| Volumes and Issues Contents of Issue 4 Special Issue |
www.biogeosciences-discuss.net/6/8279/2009/
doi:10.5194/bgd-6-8279-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Modeling the impact of drought on canopy carbon and water fluxes through parameter optimization using an ensemble Kalman filter
1International Institute for Earth System Science, Nanjing University, Nanjing 210093, China
2Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
3School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China
Abstract. Soil and atmospheric water deficits have significant influences on CO2 and energy exchanges between the atmosphere and terrestrial ecosystems. Model parameterization significantly affects the ability of a model to simulate carbon, water, and energy fluxes. In this study, an ensemble Kalman filter (EnKF) and observations of gross primary productivity (GPP) and latent heat (LE) fluxes were used to optimize model parameters significantly affecting the calculation of these fluxes for a subtropical coniferous plantation in southeastern China. The optimized parameters include the maximum carboxylation rate (Vcmax), the Ball-Berry coefficient (m) and the coefficient determining the sensitivity of stomatal conductance to atmospheric water vapor deficit D0). Optimized Vcmax and m showed larger seasonal and interannual variations than D0. Seasonal variations of Vcmax and m are more pronounced than the interannual variations. Vcmax and m are associated with soil water content (SWC). During dry periods, SWC at the 20 cm depth can explain 61% and 64% of variations of Vcmax and m, respectively. EnKF parameter optimization improves the simulations of GPP, LE and sensible heat (SH), mainly during dry periods. After parameter optimization using EnKF, the variations of GPP, LE and SH explained by the model increased by 1% to 4% at half-hourly steps and by 3% to 5% at daily time steps. Efforts are needed to develop algorithms that can properly describe the variations of these parameters under different environmental conditions.
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Citation: Ju, W., Wang, S., Yu, G., Zhou, Y., and Wang, H.: Modeling the impact of drought on canopy carbon and water fluxes through parameter optimization using an ensemble Kalman filter, Biogeosciences Discuss., 6, 8279-8309, doi:10.5194/bgd-6-8279-2009, 2009. Bibtex EndNote Reference Manager XML
