HR: 1340h
AN: B33B-1031    [Abstracts]
TI: Effects of Clouds and Aerosols on Vegetation - Atmosphere Flux Exchanges
AU: * Gu, L
EM: lianhong-gu@ornl.gov
AF: Oak Ridge National Lab, Buiding 1509-6335, Oak Ridge, TN 37831 United States
AU: Liu, Q
EM: l8u@ornl.gov
AF: Oak Ridge National Lab, Buiding 1509-6335, Oak Ridge, TN 37831 United States
AB: The presence of clouds and aerosols in the sky brings change to almost every meteorological variable that drives terrestrial carbon and hydrological cycles. Clouds and aerosols strongly modulate both the quantity and quality (spectrum / diffuse / direct beam) of surface solar radiation as well as longwave radiation, temperature, humidity, and soil moisture conditions. They also introduce extra spatial and temporal scales in addition to those related to topography and diurnal and seasonal cycles. These cloud/aerosol-induced meteorological changes affect carbon dioxide assimilation, soil organic matter decomposition, transpiration, and physical evaporation. They also alter the coupling between photosynthesis and transpiration and the partitioning of available energy. The alteration of surface energy partitioning modifies the properties of atmospheric boundary layer and influences the physical processes in which clouds and aerosols are involved, thus effectively forming a feedback loop in the atmosphere-biosphere system. The assessment of effects of clouds and aerosols on climate requires concerted understanding of the web of interactions formed by clouds, aerosols and terrestrial carbon and hydrological cycles. In this presentation, we will first give a brief overview of roles of clouds and aerosols in land - atmosphere interactions. We will then report new results based on simulations using the terrestrial fluxes and pools integrated simulator (FAPIS). We focus on scale and diffuse radiation effects of clouds and aerosols on vegetation - atmosphere exchanges of water vapor, sensible heat and CO2. In terms of scale effects, we will show that cloud regimes and cloud cover are both important factors in regulating land surface micrometeorology and biophysical fluxes. In terms of diffuse radiation effects, it will be demonstrated that full separations of diffuse and direct beam radiation and sunlit and shaded leaves for both photosynthesis and energy balance calculations are necessary for accurate prediction of latent heat, sensible heat and CO2 exchanges. Implications of these results for climate modeling will be discussed.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0321 Cloud/radiation interaction
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0416 Biogeophysics
SC: Biogeosciences [B]
MN: Fall Meeting 2005