HR: 1340h
AN: B53B-1191    [Abstracts]
TI: Ensemble Calibration and Sensitivity Tests of a Photosynthesis Model Using an Optimization Algorithm
AU: Xue, L
EM: lulin.xue@gmail.com
AF: Dept of Earth and Atmospheric Sci., St. Louis University, 3642 Lindell Blvd, St. Louis, MO 63108, United States
AU: * Pan, Z
EM: panz@eas.slu.edu
AF: Dept of Earth and Atmospheric Sci., St. Louis University, 3642 Lindell Blvd, St. Louis, MO 63108, United States
AB: Carbon exchange between the atmosphere and terrestrial ecosystem is a key component affecting climate changes. Except for some measurements from spotty sites, the CO2 exchange is simulated by numerical ecosystem models. These models contain large uncertainties in estimating CO2 exchange owing to incorporating a number of empirical parameters on different scales. This study applied a global optimization algorithm and ensemble approach to a surface CO2 flux scheme to 1) identify sensitive photosynthetic and respirational parameters, and 2) optimize the sensitive parameters and improve the model skills. The photosynthetic and respirational parameters of corn (C4 species) and soybean (C3 species) in NCAR land surface model (LSM) are calibrated against observations from AmeriFlux site at Boundville, IL during 1999 and 2000 growing seasons. Results showed that the most sensitive parameters are maximum carboxylation rate at 25oC and its temperature sensitivity parameter (Vcmax25 and avc), quantum efficiency at 25oC (Qe2), temperature sensitivity parameter for maintenance respiration (arm), and temperature sensitivity parameter for microbial respiration (amr). After adopting calibrated parameter values, simulated seasonal averaged CO2 fluxes were improved for both the C4 and the C3 crops (relative bias reduced from 0.09 to -0.02 for the C4 case and from 0.28 to -0.01 for the C3 case). An updated scheme incorporating new parameters and a revised flux- integration treatment is also proposed.
DE: 0402 Agricultural systems
DE: 0429 Climate dynamics (1620)
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting