HR: 0800h
AN: B41B-0456    [Abstracts]
TI: Climate Impacts of Potential Vegetation versus Current Day MODIS Land Cover in the Community Climate System Model (CCSM)
AU: * Lawrence, P J
EM: Peter.J.Lawrence@colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences (CIRES), Campus Box 216, University of Colorado, Boulder, CO 80309, United States
AU: Chase, T N
EM: tchase@cires.colorado.edu
AF: Cooperative Institute for Research in Environmental Sciences (CIRES), Campus Box 216, University of Colorado, Boulder, CO 80309, United States
AB: Numerous studies have used General Circulation Models to investigate the possible climate impacts that human development has had through transforming the world from natural ecosystems to one dominated by cultivation, grazing, pastures and urban landscapes. In recent climate sensitivity studies we have found that the global representation of vegetation and soils, as well as the surface hydrology in the Community Land Model (CLM) has large impacts on the climate simulated in the Community Climate System Model (CCSM). Therefore to investigate the climate impacts of land cover change in CCSM we have developed new potential vegetation land surface parameters for CLM that are consistent with our current day MODIS land surface parameters. The new parameters use the potential vegetation biome mapping of Ramankutty and Foley, (1999), with the spatial heterogeneity and temporal phenology of plant functional types (PFTs) extrapolated from the MODIS parameters of current day remnant natural biomes. The potential vegetation parameters replace land use, predominantly cropping, with natural tree, shrub and grass PFTs, resulting in substantially higher leaf area index (LAI) and stem area index (SAI) over much of the world. The climate impacts of the potential vegetation parameters are assessed through climate sensitivity studies with the CCSM compared to the climate simulated with the current day MODIS parameters. The main impact of the potential vegetation on the climate simulated in CCSM is an overall cooling from increased latent heat flux, with mixed impacts from albedo changes. This is consistent with previous GCM studies where surface hydrology dominates the forcing from land cover change, but is opposite to studies where the surface albedo is the dominate change. The strong dominance of surface hydrology in changes with the potential vegetation parameters underscores the importance of providing realistic hydrology and land cover in CCSM sensitivity experiments.
UR: http://cires.colorado.edu/science/groups/chase/people/lawrence/
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0429 Climate dynamics (1620)
DE: 0430 Computational methods and data processing
SC: Biogeosciences [B]
MN: 2007 Fall Meeting