimilation over most tropical regions, especially in the dry season.