Evaluation of a non-stomatal resistance parameterization for SO2 dry deposition

Measurements of SO2 fluxes and concentrations at 5 different sites were used to study SO2 dry deposition under different canopy wetness conditions and to evaluate a non-stomatal resistance parameterization. It was found that high humidity, dew and rain increase SO2 uptake by canopy cuticles and the magnitude of the enhanced SO2 uptake by dew and rain is different. A non-stomatal resistance parameterization originally developed for O3 was applied to SO2 with adjustments to some input parameters. The modified parameterization was found to perform well compared to measurements. The non-stomatal resistance parameterization represents an improvement over other existing parameterizations due to its inclusion of meteorological variations allowing it to predict very reasonable diurnal variations of SO2 dry deposition over wet canopies.