HR: 1340h
AN: A23B-0794    [Abstracts]
TI: A Conceptual Modeling Study on Biosphere-Atmosphere Interactions and its Implications for Physically Based Climate Modeling
AU: * Wang, G
EM: gwang@engr.uconn.edu
AF: University of Connecticut, Department of Civil and Environmental Engineering 261 Glenbrook Road, Storrs, CT 06269 United States
AB: This paper presents a conceptual modeling study on the behaviors of terrestrial biosphere-atmosphere system as they relate to multiple equilibrium states and climate variability, and emphasizes their implications for physically based climate modeling. The conceptual biosphere-atmosphere model consists of equilibrium responses of vegetation and precipitation to each other, dynamics of the vegetation system, and stochastic forcing of precipitation representing the impact of atmospheric internal variability. Using precipitation as the atmospheric variable in describing the biosphere-atmosphere interactions, this model pertains to regions where biosphere productivity is limited by water. Low moisture convergence in the atmosphere combined with high sensitivity of the atmospheric climate to vegetation changes provide the most favorable condition for the existence of multiple equilibrium states. In a coupled biosphere-atmosphere system with multiple equilibria, experiments varying the stochastic forcing indicate that atmospheric internal variability is an important factor in the long term variability of the model climate and in its sensitivity to initial conditions. Specifically, the enhancement of low-frequency rainfall variability by vegetation dynamics is most pronounced with a moderate magnitude of atmospheric internal variability, and is less pronounced if internal variability is either too large or too small; detecting the existence of multiple equilibria by examining the sensitivity of the coupled model climate to initial conditions is not always reliable, since too large an internal variability reduces or even eliminates the model sensitivity to initial conditions. Findings from the conceptual model are confirmed using results from a physically based, synchronously coupled biosphere-atmosphere model.
DE: 1833 Hydroclimatology
DE: 1620 Climate dynamics (3309)
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting