This presentation will address the following key questions, using the fully coupled global atmosphere-ocean-land model, NCAR CCSM3.5, with dynamic vegetation.
How well does CCSM3.5 simulate monsoon dynamics across North America?
How well does CCSM3.5 simulate vegetation patterns across North America?
How does vegetation affect climate in the North American monsoon region?
How do vegetation feedbacks over the North American monsoon region compare with those across the other global monsoon regions?
In order to assess vegetation feedbacks, initial value ensemble experiments are performed in which vegetation cover fraction is reduced by 0.2 over the North American monsoon region (and other global monsoon regions) and the climatic response is determined.
Results/Conclusions CCSM3.5 produces a reasonable seasonal onset of the global monsoons, although they are generally too strong and sometimes penetrate too far inland; this is likewise true with the North American monsoon. The model captures the global distribution of major biomes, although it oversimulates vegetation cover and has gaps in the boreal forests and Amazon rainforest. Over the United States, CCSM3.5 simulates evergreen forests in the Southeast, deciduous forests in the Northeast, and herbaceous plants in the West, similar to observed. Over the global monsoons, including the North American monsoon, reduced vegetation cover results in less sensible and latent heat fluxes, higher temperatures, and diminished precipitable water. The feedbacks over the North American monsoon are generally more thermal in nature, rather than hydrological.