A comparison of models for deriving dry deposition fluxes of O3 and SO2 to a forest canopy

4 canopy models, representing the various classes of models that are currently used to estimate gaseous deposition to plant canopies are presented. The predictive capabilities of the models are evaluated with direct eddy correlation measurements of SO₂ and O₃ fluxes to a deciduous forest for both well-watered and water-stressed conditions. By increasing the degree of detail of the exchange-governing physical processes from the more simple single laye,: model to the more detailed multi-layer models, the predictions of the deposition rates improved by 40-50% as determined from the root mean square error (rmse). We also found by including the effect of water stress in the stomatal resistance formulations, the rmse of the predictions were decreased by generally 50% for the models that were examined.