Modeling of Vegetated Surface Processes and Climate-Carbon Interactions

 A current major thrust of vegetated surface modeling as part of climate-carbon interactions is to better assimilate carbon into their terrestrial systems through modeled leaves, allocate the carbon between various reservoirs, and transform this stored carbon into other forms, with consequent leaf metabolic processes which ties to dynamics of ecosystems and biogeochemical cycling. Climate variables determine the initial rates of carbon assimilation, the rates of the internal transformations and release back to the atmosphere, which are directly linked to the dynamics of vegetation.

 Our recent study has found significant temperature and precipitation biases of standard CLM (NCAR Community Land Model) simulations compared with observations (Dickinson et al., 2006). The modeled tropical hydrological cycle is unrealistic shown as too low precipitation over the wet season and too warm during the dry season over the Amazon basin, while high latitudes of northern winter are biased sufficiently warm and summers are too cold. These model deficiencies could have a significant impact on the simulated global land temperature and precipitation and thus carbon cycling because both the tropics and high latitude lands are vulnerable carbon pools.

 We also found that the modeling of the canopy light environment as implemented in current CLM is seriously deficient in its partitioning of light between vegetation canopies and underlying surfaces due to its unrealistic assumption of plane parallel canopy geometry, in particular for the semiarid systems with sparse shrubs, and northern forest with winter snow-pack. This consequently leads to the underestimation of the light loading on the canopy, and hence its carbon assimilation.

 We have been developing a more realistic three dimensional canopy radiation model for climate modeling to describe the canopy geometric (shadow) effect to improve the model climate simulations and energy partitioning between canopy and its underlying surface. For details about 3D canopy radiation model, click here