HR: 1340h
AN: A23B-0790    [Abstracts]
TI: Nonlinear dynamics in a simple two-timescale vegetation-atmosphere system and its implications for North China drought
AU: * Wei, J
EM: jwei@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340 United States
AU: Dickinson, R E
EM: robted@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0340 United States
AU: Zeng, N
EM: zeng@atmos.umd.edu
AF: Department of Meteorology and Earth System Science Interdisciplinary Center, University of Maryland, 2421 Computer and Space Sciences Building, College Park, MD 20742-2425 United States
AB: Based on the dynamic vegetation model of a GCM, a conceptual model was constructed to describe the vegetation-atmosphere system. As the dynamic vegetation model has two timescales for vegetation growth, it revealed some mechanisms that were not revealed in one timescale models. It is indicated that areas with large atmospheric internal variability or strongly influenced by outside forcing are more vulnerable to drought. In areas with sparse initial vegetation, it is easier to fall into long term drought for vegetation with longer growth or loss timescales; while it is converse in areas with dense vegetation. GCM experiments shows that neither northern desertification nor farming experiment can simulate the drought happened in North China after the end of the 1970s. But when we combined the influences of the two, the pattern of the drought was almost simulated. This supports the conceptual model results. Farming alone can­Ýt lead to the drought because there isn­Ýt enough outside forcing to cause the drought although there is SST forcing, but it makes the system more vulnerable to drought by increasing the vegetation growth timescales. Northern desertification is an additional perturbation to drag the system to drought.
DE: 1803 Anthropogenic effects
DE: 1809 Desertification
DE: 1812 Drought
DE: 1620 Climate dynamics (3309)
DE: 0315 Biosphere/atmosphere interactions
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting