HR: 0800h
AN: H31C-02    [Abstracts]
TI: Use of Factorial Analysis to Determine the Interaction Between Parameters of a Land Surface Model
AU: * Varejão, C G
EM: varejao@varejao.org
AF: Federal University of Viçosa, Agricultural Engineering Department, Viçosa, MG 36570000, Brazil
AU: Varejão, E V
EM: eduardo@varejao.org
AF: Federal University of Viçosa, Chemistry Department, Viçosa, MG 36570000, Brazil
AU: Costa, M H
EM: mhcosta@ufv.br
AB: Land surface models use several parameters to represent biophysical processes. These parameters frequently are unknown, reproducing with uncertainty the characteristics of the ecosystem in study. Model calibration techniques find values for each parameter that reduce uncertainty. However, the calibration process is computationally expensive, since is necessary a lot of model runs to have their parameters adjusted. The more parameters are considered, more difficult the process is, particularly when there are interactions among them, and a modification in a parameter value implies in the change of the optimum value of the other parameters. The use of a factorial experiment allows the identification of possible inert parameters, whose values do not influence the final result of the experiment and, therefore, could be excluded from the calibration process. In this work we used factorial analysis to verify the existence of interaction among 5 parameters of the land surface IBIS model - Beta2 (distribution of fine roots), Vmax (maximum Rubisco enzyme capacity), m (coefficient related to the stomatal conductance), CHS (heat capacity of stems) and CHU (heat capacity of leaves) - evaluated against the output fluxes Rn (net radiation), H (sensible heat flux), LE (latent heat flux) and NEE (net ecosystem CO2 exchange). Data was collected at the Amazon tropical rainforest site known as K83, near Santarem, Brazil. The knowledge of the existing interactions between the parameters can considerably reduce the computational cost of further optimization processes, since each parameter that does not interact with others should be optimized independently.
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1846 Model calibration (3333)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
DE: 3333 Model calibration (1846)
SC: Hydrology [H]
MN: 2007 Joint Assembly