Simulated impact of vegetation on climate across the North American monsoon region in CCSM3.5

The influence of prescribed changes in vegetation on the climate of the North American monsoon region is examined using the National Center for Atmospheric Research Community Climate System Model Version 3.5 (NCAR CCSM3.5). Initial value ensemble experiments are performed in which the vegetation cover fraction over the North American monsoon region is reduced by 0.2 and the intra-annual climatic response is assessed probabilistically in each one-year ensemble experiment. Changes in the surface radiation budget include decreases in sensible and latent heat fluxes and increases in upward longwave and downward shortwave radiation fluxes, with small net changes in surface albedo. The climatic responses to reduced vegetation cover fraction include year-round increases in ground and surface air temperature, a dampened hydrologic cycle with decreased springtime evaporation, springtime and autumnal precipitation, and autumnal cloud cover, and enhanced atmospheric subsidence in late autumn. Decreased vegetation shifts the monsoon season over the Southwest United States earlier in the year. Within the North American monsoon region, the most robust vegetation feedbacks to climate are found over woody landscapes.